synthesis chapter thesis

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• 6. Synthesize
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Synthesis Visualization

Synthesis matrix example.

• 7. Write a Literature Review

• Synthesis Worksheet

About Synthesis

Approaches to Synthesis

You can sort the literature in various ways, for example:

How to Begin?

Read your sources carefully and find the main idea(s) of each source

Look for similarities in your sources – which sources are talking about the same main ideas? (for example, sources that discuss the historical background on your topic)

Use the worksheet (above) or synthesis matrix (below) to get organized

This work can be messy. Don't worry if you have to go through a few iterations of the worksheet or matrix as you work on your lit review!

Four Examples of Student Writing

In the four examples below, only ONE shows a good example of synthesis: the fourth column, or  Student D . For a web accessible version, click the link below the image.

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From Jennifer Lim

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How to Synthesize Written Information from Multiple Sources

Shona McCombes

Content Manager

B.A., English Literature, University of Glasgow

Shona McCombes is the content manager at Scribbr, Netherlands.

Learn about our Editorial Process

Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

On This Page:

When you write a literature review or essay, you have to go beyond just summarizing the articles you’ve read – you need to synthesize the literature to show how it all fits together (and how your own research fits in).

Synthesizing simply means combining. Instead of summarizing the main points of each source in turn, you put together the ideas and findings of multiple sources in order to make an overall point.

At the most basic level, this involves looking for similarities and differences between your sources. Your synthesis should show the reader where the sources overlap and where they diverge.

Unsynthesized Example

Franz (2008) studied undergraduate online students. He looked at 17 females and 18 males and found that none of them liked APA. According to Franz, the evidence suggested that all students are reluctant to learn citations style. Perez (2010) also studies undergraduate students. She looked at 42 females and 50 males and found that males were significantly more inclined to use citation software ( p < .05). Findings suggest that females might graduate sooner. Goldstein (2012) looked at British undergraduates. Among a sample of 50, all females, all confident in their abilities to cite and were eager to write their dissertations.

Synthesized Example

Studies of undergraduate students reveal conflicting conclusions regarding relationships between advanced scholarly study and citation efficacy. Although Franz (2008) found that no participants enjoyed learning citation style, Goldstein (2012) determined in a larger study that all participants watched felt comfortable citing sources, suggesting that variables among participant and control group populations must be examined more closely. Although Perez (2010) expanded on Franz’s original study with a larger, more diverse sample…

Step 1: Organize your sources

After collecting the relevant literature, you’ve got a lot of information to work through, and no clear idea of how it all fits together.

Before you can start writing, you need to organize your notes in a way that allows you to see the relationships between sources.

One way to begin synthesizing the literature is to put your notes into a table. Depending on your topic and the type of literature you’re dealing with, there are a couple of different ways you can organize this.

Summary table

A summary table collates the key points of each source under consistent headings. This is a good approach if your sources tend to have a similar structure – for instance, if they’re all empirical papers.

Each row in the table lists one source, and each column identifies a specific part of the source. You can decide which headings to include based on what’s most relevant to the literature you’re dealing with.

For example, you might include columns for things like aims, methods, variables, population, sample size, and conclusion.

For each study, you briefly summarize each of these aspects. You can also include columns for your own evaluation and analysis.

The summary table gives you a quick overview of the key points of each source. This allows you to group sources by relevant similarities, as well as noticing important differences or contradictions in their findings.

Synthesis matrix

A synthesis matrix is useful when your sources are more varied in their purpose and structure – for example, when you’re dealing with books and essays making various different arguments about a topic.

Each column in the table lists one source. Each row is labeled with a specific concept, topic or theme that recurs across all or most of the sources.

Then, for each source, you summarize the main points or arguments related to the theme.

The purposes of the table is to identify the common points that connect the sources, as well as identifying points where they diverge or disagree.

Step 2: Outline your structure

Now you should have a clear overview of the main connections and differences between the sources you’ve read. Next, you need to decide how you’ll group them together and the order in which you’ll discuss them.

For shorter papers, your outline can just identify the focus of each paragraph; for longer papers, you might want to divide it into sections with headings.

There are a few different approaches you can take to help you structure your synthesis.

If your sources cover a broad time period, and you found patterns in how researchers approached the topic over time, you can organize your discussion chronologically .

That doesn’t mean you just summarize each paper in chronological order; instead, you should group articles into time periods and identify what they have in common, as well as signalling important turning points or developments in the literature.

If the literature covers various different topics, you can organize it thematically .

That means that each paragraph or section focuses on a specific theme and explains how that theme is approached in the literature.

Source Used with Permission: The Chicago School

If you’re drawing on literature from various different fields or they use a wide variety of research methods, you can organize your sources methodologically .

That means grouping together studies based on the type of research they did and discussing the findings that emerged from each method.

If your topic involves a debate between different schools of thought, you can organize it theoretically .

That means comparing the different theories that have been developed and grouping together papers based on the position or perspective they take on the topic, as well as evaluating which arguments are most convincing.

Step 3: Write paragraphs with topic sentences

What sets a synthesis apart from a summary is that it combines various sources. The easiest way to think about this is that each paragraph should discuss a few different sources, and you should be able to condense the overall point of the paragraph into one sentence.

This is called a topic sentence , and it usually appears at the start of the paragraph. The topic sentence signals what the whole paragraph is about; every sentence in the paragraph should be clearly related to it.

A topic sentence can be a simple summary of the paragraph’s content:

“Early research on [x] focused heavily on [y].”

For an effective synthesis, you can use topic sentences to link back to the previous paragraph, highlighting a point of debate or critique:

“Several scholars have pointed out the flaws in this approach.” “While recent research has attempted to address the problem, many of these studies have methodological flaws that limit their validity.”

By using topic sentences, you can ensure that your paragraphs are coherent and clearly show the connections between the articles you are discussing.

As you write your paragraphs, avoid quoting directly from sources: use your own words to explain the commonalities and differences that you found in the literature.

Don’t try to cover every single point from every single source – the key to synthesizing is to extract the most important and relevant information and combine it to give your reader an overall picture of the state of knowledge on your topic.

Step 4: Revise, edit and proofread

Like any other piece of academic writing, synthesizing literature doesn’t happen all in one go – it involves redrafting, revising, editing and proofreading your work.

Checklist for Synthesis

•   Do I introduce the paragraph with a clear, focused topic sentence?
•   Do I discuss more than one source in the paragraph?
•   Do I mention only the most relevant findings, rather than describing every part of the studies?
•   Do I discuss the similarities or differences between the sources, rather than summarizing each source in turn?
•   Do I put the findings or arguments of the sources in my own words?
•   Is the paragraph organized around a single idea?
•   Is the paragraph directly relevant to my research question or topic?
•   Is there a logical transition from this paragraph to the next one?

Further Information

How to Synthesise: a Step-by-Step Approach

Help…I”ve Been Asked to Synthesize!

Learn how to Synthesise (combine information from sources)

How to write a Psychology Essay

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Get Organized

• Lit Review Prep Use this template to help you evaluate your sources, create article summaries for an annotated bibliography, and a synthesis matrix for your lit review outline.

Synthesize your Information

Synthesize: combine separate elements to form a whole.

Synthesis Matrix

A synthesis matrix helps you record the main points of each source and document how sources relate to each other.

After summarizing and evaluating your sources, arrange them in a matrix or use a citation manager to help you see how they relate to each other and apply to each of your themes or variables.  

By arranging your sources by theme or variable, you can see how your sources relate to each other, and can start thinking about how you weave them together to create a narrative.

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Online Guide to Writing and Research

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Critical Strategies and Writing

One of the basic academic writing activities is researching your topic and what others have said about it. Your goal should be to draw thoughts, observations, and claims about your topic from your research. We call this process of drawing from multiple sources “ synthesis .” Click on the accordion items below for more information.

Definition, Use, and Sample Synthesis

Synthesis defined.

Synthesis Emerges from Analysis

Synthesis emerges from analytical activities we discussed on the previous page: comparative analysis and analysis for cause and effect . For example, to communicate where scholars agree and where they disagree, one must analyze their work for similarities and differences. Also crucial for understanding scholarly discourse is understanding how a particular work of scholarship shapes the scholarship of others, causing them to head in new directions.

When Should Synthesis Be Used?

When to Use Synthesis

Many college assignments require synthesis. A literature review, for example, requires that you make explanatory claims regarding a body of research. These should go beyond summary (mere description) to provide helpful characterizations that aid in understanding. Literature reviews can stand on their own, but often they are a part of a research paper, and research papers are where you will probably use synthesis most often.

The purpose of a research paper is to derive meaning from a body of information collected through research. It is your job, as the writer, to communicate that meaning to your readers. Doing this requires that you develop an informed and educated opinion of what your research suggests about your subject. Communicating this opinion requires synthesis.

Sample Synthesis

In 1655, an embassy of Dutch Jews led by Rabbi Menassah ben Israel traveled to London to meet with the Commonwealth’s new Lord Protector, Oliver Cromwell. The informal “Readmission” of Jews—who had been expelled from England by royal edict in 1290—resulting from the Whitehall conference was once hailed as a high point in the history of toleration. Yet in recent years, scholars have increasingly challenged the progressive nature of this event, both in its substance and its motivation (Kaplan 2007; Katznelson 2010; Walsham 2006) . “Toleration” in this case, as in many others, did not entail religious freedom or civic equality; Jews in England were granted legal residency and permitted to worship privately, but citizenship, public worship, and the printing of anything that “opposeth the Christian religion” remained off the cards. As for its motivation, Edward Whalley’s twofold argument was representative: the Jews “will bring in much wealth into this Commonwealth: and where wee both pray for theyre conversion and beleeve it shal be, I knowe not why wee shold deny the means” (Marshall 2006, 381–82) 

(Bejan, 2015, p. 1103).

The author of the above passage, Teresa Bejan, has synthesized the work of a number of other scholars (Kaplan, Katznelson, Walsham, and Marshall) to situate her argument.  Note how not all of these scholars are directly quoted, but they are cited because their work forms the basis of Bejan's work.

Key Takeaways

• Synthesizing allows you to carry an argument or stance you adopt within a paper in your own words, based on conclusions you have come to about the topic.
• Synthesizing contributes to confidence about your stance and topic.

Mailing Address: 3501 University Blvd. East, Adelphi, MD 20783 This work is licensed under a  Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License . © 2022 UMGC. All links to external sites were verified at the time of publication. UMGC is not responsible for the validity or integrity of information located at external sites.

Table of Contents: Online Guide to Writing

Chapter 1: College Writing

How Does College Writing Differ from Workplace Writing?

What Is College Writing?

Why So Much Emphasis on Writing?

Chapter 2: The Writing Process

Doing Exploratory Research

Getting from Notes to Your Draft

Introduction

Prewriting - Techniques to Get Started - Mining Your Intuition

Prewriting: Targeting Your Audience

Prewriting: Techniques to Get Started

Prewriting: Understanding Your Assignment

Rewriting: Being Your Own Critic

Rewriting: Creating a Revision Strategy

Rewriting: Getting Feedback

Rewriting: The Final Draft

Techniques to Get Started - Outlining

Techniques to Get Started - Using Systematic Techniques

Thesis Statement and Controlling Idea

Writing: Getting from Notes to Your Draft - Freewriting

Writing: Getting from Notes to Your Draft - Summarizing Your Ideas

Writing: Outlining What You Will Write

Chapter 3: Thinking Strategies

A Word About Style, Voice, and Tone

A Word About Style, Voice, and Tone: Style Through Vocabulary and Diction

Critical Strategies and Writing: Analysis

Critical Strategies and Writing: Evaluation

Critical Strategies and Writing: Persuasion

Critical Strategies and Writing: Synthesis

Developing a Paper Using Strategies

Kinds of Assignments You Will Write

Patterns for Presenting Information

Patterns for Presenting Information: Critiques

Patterns for Presenting Information: Discussing Raw Data

Patterns for Presenting Information: General-to-Specific Pattern

Patterns for Presenting Information: Problem-Cause-Solution Pattern

Patterns for Presenting Information: Specific-to-General Pattern

Patterns for Presenting Information: Summaries and Abstracts

Supporting with Research and Examples

Writing Essay Examinations

Writing Essay Examinations: Make Your Answer Relevant and Complete

Writing Essay Examinations: Organize Thinking Before Writing

Writing Essay Examinations: Read and Understand the Question

Chapter 4: The Research Process

Planning and Writing a Research Paper

Planning and Writing a Research Paper: Ask a Research Question

Planning and Writing a Research Paper: Cite Sources

Planning and Writing a Research Paper: Collect Evidence

Planning and Writing a Research Paper: Decide Your Point of View, or Role, for Your Research

Planning and Writing a Research Paper: Draw Conclusions

Planning and Writing a Research Paper: Find a Topic and Get an Overview

Planning and Writing a Research Paper: Manage Your Resources

Planning and Writing a Research Paper: Outline

Planning and Writing a Research Paper: Survey the Literature

Planning and Writing a Research Paper: Work Your Sources into Your Research Writing

Research Resources: Where Are Research Resources Found? - Human Resources

Research Resources: What Are Research Resources?

Research Resources: Where Are Research Resources Found?

Research Resources: Where Are Research Resources Found? - Electronic Resources

Research Resources: Where Are Research Resources Found? - Print Resources

Structuring the Research Paper: Formal Research Structure

Structuring the Research Paper: Informal Research Structure

The Nature of Research

The Research Assignment: How Should Research Sources Be Evaluated?

The Research Assignment: When Is Research Needed?

The Research Assignment: Why Perform Research?

Chapter 5: Academic Integrity

Academic Integrity

Giving Credit to Sources

Giving Credit to Sources: Copyright Laws

Giving Credit to Sources: Documentation

Giving Credit to Sources: Style Guides

Integrating Sources

Practicing Academic Integrity

Practicing Academic Integrity: Keeping Accurate Records

Practicing Academic Integrity: Managing Source Material

Practicing Academic Integrity: Managing Source Material - Paraphrasing Your Source

Practicing Academic Integrity: Managing Source Material - Quoting Your Source

Practicing Academic Integrity: Managing Source Material - Summarizing Your Sources

Types of Documentation

Types of Documentation: Bibliographies and Source Lists

Types of Documentation: Citing World Wide Web Sources

Types of Documentation: In-Text or Parenthetical Citations

Types of Documentation: In-Text or Parenthetical Citations - APA Style

Types of Documentation: In-Text or Parenthetical Citations - CSE/CBE Style

Types of Documentation: In-Text or Parenthetical Citations - Chicago Style

Types of Documentation: In-Text or Parenthetical Citations - MLA Style

Types of Documentation: Note Citations

Chapter 6: Using Library Resources

Finding Library Resources

Chapter 7: Assessing Your Writing

How Is Writing Graded?

How Is Writing Graded?: A General Assessment Tool

The Draft Stage

The Draft Stage: The First Draft

The Draft Stage: The Revision Process and the Final Draft

The Draft Stage: Using Feedback

The Research Stage

Using Assessment to Improve Your Writing

Chapter 8: Other Frequently Assigned Papers

Reviews and Reaction Papers: Article and Book Reviews

Reviews and Reaction Papers: Reaction Papers

Writing Arguments

Writing Arguments: Adapting the Argument Structure

Writing Arguments: Purposes of Argument

Writing Arguments: References to Consult for Writing Arguments

Writing Arguments: Steps to Writing an Argument - Anticipate Active Opposition

Writing Arguments: Steps to Writing an Argument - Determine Your Organization

Writing Arguments: Steps to Writing an Argument - Develop Your Argument

Writing Arguments: Steps to Writing an Argument - Introduce Your Argument

Writing Arguments: Steps to Writing an Argument - State Your Thesis or Proposition

Writing Arguments: Steps to Writing an Argument - Write Your Conclusion

Writing Arguments: Types of Argument

Appendix A: Books to Help Improve Your Writing

Dictionaries

General Style Manuals

Researching on the Internet

Special Style Manuals

Writing Handbooks

Appendix B: Collaborative Writing and Peer Reviewing

Collaborative Writing: Assignments to Accompany the Group Project

Collaborative Writing: Informal Progress Report

Collaborative Writing: Issues to Resolve

Collaborative Writing: Methodology

Collaborative Writing: Peer Evaluation

Collaborative Writing: Tasks of Collaborative Writing Group Members

Collaborative Writing: Writing Plan

General Introduction

Peer Reviewing

Appendix C: Developing an Improvement Plan

Working with Your Instructor’s Comments and Grades

Appendix D: Writing Plan and Project Schedule

Devising a Writing Project Plan and Schedule

Reviewing Your Plan with Others

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Using Evidence: Synthesis

Synthesis video playlist.

Note that these videos were created while APA 6 was the style guide edition in use. There may be some examples of writing that have not been updated to APA 7 guidelines.

Basics of Synthesis

As you incorporate published writing into your own writing, you should aim for synthesis of the material.

Synthesizing requires critical reading and thinking in order to compare different material, highlighting similarities, differences, and connections. When writers synthesize successfully, they present new ideas based on interpretations of other evidence or arguments. You can also think of synthesis as an extension of—or a more complicated form of—analysis. One main difference is that synthesis involves multiple sources, while analysis often focuses on one source.

Conceptually, it can be helpful to think about synthesis existing at both the local (or paragraph) level and the global (or paper) level.

Local Synthesis

Local synthesis occurs at the paragraph level when writers connect individual pieces of evidence from multiple sources to support a paragraph’s main idea and advance a paper’s thesis statement. A common example in academic writing is a scholarly paragraph that includes a main idea, evidence from multiple sources, and analysis of those multiple sources together.

Global Synthesis

Global synthesis occurs at the paper (or, sometimes, section) level when writers connect ideas across paragraphs or sections to create a new narrative whole. A literature review , which can either stand alone or be a section/chapter within a capstone, is a common example of a place where global synthesis is necessary. However, in almost all academic writing, global synthesis is created by and sometimes referred to as good cohesion and flow.

Synthesis in Literature Reviews

While any types of scholarly writing can include synthesis, it is most often discussed in the context of literature reviews. Visit our literature review pages for more information about synthesis in literature reviews.

Didn't find what you need? Email us at [email protected] .

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Home » Thesis – Structure, Example and Writing Guide

Thesis – Structure, Example and Writing Guide

Table of contents.

Definition:

Thesis is a scholarly document that presents a student’s original research and findings on a particular topic or question. It is usually written as a requirement for a graduate degree program and is intended to demonstrate the student’s mastery of the subject matter and their ability to conduct independent research.

History of Thesis

The concept of a thesis can be traced back to ancient Greece, where it was used as a way for students to demonstrate their knowledge of a particular subject. However, the modern form of the thesis as a scholarly document used to earn a degree is a relatively recent development.

The origin of the modern thesis can be traced back to medieval universities in Europe. During this time, students were required to present a “disputation” in which they would defend a particular thesis in front of their peers and faculty members. These disputations served as a way to demonstrate the student’s mastery of the subject matter and were often the final requirement for earning a degree.

In the 17th century, the concept of the thesis was formalized further with the creation of the modern research university. Students were now required to complete a research project and present their findings in a written document, which would serve as the basis for their degree.

The modern thesis as we know it today has evolved over time, with different disciplines and institutions adopting their own standards and formats. However, the basic elements of a thesis – original research, a clear research question, a thorough review of the literature, and a well-argued conclusion – remain the same.

Structure of Thesis

The structure of a thesis may vary slightly depending on the specific requirements of the institution, department, or field of study, but generally, it follows a specific format.

Here’s a breakdown of the structure of a thesis:

This is the first page of the thesis that includes the title of the thesis, the name of the author, the name of the institution, the department, the date, and any other relevant information required by the institution.

This is a brief summary of the thesis that provides an overview of the research question, methodology, findings, and conclusions.

This page provides a list of all the chapters and sections in the thesis and their page numbers.

Introduction

This chapter provides an overview of the research question, the context of the research, and the purpose of the study. The introduction should also outline the methodology and the scope of the research.

Literature Review

This chapter provides a critical analysis of the relevant literature on the research topic. It should demonstrate the gap in the existing knowledge and justify the need for the research.

Methodology

This chapter provides a detailed description of the research methods used to gather and analyze data. It should explain the research design, the sampling method, data collection techniques, and data analysis procedures.

This chapter presents the findings of the research. It should include tables, graphs, and charts to illustrate the results.

This chapter interprets the results and relates them to the research question. It should explain the significance of the findings and their implications for the research topic.

This chapter summarizes the key findings and the main conclusions of the research. It should also provide recommendations for future research.

This section provides a list of all the sources cited in the thesis. The citation style may vary depending on the requirements of the institution or the field of study.

This section includes any additional material that supports the research, such as raw data, survey questionnaires, or other relevant documents.

How to write Thesis

Here are some steps to help you write a thesis:

• Choose a Topic: The first step in writing a thesis is to choose a topic that interests you and is relevant to your field of study. You should also consider the scope of the topic and the availability of resources for research.
• Develop a Research Question: Once you have chosen a topic, you need to develop a research question that you will answer in your thesis. The research question should be specific, clear, and feasible.
• Conduct a Literature Review: Before you start your research, you need to conduct a literature review to identify the existing knowledge and gaps in the field. This will help you refine your research question and develop a research methodology.
• Develop a Research Methodology: Once you have refined your research question, you need to develop a research methodology that includes the research design, data collection methods, and data analysis procedures.
• Collect and Analyze Data: After developing your research methodology, you need to collect and analyze data. This may involve conducting surveys, interviews, experiments, or analyzing existing data.
• Write the Thesis: Once you have analyzed the data, you need to write the thesis. The thesis should follow a specific structure that includes an introduction, literature review, methodology, results, discussion, conclusion, and references.
• Edit and Proofread: After completing the thesis, you need to edit and proofread it carefully. You should also have someone else review it to ensure that it is clear, concise, and free of errors.
• Submit the Thesis: Finally, you need to submit the thesis to your academic advisor or committee for review and evaluation.

Example of Thesis

Example of Thesis template for Students:

Title of Thesis

Table of Contents:

Chapter 1: Introduction

Chapter 2: Literature Review

Chapter 3: Research Methodology

Chapter 4: Results

Chapter 5: Discussion

Chapter 6: Conclusion

References:

Appendices:

Note: That’s just a basic template, but it should give you an idea of the structure and content that a typical thesis might include. Be sure to consult with your department or supervisor for any specific formatting requirements they may have. Good luck with your thesis!

Application of Thesis

Thesis is an important academic document that serves several purposes. Here are some of the applications of thesis:

• Academic Requirement: A thesis is a requirement for many academic programs, especially at the graduate level. It is an essential component of the evaluation process and demonstrates the student’s ability to conduct original research and contribute to the knowledge in their field.
• Career Advancement: A thesis can also help in career advancement. Employers often value candidates who have completed a thesis as it demonstrates their research skills, critical thinking abilities, and their dedication to their field of study.
• Publication : A thesis can serve as a basis for future publications in academic journals, books, or conference proceedings. It provides the researcher with an opportunity to present their research to a wider audience and contribute to the body of knowledge in their field.
• Personal Development: Writing a thesis is a challenging task that requires time, dedication, and perseverance. It provides the student with an opportunity to develop critical thinking, research, and writing skills that are essential for their personal and professional development.
• Impact on Society: The findings of a thesis can have an impact on society by addressing important issues, providing insights into complex problems, and contributing to the development of policies and practices.

Purpose of Thesis

The purpose of a thesis is to present original research findings in a clear and organized manner. It is a formal document that demonstrates a student’s ability to conduct independent research and contribute to the knowledge in their field of study. The primary purposes of a thesis are:

• To Contribute to Knowledge: The main purpose of a thesis is to contribute to the knowledge in a particular field of study. By conducting original research and presenting their findings, the student adds new insights and perspectives to the existing body of knowledge.
• To Demonstrate Research Skills: A thesis is an opportunity for the student to demonstrate their research skills. This includes the ability to formulate a research question, design a research methodology, collect and analyze data, and draw conclusions based on their findings.
• To Develop Critical Thinking: Writing a thesis requires critical thinking and analysis. The student must evaluate existing literature and identify gaps in the field, as well as develop and defend their own ideas.
• To Provide Evidence of Competence : A thesis provides evidence of the student’s competence in their field of study. It demonstrates their ability to apply theoretical concepts to real-world problems, and their ability to communicate their ideas effectively.
• To Facilitate Career Advancement : Completing a thesis can help the student advance their career by demonstrating their research skills and dedication to their field of study. It can also provide a basis for future publications, presentations, or research projects.

When to Write Thesis

The timing for writing a thesis depends on the specific requirements of the academic program or institution. In most cases, the opportunity to write a thesis is typically offered at the graduate level, but there may be exceptions.

Generally, students should plan to write their thesis during the final year of their graduate program. This allows sufficient time for conducting research, analyzing data, and writing the thesis. It is important to start planning the thesis early and to identify a research topic and research advisor as soon as possible.

In some cases, students may be able to write a thesis as part of an undergraduate program or as an independent research project outside of an academic program. In such cases, it is important to consult with faculty advisors or mentors to ensure that the research is appropriately designed and executed.

It is important to note that the process of writing a thesis can be time-consuming and requires a significant amount of effort and dedication. It is important to plan accordingly and to allocate sufficient time for conducting research, analyzing data, and writing the thesis.

Characteristics of Thesis

The characteristics of a thesis vary depending on the specific academic program or institution. However, some general characteristics of a thesis include:

• Originality : A thesis should present original research findings or insights. It should demonstrate the student’s ability to conduct independent research and contribute to the knowledge in their field of study.
• Clarity : A thesis should be clear and concise. It should present the research question, methodology, findings, and conclusions in a logical and organized manner. It should also be well-written, with proper grammar, spelling, and punctuation.
• Research-Based: A thesis should be based on rigorous research, which involves collecting and analyzing data from various sources. The research should be well-designed, with appropriate research methods and techniques.
• Evidence-Based : A thesis should be based on evidence, which means that all claims made in the thesis should be supported by data or literature. The evidence should be properly cited using appropriate citation styles.
• Critical Thinking: A thesis should demonstrate the student’s ability to critically analyze and evaluate information. It should present the student’s own ideas and arguments, and engage with existing literature in the field.
• Academic Style : A thesis should adhere to the conventions of academic writing. It should be well-structured, with clear headings and subheadings, and should use appropriate academic language.

Advantages of Thesis

There are several advantages to writing a thesis, including:

• Development of Research Skills: Writing a thesis requires extensive research and analytical skills. It helps to develop the student’s research skills, including the ability to formulate research questions, design and execute research methodologies, collect and analyze data, and draw conclusions based on their findings.
• Contribution to Knowledge: Writing a thesis provides an opportunity for the student to contribute to the knowledge in their field of study. By conducting original research, they can add new insights and perspectives to the existing body of knowledge.
• Preparation for Future Research: Completing a thesis prepares the student for future research projects. It provides them with the necessary skills to design and execute research methodologies, analyze data, and draw conclusions based on their findings.
• Career Advancement: Writing a thesis can help to advance the student’s career. It demonstrates their research skills and dedication to their field of study, and provides a basis for future publications, presentations, or research projects.
• Personal Growth: Completing a thesis can be a challenging and rewarding experience. It requires dedication, hard work, and perseverance. It can help the student to develop self-confidence, independence, and a sense of accomplishment.

Limitations of Thesis

There are also some limitations to writing a thesis, including:

• Time and Resources: Writing a thesis requires a significant amount of time and resources. It can be a time-consuming and expensive process, as it may involve conducting original research, analyzing data, and producing a lengthy document.
• Narrow Focus: A thesis is typically focused on a specific research question or topic, which may limit the student’s exposure to other areas within their field of study.
• Limited Audience: A thesis is usually only read by a small number of people, such as the student’s thesis advisor and committee members. This limits the potential impact of the research findings.
• Lack of Real-World Application : Some thesis topics may be highly theoretical or academic in nature, which may limit their practical application in the real world.
• Pressure and Stress : Writing a thesis can be a stressful and pressure-filled experience, as it may involve meeting strict deadlines, conducting original research, and producing a high-quality document.
• Potential for Isolation: Writing a thesis can be a solitary experience, as the student may spend a significant amount of time working independently on their research and writing.

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Muhammad Hassan

Researcher, Academic Writer, Web developer

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• Knowledge Base
• Dissertation

How to Write a Thesis or Dissertation Conclusion

Published on September 6, 2022 by Tegan George and Shona McCombes. Revised on November 20, 2023.

The conclusion is the very last part of your thesis or dissertation . It should be concise and engaging, leaving your reader with a clear understanding of your main findings, as well as the answer to your research question .

In it, you should:

• Clearly state the answer to your main research question
• Summarize and reflect on your research process
• Make recommendations for future work on your thesis or dissertation topic
• Show what new knowledge you have contributed to your field
• Wrap up your thesis or dissertation

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Table of contents

Discussion vs. conclusion, how long should your conclusion be, step 1: answer your research question, step 2: summarize and reflect on your research, step 3: make future recommendations, step 4: emphasize your contributions to your field, step 5: wrap up your thesis or dissertation, full conclusion example, conclusion checklist, other interesting articles, frequently asked questions about conclusion sections.

While your conclusion contains similar elements to your discussion section , they are not the same thing.

Your conclusion should be shorter and more general than your discussion. Instead of repeating literature from your literature review , discussing specific research results , or interpreting your data in detail, concentrate on making broad statements that sum up the most important insights of your research.

As a rule of thumb, your conclusion should not introduce new data, interpretations, or arguments.

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Depending on whether you are writing a thesis or dissertation, your length will vary. Generally, a conclusion should make up around 5–7% of your overall word count.

An empirical scientific study will often have a short conclusion, concisely stating the main findings and recommendations for future research. A humanities dissertation topic or systematic review , on the other hand, might require more space to conclude its analysis, tying all the previous sections together in an overall argument.

Your conclusion should begin with the main question that your thesis or dissertation aimed to address. This is your final chance to show that you’ve done what you set out to do, so make sure to formulate a clear, concise answer.

• Don’t repeat a list of all the results that you already discussed
• Do synthesize them into a final takeaway that the reader will remember.

An empirical thesis or dissertation conclusion may begin like this:

A case study –based thesis or dissertation conclusion may begin like this:

In the second example, the research aim is not directly restated, but rather added implicitly to the statement. To avoid repeating yourself, it is helpful to reformulate your aims and questions into an overall statement of what you did and how you did it.

Your conclusion is an opportunity to remind your reader why you took the approach you did, what you expected to find, and how well the results matched your expectations.

To avoid repetition , consider writing more reflectively here, rather than just writing a summary of each preceding section. Consider mentioning the effectiveness of your methodology , or perhaps any new questions or unexpected insights that arose in the process.

You can also mention any limitations of your research, but only if you haven’t already included these in the discussion. Don’t dwell on them at length, though—focus on the positives of your work.

• While x limits the generalizability of the results, this approach provides new insight into y .
• This research clearly illustrates x , but it also raises the question of y .

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You may already have made a few recommendations for future research in your discussion section, but the conclusion is a good place to elaborate and look ahead, considering the implications of your findings in both theoretical and practical terms.

• Based on these conclusions, practitioners should consider …
• To better understand the implications of these results, future studies could address …
• Further research is needed to determine the causes of/effects of/relationship between …

When making recommendations for further research, be sure not to undermine your own work. Relatedly, while future studies might confirm, build on, or enrich your conclusions, they shouldn’t be required for your argument to feel complete. Your work should stand alone on its own merits.

Just as you should avoid too much self-criticism, you should also avoid exaggerating the applicability of your research. If you’re making recommendations for policy, business, or other practical implementations, it’s generally best to frame them as “shoulds” rather than “musts.” All in all, the purpose of academic research is to inform, explain, and explore—not to demand.

Make sure your reader is left with a strong impression of what your research has contributed to the state of your field.

Some strategies to achieve this include:

• Returning to your problem statement to explain how your research helps solve the problem
• Referring back to the literature review and showing how you have addressed a gap in knowledge
• Discussing how your findings confirm or challenge an existing theory or assumption

Again, avoid simply repeating what you’ve already covered in the discussion in your conclusion. Instead, pick out the most important points and sum them up succinctly, situating your project in a broader context.

The end is near! Once you’ve finished writing your conclusion, it’s time to wrap up your thesis or dissertation with a few final steps:

• It’s a good idea to write your abstract next, while the research is still fresh in your mind.
• Next, make sure your reference list is complete and correctly formatted. To speed up the process, you can use our free APA citation generator .
• Once you’ve added any appendices , you can create a table of contents and title page .
• Finally, read through the whole document again to make sure your thesis is clearly written and free from language errors. You can proofread it yourself , ask a friend, or consider Scribbr’s proofreading and editing service .

Here is an example of how you can write your conclusion section. Notice how it includes everything mentioned above:

V. Conclusion

The current research aimed to identify acoustic speech characteristics which mark the beginning of an exacerbation in COPD patients.

The central questions for this research were as follows: 1. Which acoustic measures extracted from read speech differ between COPD speakers in stable condition and healthy speakers? 2. In what ways does the speech of COPD patients during an exacerbation differ from speech of COPD patients during stable periods?

All recordings were aligned using a script. Subsequently, they were manually annotated to indicate respiratory actions such as inhaling and exhaling. The recordings of 9 stable COPD patients reading aloud were then compared with the recordings of 5 healthy control subjects reading aloud. The results showed a significant effect of condition on the number of in- and exhalations per syllable, the number of non-linguistic in- and exhalations per syllable, and the ratio of voiced and silence intervals. The number of in- and exhalations per syllable and the number of non-linguistic in- and exhalations per syllable were higher for COPD patients than for healthy controls, which confirmed both hypotheses.

However, the higher ratio of voiced and silence intervals for COPD patients compared to healthy controls was not in line with the hypotheses. This unpredicted result might have been caused by the different reading materials or recording procedures for both groups, or by a difference in reading skills. Moreover, there was a trend regarding the effect of condition on the number of syllables per breath group. The number of syllables per breath group was higher for healthy controls than for COPD patients, which was in line with the hypothesis. There was no effect of condition on pitch, intensity, center of gravity, pitch variability, speaking rate, or articulation rate.

This research has shown that the speech of COPD patients in exacerbation differs from the speech of COPD patients in stable condition. This might have potential for the detection of exacerbations. However, sustained vowels rarely occur in spontaneous speech. Therefore, the last two outcome measures might have greater potential for the detection of beginning exacerbations, but further research on the different outcome measures and their potential for the detection of exacerbations is needed due to the limitations of the current study.

Checklist: Conclusion

I have clearly and concisely answered the main research question .

I have summarized my overall argument or key takeaways.

I have mentioned any important limitations of the research.

I have given relevant recommendations .

I have clearly explained what my research has contributed to my field.

I have  not introduced any new data or arguments.

You've written a great conclusion! Use the other checklists to further improve your dissertation.

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In a thesis or dissertation, the discussion is an in-depth exploration of the results, going into detail about the meaning of your findings and citing relevant sources to put them in context.

The conclusion is more shorter and more general: it concisely answers your main research question and makes recommendations based on your overall findings.

While it may be tempting to present new arguments or evidence in your thesis or disseration conclusion , especially if you have a particularly striking argument you’d like to finish your analysis with, you shouldn’t. Theses and dissertations follow a more formal structure than this.

All your findings and arguments should be presented in the body of the text (more specifically in the discussion section and results section .) The conclusion is meant to summarize and reflect on the evidence and arguments you have already presented, not introduce new ones.

For a stronger dissertation conclusion , avoid including:

• Important evidence or analysis that wasn’t mentioned in the discussion section and results section
• Generic concluding phrases (e.g. “In conclusion …”)
• Weak statements that undermine your argument (e.g., “There are good points on both sides of this issue.”)

Your conclusion should leave the reader with a strong, decisive impression of your work.

The conclusion of your thesis or dissertation shouldn’t take up more than 5–7% of your overall word count.

The conclusion of your thesis or dissertation should include the following:

• A restatement of your research question
• A summary of your key arguments and/or results
• A short discussion of the implications of your research

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Synthesizing Sources

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When you look for areas where your sources agree or disagree and try to draw broader conclusions about your topic based on what your sources say, you are engaging in synthesis. Writing a research paper usually requires synthesizing the available sources in order to provide new insight or a different perspective into your particular topic (as opposed to simply restating what each individual source says about your research topic).

Note that synthesizing is not the same as summarizing.  

• A summary restates the information in one or more sources without providing new insight or reaching new conclusions.
• A synthesis draws on multiple sources to reach a broader conclusion.

There are two types of syntheses: explanatory syntheses and argumentative syntheses . Explanatory syntheses seek to bring sources together to explain a perspective and the reasoning behind it. Argumentative syntheses seek to bring sources together to make an argument. Both types of synthesis involve looking for relationships between sources and drawing conclusions.

In order to successfully synthesize your sources, you might begin by grouping your sources by topic and looking for connections. For example, if you were researching the pros and cons of encouraging healthy eating in children, you would want to separate your sources to find which ones agree with each other and which ones disagree.

After you have a good idea of what your sources are saying, you want to construct your body paragraphs in a way that acknowledges different sources and highlights where you can draw new conclusions.

As you continue synthesizing, here are a few points to remember:

• Don’t force a relationship between sources if there isn’t one. Not all of your sources have to complement one another.
• Do your best to highlight the relationships between sources in very clear ways.
• Don’t ignore any outliers in your research. It’s important to take note of every perspective (even those that disagree with your broader conclusions).

Example Syntheses

Below are two examples of synthesis: one where synthesis is NOT utilized well, and one where it is.

Parents are always trying to find ways to encourage healthy eating in their children. Elena Pearl Ben-Joseph, a doctor and writer for KidsHealth , encourages parents to be role models for their children by not dieting or vocalizing concerns about their body image. The first popular diet began in 1863. William Banting named it the “Banting” diet after himself, and it consisted of eating fruits, vegetables, meat, and dry wine. Despite the fact that dieting has been around for over a hundred and fifty years, parents should not diet because it hinders children’s understanding of healthy eating.

In this sample paragraph, the paragraph begins with one idea then drastically shifts to another. Rather than comparing the sources, the author simply describes their content. This leads the paragraph to veer in an different direction at the end, and it prevents the paragraph from expressing any strong arguments or conclusions.

An example of a stronger synthesis can be found below.

Parents are always trying to find ways to encourage healthy eating in their children. Different scientists and educators have different strategies for promoting a well-rounded diet while still encouraging body positivity in children. David R. Just and Joseph Price suggest in their article “Using Incentives to Encourage Healthy Eating in Children” that children are more likely to eat fruits and vegetables if they are given a reward (855-856). Similarly, Elena Pearl Ben-Joseph, a doctor and writer for Kids Health , encourages parents to be role models for their children. She states that “parents who are always dieting or complaining about their bodies may foster these same negative feelings in their kids. Try to keep a positive approach about food” (Ben-Joseph). Martha J. Nepper and Weiwen Chai support Ben-Joseph’s suggestions in their article “Parents’ Barriers and Strategies to Promote Healthy Eating among School-age Children.” Nepper and Chai note, “Parents felt that patience, consistency, educating themselves on proper nutrition, and having more healthy foods available in the home were important strategies when developing healthy eating habits for their children.” By following some of these ideas, parents can help their children develop healthy eating habits while still maintaining body positivity.

In this example, the author puts different sources in conversation with one another. Rather than simply describing the content of the sources in order, the author uses transitions (like "similarly") and makes the relationship between the sources evident.

• Welcome to Chapter 2

How to Critically Analyze Sources

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What D oes Synthesis and Analysis Mean?

Synthesis: the combination of ideas to

• show commonalities or patterns

Analysis: a detailed examination

• of elements, ideas, or the structure of something
• can be a basis for discussion or interpretation

Synthesis and Analysis: combine and examine ideas to

• show how commonalities, patterns, and elements fit together
• form a unified point for a theory, discussion, or interpretation
• develop an informed evaluation of the idea by presenting several different viewpoints and/or ideas
• Article Spreadsheet Example (Article Organization Matrix) Use this spreadsheet to help you organize your articles as you research your topic.

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Chapter Six: Analysis and Synthesis

What does it mean to know something? How would you explain the process of thinking? In the 1950s, educational theorist Benjamin Bloom proposed that human cognition, thinking and knowing, could be classified by six categories. 1 Hierarchically arranged in order of complexity, these steps were:

Since his original model, the taxonomy has been revised, as illustrated in the diagram below:

• Each word is an action verb instead of a noun (e.g., “applying” instead of “application”);
• Some words have been changed for different synonyms;
• One version holds “creating” above “evaluating”;
• And, most importantly, other versions are reshaped into a circle, as pictured above. 2

What do you think the significance of these changes is?

I introduce this model of cognition to contextualize analysis as a cognitive tool which can work in tandem with other cognitive tasks and behaviors. Analysis is most commonly used alongside synthesis . To proceed with the LEGO® example from Chapter 4, consider my taking apart the castle as an act of analysis. I study each face of each block intently, even those parts that I can’t see when the castle is fully constructed. In the process of synthesis, I bring together certain blocks from the castle to instead build something else—let’s say, a racecar. By unpacking and interpreting each part , I’m able to build a new whole . 3

In a text wrestling essay, you’re engaging in a process very similar to my castle-to-racecar adventure. You’ll encounter a text and unpack it attentively, looking closely at each piece of language, its arrangement, its signification, and then use it to build an insightful, critical insight about the original text. I might not use every original block, but by exploring the relationship of part-to-whole, I better understand how the castle is a castle. In turn, I am better positioned to act as a sort of tour guide for the castle or a mechanic for the racecar, able to show my readers what about the castle or racecar is important and to explain how it works.

In this chapter, you’ll learn about crafting a thesis for a text wrestling essay and using evidence to support that thesis . As you will discover, an analytical essay involves every tier of Bloom’s Taxonomy, arguably even including “judgement” because your thesis will present an interpretation that is evidence-based and arguable.

Chapter Vocabulary

So What? Turning Observations into a Thesis

It’s likely that you’ve heard the term “thesis statement” multiple times in your writing career. Even though you may have some idea what a thesis entails already, it is worth reviewing and unpacking the expectations surrounding a thesis, specifically in a text wrestling essay.

A thesis statement is a central, unifying insight that drives your analysis or argument. In a typical college essay, this insight should be articulated in one to three sentences, placed within the introductory paragraph or section. As we’ll see below, this is not always the case, but it is what many of your audiences will expect. To put it simply, a thesis is the “So what?” of an analytical or persuasive essay. It answers your audience when they ask, Why does your writing matter? What bigger insights does it yield about the subject of analysis? About our world?

Thesis statements in most rhetorical situations advocate for a certain vision of a text, phenomenon, reality, or policy. Good thesis statements support such a vision using evidence and thinking that confirms, clarifies, demonstrates, nuances, or otherwise relates to that vision. In other words, a thesis is “a proposition that you can prove with evidence…, yet it’s one you have to prove, that isn’t obviously true or merely factual.” 4

In a text wrestling analysis, a thesis pushes beyond basic summary and observation. In other words, it’s the difference between:

If you think of your essay as the human body, the thesis is the spine. Yes, the body can still exist without a spine, but its functionings will be severely limited. Furthermore, everything comes back to and radiates out from the spine: trace back from your fingertips to your backbone and consider how they relate. In turn, each paragraph should tie back to your thesis, offering support and clear connections so your reader can see the entire “body” of your essay. In this way, a thesis statement serves two purposes: it is not only about the ideas of your paper, but also the structure .

The Purdue Online Writing Lab (OWL) 5 suggests this specific process for developing your thesis statement:

• Once you’ve read the story or novel closely, look back over your notes for patterns of questions or ideas that interest you. Have most of your questions been about the characters, how they develop or change?

For example: If you are reading Conrad’s  The Secret Agent , do you seem to be most interested in what the author has to say about society? Choose a pattern of ideas and express it in the form of a question and an answer such as the following:

Question:  What does Conrad seem to be suggesting about early twentieth-century London society in his novel  The Secret Agent ? Answer:  Conrad suggests that all classes of society are corrupt.

Pitfalls: Choosing too many ideas. Choosing an idea without any support.

• Once you have some general points to focus on, write your possible ideas and answer the questions that they suggest.

For example: Question :  How does Conrad develop the idea that all classes of society are corrupt? Answer:  He uses images of beasts and cannibalism whether he’s describing socialites, policemen or secret agents.

• To write your thesis statement, all you have to do is turn the question and answer around. You’ve already given the answer, now just put it in a sentence (or a couple of sentences) so that the thesis of your paper is clear.

For example: In his novel,  The Secret Agent , Conrad uses beast and cannibal imagery to describe the characters and their relationships to each other. This pattern of images suggests that Conrad saw corruption in every level of early twentieth-century London society.

• Now that you’re familiar with the story or novel and have developed a thesis statement, you’re ready to choose the evidence you’ll use to support your thesis. There are a lot of good ways to do this, but all of them depend on a strong thesis for their direction.

For example: Here’s a student’s thesis about Joseph Conrad’s  The Secret Agent .

In his novel, The Secret Agent, Conrad uses beast and cannibal imagery to describe the characters and their relationships to each other. This pattern of images suggests that Conrad saw corruption in every level of early twentieth-century London society.

This thesis focuses on the idea of social corruption and the device of imagery. To support this thesis, you would need to find images of beasts and cannibalism within the text.

There are many ways to write a thesis, and your construction of a thesis statement will become more intuitive and nuanced as you become a more confident and competent writer. However, there are a few tried-and-true strategies that I’ll share with you over the next few pages.

The T3 Strategy

T3 is a formula to create a thesis statement. The T (for Thesis) should be the point you’re trying to make—the “So what?” In a text wrestling analysis, you are expected to advocate for a certain interpretation of a text: this is your “So what?” Examples might include:

In “A Wind from the North,” Bill Capossere conveys the loneliness of isolated life or Kate Chopin’s “The Story of an Hour” suggests that marriage can be oppressive to women

But wait—there’s more! In a text wrestling analysis, your interpretation must be based on evidence from that text. Therefore, your thesis should identify both a focused statement of the interpretation (the whole) and also the particular subjects of your observation (the parts of the text you will focus on support that interpretation). A complete T3 thesis statement for a text wrestling analysis might look more like this:

In “A Wind from the North,” Bill Capossere conveys the loneliness of an isolated lifestyle using the motif of snow, the repeated phrase “five or six days” (104), and the symbol of his uncle’s car. or “The Story of an Hour” suggests that marriage can be oppressive to women. To demonstrate this theme, Kate Chopin integrates irony, foreshadowing, and symbols of freedom in the story.

Notice the way the T3 allows for the part-to-whole thinking that underlies analysis:

This is also a useful strategy because it can provide structure for your paper: each justifying support for your thesis should be one section of your paper.

• Thesis: In “A Wind from the North,” Bill Capossere conveys the loneliness of an isolated lifestyle using the motif of snow, the repeated phrase “five or six days” (104), and the symbol of his uncle’s car.
• Section on ‘the motif of snow.’ Topic sentence: The recurring imagery of snow creates a tone of frostiness and demonstrates the passage of time.
• Section on ‘the repeated phrase “five or six days” (104).’ Topic sentence: When Capossere repeats “five or six days” (104), he reveals the ambiguity of death in a life not lived.
• Section on ‘the symbol of his uncle’s car.’ Topic sentence: Finally, Capossere’s uncle’s car is symbolic of his lifestyle.

Once you’ve developed a T3 statement, you can revise it to make it feel less formulaic. For example:

In “A Wind from the North,” Bill Capossere conveys the loneliness of an isolated lifestyle by symbolizing his uncle with a “untouchable” car. Additionally, he repeats images and phrases in the essay to reinforce his uncle’s isolation. or “The Story of an Hour,” a short story by Kate Chopin, uses a plot twist to imply that marriage can be oppressive to women. The symbols of freedom in the story create a feeling of joy, but the attentive reader will recognize the imminent irony.

The O/P Strategy

An occasion/position thesis statement is rhetorically convincing because it explains the relevance of your argument and concisely articulates that argument. Although you should already have your position in mind, your rhetorical occasion will lead this statement off: what sociohistorical conditions make your writing timely, relevant, applicable? Continuing with the previous examples:

As our society moves from individualism to isolationism, Bill Capossere’s “A Wind from the North” is a salient example of a life lived alone. or Although Chopin’s story was written over 100 years ago, it still provides insight to gender dynamics in American marriages.

Following your occasion, state your position—again, this is your “So What?” It is wise to include at least some preview of the parts you will be examining.

As our society moves from individualism to isolationism, Bill Capossere’s “A Wind from the North” is a salient example of a life lived alone. Using recurring images and phrases, Capossere conveys the loneliness of his uncle leading up to his death. or Although Chopin’s story was written over 100 years ago, it still provides insight to gender dynamics in American marriages. “The Story of an Hour” reminds us that marriage has historically meant a surrender of freedom for women.

Research Question and Embedded Thesis

There’s one more common style of thesis construction that’s worth noting, and that’s the inquiry-based thesis. (Read more about inquiry-based research writing in Chapter Eight). For this thesis, you’ll develop an incisive and focused question which you’ll explore throughout the course of the essay. By the end of the essay, you will be able to offer an answer (perhaps a complicated or incomplete answer, but still some kind of answer) to the question. This form is also referred to as the “embedded thesis” or “delayed thesis” organization.

Although this model of thesis can be effectively applied in a text wrestling essay, it is often more effective when combined with one of the other methods above.

Consider the following examples:

Bill Capossere’s essay “A Wind from the North” suggests that isolation results in sorrow and loneliness; is this always the case? How does Capossere create such a vision of his uncle’s life? or Many people would believe that Kate Chopin’s story reflects an outdated perception of marriage—but can “The Story of an Hour” reveal power imbalances in modern relationships, too?

Synthesis: Using Evidence to Explore Your Thesis

Now that you’ve considered what your analytical insight might be (articulated in the form of a thesis), it’s time to bring evidence in to support your analysis—this is the synthesis part of Bloom’s Taxonomy earlier in this chapter. Synthesis refers to the creation of a new whole (an interpretation) using smaller parts (evidence from the text you’ve analyzed).

There are essentially two ways to go about collecting and culling relevant support from the text with which you’re wrestling. In my experience, students are split about evenly on which option is better for them:

Option #1: Before writing your thesis, while you’re reading and rereading your text, annotate the page and take notes. Copy down quotes, images, formal features, and themes that are striking, exciting, or relatable. Then, try to group your collection of evidence according to common traits. Once you’ve done so, choose one or two groups on which to base your thesis. Or Option #2: After writing your thesis , revisit the text looking for quotes, images, and themes that support, elaborate, or explain your interpretation. Record these quotes, and then return to the drafting process.

Once you’ve gathered evidence from your focus text, you should weave quotes, paraphrases, and summaries into your own writing. A common misconception is that you should write “around” your evidence, i.e. choosing the direct quote you want to use and building a paragraph around it. Instead, you should foreground your interpretation and analysis, using evidence in the background to explore and support that interpretation. Lead with your idea, then demonstrate it with evidence; then, explain how your evidence demonstrates your idea.

The appropriate ratio of evidence (their writing) to exposition (your writing) will vary depending on your rhetorical situation, but I advise my students to spend at least as many words unpacking a quote as that quote contains. (I’m referring here to Step #4 in the table below.) For example, if you use a direct quote of 25 words, you ought to spend at least 25 words explaining how that quote supports or nuances your interpretation.

There are infinite ways to bring evidence into your discussion, 6 but for now, let’s take a look at a formula that many students find productive as they find their footing in analytical writing: Front-load + Quote/Paraphrase/Summarize + Cite + Explain/elaborate/analyze.

What might this look like in practice?

The recurring imagery of snow creates a tone of frostiness and demonstrates the passage of time. (1) Snow brings to mind connotations of wintery cold, quiet, and death (2) as a “sky of utter clarity and simplicity” lingers over his uncle’s home and “it [begins] once more to snow” ( (3) Capossere 104). (4) Throughout his essay, Capossere returns frequently to weather imagery, but snow especially, to play on associations the reader has. In this line, snow sets the tone by wrapping itself in with “clarity,” a state of mind. Even though the narrator still seems ambivalent about his uncle, this clarity suggests that he is reflecting with a new and somber understanding.

• Front-load Snow brings to mind connotations of wintery cold, quiet, and death
• Quote as a “sky of utter clarity and simplicity” lingers over his uncle’s home and “it [begins] once more to snow”
• Cite (Capossere 104).
• Explain/elaborate/analysis Throughout his essay, Capossere returns frequently to weather imagery, but snow especially, to play on associations the reader has. In this line, snow sets the tone by wrapping itself in with “clarity,” a state of mind. Even though the narrator still seems ambivalent about his uncle, this clarity suggests that he is reflecting with a new and somber understanding.

This might feel formulaic and forced at first, but following these steps will ensure that you give each piece of evidence thorough attention. Some teachers call this method a “quote sandwich” because you put your evidence between two slices of your own language and interpretation.

For more on front-loading (readerly signposts or signal phrases), see the subsection titled “Readerly Signposts” in Chapter Nine.

Idea Generation: Close Reading Graphic Organizer

The first time you read a text, you most likely will not magically stumble upon a unique, inspiring insight to pursue as a thesis. As discussed earlier in this section, close reading is an iterative process, which means that you must repeatedly encounter a text (reread, re-watch, re-listen, etc.) trying to challenge it, interrogate it, and gradually develop a working thesis.

Very often, the best way to practice analysis is collaboratively, through discussion. Because other people will necessarily provide different perspectives through their unique interpretive positions, reading groups can help you grow your analysis. By discussing a text, you open yourself up to more nuanced and unanticipated interpretations influenced by your peers. Your teacher might ask you to work in small groups to complete the following graphic organizer in response to a certain text. (You can also complete this exercise independently, but it might not yield the same results.)

Thesis Builder

Your thesis statement can and should evolve as you continue writing your paper: teachers will often refer to a thesis as a “working thesis” because the revision process should include tweaking, pivoting, focusing, expanding, and/or rewording your thesis. The exercise on the next two pages, though, should help you develop a working thesis to begin your project. Following the examples, identify the components of your analysis that might contribute to a thesis statement.

Model Texts by Student Authors

(A text wrestling analysis of “Proofs” by Richard Rodriguez)

Songs are culturally important. In the short story “Proofs” by Richard Rodriguez, a young Mexican American man comes to terms with his bi-cultural life. This young man’s father came to America from a small and poverty-stricken Mexican village. The young man flashes from his story to his father’s story in order to explore his Mexican heritage and American life. Midway through the story Richard Rodriguez utilizes the analogies of songs to represent the cultures and how they differ. Throughout the story there is a clash of cultures. Because culture can be experienced through the arts and teachings of a community, Rodriguez uses the songs of the two cultures to represent the protagonist’s bi-cultural experience.

According to Rodriguez, the songs that come from Mexico express an emotional and loving culture and community: “But my mama says there are no songs like the love songs of Mexico” (50). The songs from that culture can be beautiful. It is amazing the love and beauty that come from social capital and community involvement. The language Richard Rodriguez uses to explain these songs is beautiful as well. “—it is the raw edge of sentiment” (51). The author explains how it is the men who keep the songs. No matter how stoic the men are, they have an outlet to express their love and pain as well as every emotion in between. “The cry of a Jackal under the moon, the whistle of a phallus, the maniacal song of the skull” (51). This is an outlet for men to express themselves that is not prevalent in American culture. It expresses a level of love and intimacy between people that is not a part of American culture. The songs from the American culture are different. In America the songs get lost. There is assimilation of cultures. The songs of Mexico are important to the protagonist of the story. There is a clash between the old culture in Mexico and the subject’s new American life represented in these songs.

A few paragraphs later in the story, on page 52, the author tells us the difference in the American song. America sings a different tune. America is the land of opportunity. It represents upward mobility and the ability to “make it or break it.” But it seems there is a cost for all this material gain and all this opportunity. There seems to be a lack of love and emotion, a lack of the ability to express pain and all other feelings, the type of emotion which is expressed in the songs of Mexico. The song of America says, “You can be anything you want to be” (52). The song represents the American Dream. The cost seems to be the loss of compassion, love and emotion that is expressed through the songs of Mexico. There is no outlet quite the same for the stoic men of America. Rodriguez explains how the Mexican migrant workers have all that pain and desire, all that emotion penned up inside until it explodes in violent outbursts. “Or they would come into town on Monday nights for the wrestling matches or on Tuesdays for boxing. They worked over in Yolo County. They were men without women. They were Mexicans without Mexico” (49).

Rodriguez uses the language in the story almost like a song in order to portray the culture of the American dream. The phrase “I will send for you or I will come home rich,” is repeated twice throughout the story. The gain for all this loss of love and compassion is the dream of financial gain. “You have come into the country on your knees with your head down. You are a man” (48). That is the allure of the American Dream.

The protagonist of the story was born in America. Throughout the story he is looking at this illusion of the American Dream through a different frame. He is also trying to come to terms with his own manhood in relation to his American life and Mexican heritage. The subject has the ability to see the two songs in a different light. “The city will win. The city will give the children all the village could not-VCR’s, hairstyles, drumbeat. The city sings mean songs, dirty songs” (52). Part of the subject’s reconciliation process with himself is seeing that all the material stuff that is dangled as part of the American Dream is not worth the love and emotion that is held in the old Mexican villages and expressed in their songs.

Rodriguez represents this conflict of culture on page 53. The protagonist of the story is taking pictures during the arrest of illegal border-crossers. “I stare at the faces. They stare at me. To them I am not bearing witness; I am part of the process of being arrested”(53). The subject is torn between the two cultures in a hazy middle ground. He is not one of the migrants and he is not one of the police. He is there taking pictures of the incident with a connection to both of the groups and both of the groups see him connected with the other.

The old Mexican villages are characterized by a lack of : “Mexico is poor” (50). However, this is not the reason for the love and emotion that is held. The thought that people have more love and emotion because they are poor is a misconception. There are both rich people and poor people who have multitudes of love and compassion. The defining elements in creating love and emotion for each other comes from the level of community interaction and trust—the ability to sing these love songs and express emotion towards one another. People who become caught up in the American Dream tend to be obsessed with their own personal gain. This diminishes the social interaction and trust between fellow humans. There is no outlet in the culture of America quite the same as singing love songs towards each other. It does not matter if they are rich or poor, lack of community, trust, and social interaction; lack of songs can lead to lack of love and emotion that is seen in the old songs of Mexico.

The image of the American Dream is bright and shiny. To a young boy in a poor village the thought of power and wealth can dominate over a life of poverty with love and emotion. However, there is poverty in America today as well as in Mexico. The poverty here looks a little different but many migrants and young men find the American Dream to be an illusion. “Most immigrants to America came from villages.

The America that Mexicans find today, at the decline of the century, is a closed-circuit city of ramps and dark towers, a city without God. The city is evil. Turn. Turn” (50). The song of America sings an inviting tune for young men from poor villages. When they arrive though it is not what they dreamed about. The subject of the story can see this. He is trying to come of age in his own way, acknowledging America and the Mexico of old. He is able to look back and forth in relation to the America his father came to for power and wealth and the America that he grew up in. All the while, he watches this migration of poor villages, filled with love and emotion, to a big heartless city, while referring back to his father’s memory of why he came to America and his own memories of growing up in America. “Like wandering Jews. They carried their home with them, back and forth: they had no true home but the tabernacle of memory” (51). The subject of the story is experiencing all of this conflict of culture and trying to compose his own song.

Works Cited

Rodriguez, Richard. “Proofs.” In Short: A Collection of Brief Creative Nonfiction , edited by Judith Kitchen and Mary Paumier Jones, Norton, 1996, pp. 48-54.

Normal Person: An Analysis of the Standards of Normativity in “A Plague of Tics” 9

David Sedaris’ essay “A Plague of Tics” describes Sedaris’ psychological struggles he encountered in his youth, expressed through obsessive-compulsive tics. These abnormal behaviors heavily inhibited his functionings, but more importantly, isolated and embarrassed him during his childhood, adolescence, and young adult years. Authority figures in his life would mock him openly, and he constantly struggled to perform routine simple tasks in a timely manner, solely due to the amount of time that needed to be set aside for carrying out these compulsive tics. He lacked the necessary social support an adolescent requires because of his apparent abnormality. But when we look at the behaviors of his parents, as well as the socially acceptable tics of our society more generally, we see how Sedaris’ tics are in fact not too different, if not less harmful than those of the society around him. By exploring Sedaris’ isolation, we can discover that socially constructed standards of normativity are at best arbitrary, and at worst violent.

As a young boy, Sedaris is initially completely unaware that his tics are not socially acceptable in the outside world. He is puzzled when his teacher, Miss Chestnut, correctly guesses that he is “going to hit [himself] over the head with [his] shoe” (361), despite the obvious removal of his shoe during their private meeting. Miss Chestnut continues by embarrassingly making fun out of the fact that Sedaris’ cannot help but “bathe her light switch with [his] germ-ridden tongue” (361) repeatedly throughout the school day. She targets Sedaris with mocking questions, putting him on the spot in front of his class; this behavior is not ethical due to Sedaris’ age. It violates the trust that students should have in their teachers and other caregivers. Miss Chestnut criticizes him excessively for his ambiguous, child-like answers. For example, she drills him on whether it is “healthy to hit ourselves over the head with our shoes” (361) and he “guess[es] that it was not,” (361) as a child might phrase it. She ridicules his use of the term “guess,” using obvious examples of instances when guessing would not be appropriate, such as “[running] into traffic with a paper sack over [her] head” (361). Her mockery is not only rude, but ableist and unethical. Any teacher—at least nowadays—should recognize that Sedaris needs compassion and support, not emotional abuse.

These kinds of negative responses to Sedaris’ behavior continue upon his return home, in which the role of the insensitive authority figure is taken on by his mother. In a time when maternal support is crucial for a secure and confident upbringing, Sedaris’ mother was never understanding of his behavior, and left little room for open, honest discussion regarding ways to cope with his compulsiveness. She reacted harshly to the letter sent home by Miss Chestnut, nailing Sedaris, exclaiming that his “goddamned math teacher” (363) noticed his strange behaviors, as if it should have been obvious to young, egocentric Sedaris. When teachers like Miss Chestnut meet with her to discuss young David’s problems, she makes fun of him, imitating his compulsions; Sedaris is struck by “a sharp, stinging sense of recognition” upon viewing this mockery (365). Sedaris’ mother, too, is an authority figure who maintains ableist standards of normativity by taunting her own son. Meeting with teachers should be an opportunity to truly help David, not tease him.

On the day that Miss Chestnut makes her appearance in the Sedaris household to discuss his behaviors with his mother, Sedaris watches them from the staircase, helplessly embarrassed. We can infer from this scene that Sedaris has actually become aware of that fact that his tics are not considered to be socially acceptable, and that he must be “the weird kid” among his peers—and even to his parents and teachers. His mother’s cavalier derision demonstrates her apparent disinterest in the well-being of he son, as she blatantly brushes off his strange behaviors except in the instance during which she can put them on display for the purpose of entertaining a crowd. What all of these pieces of his mother’s flawed personality show us is that she has issues too—drinking and smoking, in addition to her poor mothering—but yet Sedaris is the one being chastised while she lives a normal life. Later in the essay, Sedaris describes how “a blow to the nose can be positively narcotic” (366), drawing a parallel to his mother’s drinking and smoking. From this comparison, we can begin to see flawed standards of “normal behavior”: although many people drink and smoke (especially at the time the story takes place), these habits are much more harmful than what Sedaris does in private.

Sedaris’ father has an equally harmful personality, but it manifests differently. Sedaris describes him as a hoarder, one who has, “saved it all: every last Green Stamp and coupon, every outgrown bathing suit and scrap of linoleum” (365). Sedaris’ father attempts to “cure [Sedaris] with a series of threats” (366). In one scene, he even enacts violence upon David by slamming on the brakes of the car while David has his nose pressed against a windshield. Sedaris reminds us that his behavior might have been unusual, but it wasn’t violent: “So what if I wanted to touch my nose to the windshield? Who was I hurting?” (366). In fact, it is in that very scene that Sedaris draws the aforementioned parallel to his mother’s drinking: when Sedaris discovers that “a blow to the nose can be positively narcotic,” it is while his father is driving around “with a lapful of rejected, out-of-state coupons” (366). Not only is Sedaris’ father violating the trust David places in him as a caregiver; his hoarding is an arguably unhealthy habit that simply happens to be more socially acceptable than licking a concrete toadstool. Comparing Sedaris’s tics to his father’s issues, it is apparent that his father’s are much more harmful than his own. None of the adults in Sedaris’ life are innocent—“mother smokes and Miss Chestnut massaged her waist twenty, thirty times a day—and here I couldn’t press my nose against the windshield of a car” (366)—but nevertheless, Sedaris’s problems are ridiculed or ignored by the ‘normal’ people in his life, again bringing into question what it means to be a normal person.

In high school, Sedaris’ begins to take certain measures to actively control and hide his socially unacceptable behaviors. “For a time,” he says, “I thought that if I accompanied my habits with an outlandish wardrobe, I might be viewed as eccentric rather than just plain retarded” (369). Upon this notion, Sedaris starts to hang numerous medallions around his neck, reflecting that he “might as well have worn a cowbell” (369) due to the obvious noises they made when he would jerk his head violently, drawing more attention to his behaviors (the opposite of the desired effect). He also wore large glasses, which he now realizes made it easier to observe his habit of rolling his eyes into his head, and “clunky platform shoes [that] left lumps when used to discreetly tap [his] forehead” (369). Clearly Sedaris was trying to appear more normal, in a sense, but was failing terribly. After high school, Sedaris faces the new wrinkle of sharing a college dorm room. He conjures up elaborate excuses to hide specific tics, ensuring his roommate that “there’s a good chance the brain tumor will shrink” (369) if he shakes his head around hard enough and that specialists have ordered him to perform “eye exercises to strengthen what they call he ‘corneal fibers’” (369). He eventually comes to a point of such paranoid hypervigilance that he memorizes his roommate’s class schedule to find moments to carry out his tics in privacy. Sedaris worries himself sick attempting to approximate ‘normal’: “I got exactly fourteen minutes of sleep during my entire first year of college” (369). When people are pressured to perform an identity inconsistent with their own—pressured by socially constructed standards of normativity—they harm themselves in the process. Furthermore, even though the responsibility does not necessarily fall on Sedaris’ peers to offer support, we can assume that their condemnation of his behavior reinforces the standards that oppress him.

Sedaris’ compulsive habits peak and begin their slow decline when he picks up the new habit of smoking cigarettes, which is of course much more socially acceptable while just as compulsive in nature once addiction has the chance to take over. He reflects, from the standpoint of an adult, on the reason for the acquired habit, speculating that “maybe it was coincidental, or perhaps … much more socially acceptable than crying out in tiny voices” (371). He is calmed by smoking, saying that “everything’s fine as long I know there’s a cigarette in my immediate future” (372). (Remarkably, he also reveals that he has not truly been cured, as he revisits his former tics and will “dare to press [his] nose against the doorknob or roll his eyes to achieve that once-satisfying ache” [372.]) Sedaris has officially achieved the tiresome goal of appearing ‘normal’, as his compulsive tics seemed to “[fade] out by the time [he] took up with cigarettes” (371). It is important to realize, however, that Sedaris might have found a socially acceptable way to mask his tics, but not a healthy one. The fact that the only activity that could take place of his compulsive tendencies was the dangerous use of a highly addictive substance, one that has proven to be dangerously harmful with frequent and prolonged use, shows that he is conforming to the standards of society which do not correspond with healthy behaviors.

In a society full of dangerous, inconvenient, or downright strange habits that are nevertheless considered socially acceptable, David Sedaris suffered through the psychic and physical violence and negligence of those who should have cared for him. With what we can clearly recognize as a socially constructed disability, Sedaris was continually denied support and mocked by authority figures. He struggled to socialize and perform academically while still carrying out each task he was innately compelled to do, and faced consistent social hardship because of his outlandish appearance and behaviors that are viewed in our society as “weird.” Because of ableist, socially constructed standards of normativity, Sedaris had to face a long string of turmoil and worry that most of society may never come to completely understand. We can only hope that as a greater society, we continue sharing and studying stories like Sedaris’ so that we critique the flawed guidelines we force upon different bodies and minds, and attempt to be more accepting and welcoming of the idiosyncrasies we might deem to be unfavorable.

Teacher Takeaways

“The student clearly states their thesis in the beginning, threading it through the essay, and further developing it through a synthesized conclusion. The student’s ideas build logically through the essay via effective quote integration: the student sets up the quote, presents it clearly, and then responds to the quote with thorough analysis that links it back to their primary claims. At times this thread is a bit difficult to follow; as one example, when the student talks about the text’s American songs, it’s not clear how Rodriguez’s text illuminates the student’s thesis. Nor is it clear why the student believes Rodriguez is saying the “American Dream is not worth the love and emotion.” Without this clarification, it’s difficult to follow some of the connections the student relies on for their thesis, so at times it seems like they may be stretching their interpretation beyond what the text supplies.”– Professor Dannemiller

“I like how this student follows their thesis through the text, highlighting specific instances from Sedaris’s essay that support their analysis. Each instance of this evidence is synthesized with the student’s observations and connected back to their thesis statement, allowing for the essay to capitalize on the case being built in their conclusion. At the ends of some earlier paragraphs, some of this ‘spine-building’ is interrupted with suggestions of how characters in the essay should behave, which doesn’t always clearly link to the thesis’s goals. Similarly, some information isn’t given a context to help us understand its relevance, such as what violating the student-teacher trust has to do with normativity being a social construct, or how Sedaris’s description of ‘a blow to the nose’ being a narcotic creates a parallel to his mother’s drinking and smoking. Without further analysis and synthesis of this information the reader is left to guess how these ideas connect.”– Professor Dannemiller

Sedaris, David. “A Plague of Tics.” 50 Essays: A Portable Anthology , 4 th edition, edited by Samuel Cohen, Bedford, 2013, pp. 359-372.

Analyzing “Richard Cory” 10

In the poem “Richard Cory” by Edward Arlington Robinson, a narrative is told about the character Richard Cory by those who admired him. In the last stanza, the narrator, who uses the pronoun “we,” tells us that Richard Cory commits suicide. Throughout most of the poem, though, Cory had been described as a wealthy gentleman. The “people on the pavement” (2), the speakers of the poem, admired him because he presented himself well, was educated, and was wealthy. The poem presents the idea that, even though Cory seemed to have everything going for him, being wealthy does not guarantee happiness or health.

Throughout the first three stanzas Cory is described in a positive light, which makes it seem like he has everything that he could ever need. Specifically, the speaker compares Cory directly and indirectly to royalty because of his wealth and his physical appearance: “He was a gentleman from sole to crown, / Clean favored and imperially slim” (Robinson 3-4). In line 3, the speaker is punning on “soul” and “crown.” At the same time, Cory is both a gentleman from foot (sole) to head (crown) and also soul to crown. The use of the word “crown” instead of head is a clever way to show that Richard was thought of as a king to the community. The phrase “imperially slim” can also be associated with royalty because imperial comes from “empire.” The descriptions used gave clear insight that he was admired for his appearance and manners, like a king or emperor.

In other parts of the poem, we see that Cory is ‘above’ the speakers. The first lines, “When Richard Cory went down town, / We people on the pavement looked at him” (1-2), show that Cory is not from the same place as the speakers. The words “down” and “pavement” also suggest a difference in status between Cory and the people. The phrase “We people on the pavement” used in the first stanza (Robinson 2), tells us that the narrator and those that they are including in their “we” may be homeless and sleeping on the pavement; at the least, this phrase shows that “we” are below Cory.

In addition to being ‘above,’ Cory is also isolated from the speakers. In the second stanza, we can see that there was little interaction between Cory and the people on the pavement: “And he was always human when he talked; / But still fluttered pulses when he said, / ‘Good- morning’” (Robinson 6-8). Because people are “still fluttered” by so little, we can speculate that it was special for them to talk to Cory. But these interactions gave those on the pavement no insight into Richard’s real feelings or personality. Directly after the descriptions of the impersonal interactions, the narrator mentions that “he was rich—yes, richer than a king” (Robinson 9). At the same time that Cory is again compared to royalty, this line reveals that people were focused on his wealth and outward appearance, not his personal life or wellbeing.

The use of the first-person plural narration to describe Cory gives the reader the impression that everyone in Cory’s presence longed to have the life that he did. Using “we,” the narrator speaks for many people at once. From the end of the third stanza to the end of the poem, the writing turns from admirable description of Richard to a noticeably more melancholy, dreary description of what those who admired Richard had to do because they did not have all that Richard did. These people had nothing, but they thought that he was everything. To make us wish that we were in his place. So on we worked, and waited for the light,

And went without the meat, and cursed the bread…. (Robinson 9-12)

They sacrificed their personal lives and food to try to rise up to Cory’s level. They longed to not be required to struggle. A heavy focus on money and materialistic things blocked their ability to see what Richard Cory was actually feeling or going through. I suggest that “we” also includes the reader of the poem. If we read the poem this way, “Richard Cory” critiques the way we glorify wealthy people’s lives to the point that we hurt ourselves. Our society values financial success over mental health and believes in a false narrative about social mobility.

Though the piece was written more than a century ago, the perceived message has not been lost. Money and materialistic things do not create happiness, only admiration and alienation from those around you. Therefore, we should not sacrifice our own happiness and leisure for a lifestyle that might not make us happy. The poem’s message speaks to our modern society, too, because it shows a stigma surrounding mental health: if people have “everything / To make us wish that we were in [their] place” (11-12), we often assume that they don’t deal with the same mental health struggles as everyone. “Richard Cory” reminds us that we should take care of each other, not assume that people are okay because they put up a good front.

“I enjoy how this author uses evidence: they use a signal phrase (front-load) before each direct quote and take plenty of time to unpack the quote afterward. This author also has a clear and direct thesis statement which anticipates the content of their analysis. I would advise them, though, to revise that thesis by ‘previewing’ the elements of the text they plan to analyze. This could help them clarify their organization, since a thesis should be a road-map.”– Professor Wilhjelm

Robinson, Edward Arlington. “Richard Cory.” The Norton Introduction to Literature , Shorter 12 th edition, edited by Kelly J. Mays, Norton, 2017, p. 482.

the cognitive process and/or rhetorical mode of studying constituent parts to demonstrate an interpretation of a larger whole.

a part or combination of parts that lends support or proof to an arguable topic, idea, or interpretation.

a cognitive and rhetorical process by which an author brings together parts of a larger whole to create a unique new product. Examples of synthesis might include an analytical essay, found poetry, or a mashup/remix.

a 1-3 sentence statement outlining the main insight(s), argument(s), or concern(s) of an essay; not necessary in every rhetorical situation; typically found at the beginning of an essay, though sometimes embedded later in the paper. Also referred to as a “So what?” statement.

EmpoWORD: A Student-Centered Anthology and Handbook for College Writers Copyright © 2018 by Shane Abrams is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

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Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design (2020)

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4 Literature Review and Synthesis Literature Review Purpose of Literature Review Performance-based seismic design (PBSD) for infrastructure in the United States is a developing field, with new research, design, and repair technologies; definitions; and method- ologies being advanced every year. A synthesis report, NCHRP Synthesis 440: Performance- Based Seismic Bridge Design (Marsh and Stringer 2013), was created to capture PBSD understanding up to that point. This synthesis report described the background, objec- tives, and research up until 2011 to 2012 and synthesized the information, including areas where knowledge gaps existed. The literature review in this research report focuses on new infor mation developed after the efforts of NCHRP Synthesis 440. The intention is that this research report will fuel the next challenge: developing a methodology to implement PBSD for bridge design. Literature Review Process Marsh and Stringer (2013) performed an in-depth bridge practice review by sending a questionnaire to all 50 states, with particular attention to regions with higher seismic hazards. The survey received responses from a majority of those agencies. This process was continued in the current project with a request for new information or research that the state depart- ment of transportation (DOT) offices have participated in or are aware of through other organizations. The research team reached out to the list of states and researchers in Table 1. An X within a box is placed in front of their names if they responded. The team also examined the websites of the state DOTs that participated to investigate whether something was studied locally, especially work being developed in California. The research team made an additional effort to perform a practice review of bridge designs, research, and other design industries, specifically in the building industry. The building industry has been developing PBSD for more than 20 years, and some of their developments are appli- cable to bridge design. These combined efforts have allowed the research team to assemble an overview of the state of PBSD engineering details and deployment since Marsh and Stringer’s (2013) report was published. NCHRP Synthesis 440 primarily dealt with the effects of strong ground motion shaking. Secondary effects such as tsunami/seiche, ground failure (surface rupture, liquefaction, or slope failure), fire, and flood were outside the scope of this study. Regardless, their impact on bridges may be substantial, and investigation into their effects is undoubtedly important. C H A P T E R 2

Literature Review and Synthesis 5 The following e-mail was sent to the owners and researchers. Dear (individual): We are assisting Modjeski & Masters with the development of proposed guidelines for Performance- Based Seismic Bridge Design, as part of NCHRP [Project] 12-106. Lee Marsh and our Team at BergerABAM are continuing our efforts from NCHRP Synthesis 440, which included a literature review up to December of 2011. From this timeframe forward, we are looking for published research, contractual language, or owner documents that deal with the following categories: 1. Seismic Hazards (seismic hazard levels, hazard curves, return periods, geo-mean vs. maximum direc- tion, probabilistic vs. deterministic ground motions, conditional mean spectrum, etc.) 2. Structure Response (engineering design parameters, materials and novel columns, isolation bearings, modeling techniques, etc.) 3. Damage Limit States (performance descriptions, displacement ductility, drift ratios, strain limits, rotation curvature, etc.) 4. Potential for Loss (damage descriptions, repairs, risk of collapse, economical loss, serviceability loss, etc.) 5. Performance Design Techniques (relating hazard to design to performance to risk, and how to assess [these] levels together) If you are aware of this type of resource, please provide a contact that we can work with to get this information or provide a published reference we can gather. Your assistance is appreciated. We want to minimize your time, and ask that you respond by Wednesday, 8 February 2017. Thank you again, Research Team Synthesis of PBSD (2012–2016) Objectives of NCHRP Synthesis 440 The synthesis gathered data from a number of different but related areas. Marsh and Stringer (2013), herein referred to as NCHRP Synthesis 440, set the basis for this effort. The research report outline follows what has been added to the NCHRP Synthesis 440 effort since 2012. The information gathered that supplements NCHRP Synthesis 440 includes, but is not limited to, the following topics. • Public and engineering expectations of seismic design and the associated regulatory framework Participation State Alaska DOT Arkansas DOT California DOT (Caltrans) Illinois DOT Indiana DOT Missouri DOT Montana DOT Nevada DOT Oregon DOT South Carolina DOT Utah DOT Washington State DOT Table 1. List of state DOT offices and their participation.

6 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design • Seismic hazard analysis • Structural analysis and design • Damage analysis • Loss analysis • Organization-specific criteria for bridges • Project-specific criteria Where new or updated information is available for these areas, a summary is included. Marsh and Stringer (2013) also identified gaps in the knowledge base of PBSD, current as of 2012, that need to be closed. Knowledge gaps certainly exist in all facets of PBSD; however, key knowledge gaps that should be closed in order to implement PBSD are covered. • Gaps related to seismic hazard prediction • Gaps related to structural analysis • Gaps related to damage prediction • Gaps related to performance • Gaps related to loss prediction • Gaps related to regulatory oversight and training • Gaps related to decision making These knowledge gaps have been filled in somewhat in this research report but, for the most part, these areas are still the key concepts that require additional development to further the development of a PBSD guide specification. Public and Engineering Expectations of Seismic Design and the Associated Regulatory Framework The public expectation of a structure, including a bridge, is that it will withstand an earthquake, but there is a limited understanding of what that actually means. Decision makers struggle to understand how a bridge meeting the current requirements of the AASHTO Guide Specifications for LRFD Seismic Bridge Design (2011), herein referred to as AASHTO guide specifications, will perform after either the expected (design) or a higher level earthquake. Decision makers understand the basis of life safety, wherein the expectation is that no one will perish from a structure collapsing, but often mistakenly believe that the structure will also be usable after the event. In higher level earthquakes, even in some lower level events, this is not true without repair, retrofit, or replacement. In the past decade, there has been an increased awareness by owners and decision makers as to the basis of seismic design. As a result, a need has developed for performance criteria so that economic and social impacts can be interwoven with seismic design into the decision processes (see Figure 1). Several states, including California, Oregon, and the State of Washington, are working toward resiliency plans, although these are developed under different titles or programs within the states. Resiliency has been defined in several ways: (1) amount of damage from an event measured in fatalities, structural replacement cost, and recovery time and (2) the time to resto- ration of lifelines, reoccupation of homes and structures, and, in the short term, resumption of normal living routines. The California DOT Caltrans has generated risk models and is in the process of developing a new seismic design specification to address PBSD in bridge design. The risk models and specifications are not published yet, but the use in PBSD is discussed in greater detail later in this chapter.

Literature Review and Synthesis 7 The State of Washington The State of Washington’s resiliency plan, outlined in Washington State Emergency Management Council–Seismic Safety Committee (2012), works to identify actions and policies before, during, and after an earthquake event that can leverage existing policies, plans, and initiatives to realize disaster resilience within a 50-year life cycle. The hazard level used for trans- portation planning is the 1000 year event. The goals for transportation systems vary depending on the type of service a route provides, as shown in following components of the plan. For major corridors such as Interstates 5, 90, and 405 and floating bridges SR 520, I-90, and Hood Canal, the target timeframe for response and recovery is between 1 to 3 days and 1 to 3 months, depending on location. The current anticipated timeframe based on current capacity and without modifications is between 3 months to 1 year and 1 to 3 years, depending on location. The actual response and recovery time will depend on a number of factors. For example: 1. The number of Washington State DOT personnel who are able to report to work may be limited by a variety of circumstances, including where personnel were at the time of the earthquake and whether they sustained injuries. 2. Bridges and roadways in earthquake-affected areas must be inspected. How long this takes will depend on the number and accessibility of the structures and the availability of qualified inspectors. 3. Some bridges and segments of road may be rendered unusable or only partially usable as a result of the earthquake or secondary effects. The response and recovery timeframe will depend on the number, the location, and the extent of the damage. 4. Certain earthquake scenarios could result in damage to the Ballard Locks and cause the water level in Lake Washington to drop below the level required to operate the floating bridges. 5. Depending on the scenario and local conditions, liquefaction and slope failure could damage both interstates and planned detours. During the first 3 days after the event, the Washington State Department of Transportation (Washington State DOT) will inspect bridges and begin repairs as needed. Washington State DOT’s first priority will be to open key routes for emergency response vehicles. Subsequent phases of recovery will include setting up detours where necessary and regulating the type and Figure 1. PBSD decision-making process (Guidelines Figure 2.0-1). References to guidelines figures and tables within parentheses indicate the proposed AASHTO guidelines.

8 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design volume of traffic, to give the public as much access as possible while damaged roads and bridges are repaired. For major and minor arterials, which encompass arterial roadways (including bridges) other than the interstates (so therefore includes state highways and many city and county roads), the target timeframe for response and recovery is between 0 to 24 hours and 3 months to 1 year, depending on location; the percentage of roadways that are open for use will increase over this period. Anticipated timeframe based on current capacity is between 1 week to 1 month and 1 to 3 years, depending on location; the percentage of roadways that are open for use will increase over this period. The goal of Washington State Emergency Management Council’s resiliency plan is to establish a means to coordinate agencies, public–private partnerships, and standards toward these resiliency goals. The plan outlines goals for recovery times for transportation systems in terms of hours, days, weeks, months, and years, with targets to achieve different levels of recovery (see Table 2) as follows. Similar recovery timeframe processes were established for service sectors (e.g., hospitals, law enforcement, and education); utilities; ferries, airports, ports, and navigable waterways; mass transit; and housing. The overall resiliency plan also discusses the degree to which the recovery of one component or sector would depend on the restoration of another. The key interdependencies that the participants identified include information and communication technologies, transportation, electricity, fuel, domestic water supplies, wastewater systems, finance and banking, and planning and community development. It appears that the implementation of the Washington State Emergency Management Council’s initiative, originally assumed to take 2.5 to 3 years in 2012, has not seen significant development since then. However, the State’s initiative to develop a more resilient community has been extended down to the county level, with King County’s efforts referenced in Rahman et al. (2014) and, at the city level, with the City of Seattle referenced in CEMP (2015). This reflects the commitment needed not only by the legislature and the state departments but also by other agencies (e.g., county, city, or utilities) and the public to take an interest in, and provide funding for, the development of a resiliency plan. The recovery continuum is presented graphically in Figure 2. Developing this relationship with other agency plans is an iterative process that will take time, as shown in Figure 3. Identifying the critical sectors of the agency is necessary to develop a resiliency model and determine how to approach a disaster recovery framework. King County worked from Washington State’s initiative to develop Figure 4. The Oregon DOT Oregon DOT has developed a variation of the approach identified by the State of Wash- ington; further discussion is found later in this chapter. Other Resilience Documents The building industry has recently seen the development of two additional documents that address PBSD in terms of expectations and process. The REDi Rating System from REDi (2013) sets an example for incorporating resilience- based design into the PBSD process. This document outlines structural resilience objectives for organizational resilience, building resilience, loss assessment, and ambient resilience to evaluate and rate the decision making and design methodology using PBSD for a specific project.

Literature Review and Synthesis 9 The document is one of the only references that addresses a system to develop probabilistic methods to estimate downtime. The overall intent is to provide a roadmap to resilience. This roadmap is intended to allow owners to resume business operation and to provide livable conditions quickly after an earthquake. The Los Angeles Tall Buildings Structural Design Council (LATBSDC 2014) created an alter- native procedure specific to their location. Design specification criteria are identified and modi- fications are described as appropriate for the PBSD approach to tall buildings in this localized Minimal (A minimum level of service is restored, primarily for the use of emergency responders, repair crews, and vehicles transporting food and other critical supplies.) Functional (Although service is not yet restored to full capacity, it is sufficient to get the economy moving again—for example, some truck/freight traffic can be accommodated. There may be fewer lanes in use, some weight restrictions, and lower speed limits.) Operational (Restoration is up to 80 to 90 percent of capacity: A full level of service has been restored and is sufficient to allow people to commute to school and to work.) Time needed for recovery to 80 to 90 percent operational given current conditions. Source: Washington State Emergency Management Council–Seismic Safety Committee (2012). Table 2. Washington State’s targets of recovery.

10 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Source: Adapted from FHWA by CEMP (2015). Figure 2. Recovery continuum process. Source: CEMP (2015). Figure 3. Relationship of disaster recovery framework to other city plans. region. This procedure is a good example of how PBSD criteria and methodology need to be established locally, with a knowledge of risk, resources, and performance needs in order to set the criteria for true PBSD. Seismic Hazard Prediction As outlined in NCHRP Synthesis 440, the seismic hazard includes the regional tectonics and the local site characteristics from either a deterministic or probabilistic viewpoint. The deterministic form allows the assessment of shaking at a site as a function of the controlling earthquake that can occur on all the identified faults or sources. The probabilistic approach

Literature Review and Synthesis 11 defines an acceleration used in design that would be exceeded during a given window of time (e.g., a 7% chance of exceedance in 75 years). The following subsections provide a summary of procedures currently used within AASHTO, as well as new issues that should be eventually addressed in light of approaches used by the building industry. AASHTO Probabilistic Approach As summarized in the AASHTO guide specifications, the current approach used by AASHTO involves the use of a probabilistic hazard model with a nominal return period of 1000 years. Baker (2013) noted that the probabilistic seismic hazard analysis involves the following five steps: 1. Identify all earthquake sources capable of producing damaging ground motions. 2. Characterize the distribution of earthquake magnitudes (the rates at which earthquakes of various magnitudes are expected to occur). 3. Characterize the distribution of source-to-site distances associated with potential earthquakes. 4. Predict the resulting distribution of ground motion intensity as a function of earthquake magnitude, distance, and so forth. 5. Combine uncertainties in earthquake size, location, and ground motion intensity, using a calculation known as the total probability theorem. While implementation of the five steps in the probabilistic approach is beyond what most practicing bridge engineers can easily perform, AASHTO, working through the U.S. Geological Survey, developed a website hazard tool that allows implementation of the probabilistic proce- dure based on the latitude and longitude of a bridge site. The product of the website includes peak ground acceleration (PGA), spectral acceleration at 0.2 s (Ss), and spectral acceleration at 1 s (S1). These values are for a reference-site condition comprising soft rock/stiff soil, having a time-averaged shear wave velocity (Vs) over the upper 100 feet of soil profile equal to 2500 feet per second (fps). The Geological Survey website can also correct for local site conditions following procedures in the AASHTO Guide Specifications for LRFD Seismic Bridge Design. One of the limitations of the current U.S. Geological Survey hazard website is that it is based on a seismic hazard model developed in 2002. The Geological Survey updated its seismic model in 2008 and then in 2014; however, these updates are currently not implemented within the AASHTO hazard model on the Geological Survey’s website. Oregon and the State of Washington have updated the seismic hazard map used by the Oregon DOT and the Washington State Source: Rahman et al. (2014). Figure 4. Resilient King County critical sectors and corresponding subsectors.

12 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design DOT to include the 2014 U.S. Geological Survey hazard model; however, most state DOTs are still using the out-of-date hazard model. Use of the outdated hazard model introduces some inconsistencies in ground motion prediction, relative to the current Geological Survey hazard website tool at some locations. Discussions are ongoing between NCHRP and the U.S. Geological Survey to update the 2002 website tool. Another issue associated with the current AASHTO probabilistic method is that it is based on the geomean of the ground motion. In other words, the ground motion prediction equations in the hazard model are based on the geomean of recorded earthquake motions. These motions are not necessarily the largest motion. The building industry recognized that the maximum direction could result in larger ground motions and introduced maximum direction corrections. These corrections increase spectral acceleration by a factor of 1.1 and S1 by a factor of 1.3. The relevance of this correction to bridges is discussed in the next subsection of this review. The building industry also introduced a risk-of-collapse correction to the hazard model results. This correction is made to Ss and S1. The size of the correction varies from approximately 0.8 to 1.2 within the continental United States. It theoretically adjusts the hazard curves to provide a 1% risk of collapse in 50 years. The risk-of-collapse corrections were developed by the U.S. Geological Survey for a range of building structures located throughout the United States. Although no similar corrections have been developed for bridges, the rationale for the adjust- ment needs to be further evaluated to determine if the rationale should be applied to bridge structures. As a final point within this discussion of probabilistic methods within the AASHTO guide specifications, there are several other areas of seismic response that need to be considered. These include near-fault and basin effects on ground motions, as well as a long-period transition factor. The near-fault and basin adjustments correct the Ss and S1 spectral accelerations for locations near active faults and at the edge of basins, respectively. These adjustments typically increase spectral accelerations at longer periods (> 1 s) by 10% to 20%, depending on specifics of the site. The long-period transition identifies the point at which response spectral ordinates are no longer proportional to the 1/T decay with increasing period. These near-fault, basin, and long-period adjustments have been quantified within the building industry guidance documents but remain, for the most part, undefined within the AASHTO guide specifications. As bridge discussions and research move closer to true probabilistic format for PBSD, these issues need to be addressed as part of a future implementation process. Correction for Maximum Direction of Motion Over the last decade, a debate has been under way within the building industry regarding the appropriate definition of design response spectra (Stewart et al. 2011). The essence of the argument relates to the representation of bidirectional motion via response spectra. In both the AASHTO LRFD Bridge Design Specifications (2014), as well as the AASHTO Guide Specifications for LRFD Seismic Bridge Design (SGS), response spectra are established by defining spectral ordinates at two or three different periods from design maps developed by the U.S. Geological Survey for a return period of 1000 years. The resulting spectra are then adjusted for local site conditions, resulting in the final design spectra. In establishing the design maps for parameters such as Ss and S1, the U.S. Geological Survey has traditionally relied upon probabilistic seismic hazard analysis, which utilizes ground motion prediction equations (GMPEs) defined by the geometric mean of the two principal directions of recorded motion. In 2006, Boore introduced a new rotation independent geometric mean definition termed GMRotI50 (Boore et al. 2006). Then, in 2010, Boore developed a new defini- tion that does not rely upon the geometric mean termed RotD50 spectra, which can be generi- cally expressed as RotDNN spectra, where NN represents the percentile of response (i.e., 50 is

Literature Review and Synthesis 13 consistent with the median, 0 is the minimum, and 100 is the maximum). The NGA–West2 project GMPEs utilized RotD50 spectra for the ground motion models; however, the 2009 National Earthquake Hazards Reduction Program (NEHRP) provisions adopted a factor to modify the median response, RotD50, to the maximum possible response, RotD100 as the spectra for the design maps (Stewart et al. 2011). Introducing RotD100 resulted in a 10% to 30% increase in spectral ordinates results relative to the geometric mean, which has traditionally been used as a basis of seismic design. In order to appreciate the impact of these choices, a brief discussion of RotDNN spectra is warranted. As described in Boore (2010), for a given recording station, the two orthogonal- component time series are combined into a single time series corresponding to different rotation angles, as shown in Equation 1: aROT(t ; θ) = a1(t)cos(θ) + a2(t)sin(θ) (1) where a1(t ) and a2(t ) are the orthogonal horizontal component acceleration time series and θ is the rotation angle. For example, consider the two orthogonal horizontal component time series, H1 and H2, shown in Figure 5. The single time series corresponding to the rotation angle θ is created by combining the Direction 1 and Direction 2 time series. Then, the response spectrum for that single time series can be obtained, as shown in the figure. The process is repeated for a range of azimuths from 0° to one rotation-angle increment less than 180°. If the rotation-angle increment is θ, then there will be 180/θ single time series, as well as 180/θ corresponding response spectra. For example, if θ = 30°, then there will be six single time series (the original two, as well as four generated time series), as well as six response spectra, as shown in Figure 6. Once the response spectra for all rotation angles are obtained, then the nth percentile of the spectral amplitude over all rotation angles for each period is computed (e.g., RotD50 is the median value and RotD100 is the largest value for all rotation angles). For example, at a given period of 1 s, the response spectra values for all rotation angles are sorted, and the RotD100 value would be the largest value from all rotation angles while RotD50 would be the median. This is repeated for all periods, with potentially different rotation angles, producing the largest Source: Palma (2019). Figure 5. Combination of time series to generate rotation dependent spectra.

14 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design response at any given period (period-dependent rotation angle.) Figure 7 shows an example of the two orthogonal horizontal components, as well as the RotD50 and RotD100 spectra for the as-recorded ground motion from the 2011 Christchurch, New Zealand, earthquake at Kaiapoi North School station. As can be seen in the sample spectra (see Figure 7), the RotD100 spectrum represents a sub- stantial increase in demand when compared with the RotD50 spectrum. The main question facing the bridge community from this point onward is the appropriate selection of response spectra definition. This question can only be answered by developing sample designs to both the RotD50 and RotD100 spectra, which would then be evaluated via no-linear time history analysis. Such a study will require multiple bridge configurations and multiple ground motions. As an example of the potential impact, Figure 8 shows the results of a single-degree-of- freedom bridge column designed according to both RotD50 and RotD100 spectra, along with the resulting nonlinear time history analysis. The column was designed using direct displacement- based design to achieve a target displacement of 45 cm. It is clear from the results in Figure 8d that the nonlinear response of the column designed to the RotD100 spectrum matches the target Source: Palma (2019). Figure 6. Example of time series rotations with an angle increment (p) of 30ç. Source: Palma (2019). Figure 7. Sample spectra for a recorded ground motion pair.

Literature Review and Synthesis 15 reasonably well, while designing to the RotD50 spectrum results in displacements that are much greater than expected. This is, of course, only one result of an axisymmetric system. In the future (and outside the scope of this project), a systematic study could be conducted for both single degree of freedom and multiple degrees of freedom systems. The literature on this topic can be divided into two categories: (1) response spectra definitions and (2) impact on seismic response. The majority of the literature addresses the former. For example, Boore et al. (2006) and Boore (2010) introduced orientation-independent measures of seismic intensity from two horizontal ground motions. Boore et al. (2006) proposed two measures of the geometric mean of the seismic intensity, which are independent of the in-situ orientations of the sensors. One measure uses period-dependent rotation angles to quantify the spectral intensity, denoted GMRotDnn. The other measure is the GMRotInn, where I stands for period-independent. The ground motion prediction equations of Abrahamson and Silva (1997), Figure 8. Single bridge column designed according to both RotD50 and RotD100 spectra (Tabas EQ = Tabas earthquake and displ. = displacement).

16 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Boore et al. (1997), Campbell and Bozorgnia (2003), and Sadigh et al. (1997) have been updated using GMRotI50 as the dependent variable. Since more users within the building industry expressed the desire to use the maximum spec- tral response over all the rotation angles without geometric means, Boore (2010) introduced the measures of ground-shaking intensity irrespective of the sensor orientation. The measures are RotDnn and RotInn, whose computation is similar to GMRotDnn and GMRotInn without computing the geometric means. With regard to impact on seismic response, the opinion paper by Stewart et al. (2011) and the work by Mackie et al. (2011) on the impact of incidence angle on bridge response are relevant. Specifically, Stewart et al. (2011) noted the importance of computational analysis of structures (which had not been done as of 2011) in proposing appropriate spectra definitions. Other Methodologies for Addressing Seismic Ground Motion Hazards There are several other reports that address the question of the methodology that may be utilized in developing the seismic hazard. These recent studies endeavored to create a method- ology that is easier for engineers, as users, to understand how to tie the seismic hazard to the performance expectation. The variability of these approaches also demonstrates the broad range of options and therefore a limited understanding by practitioners in the bridge design industry. Following are some examples that apply to PBSD. Wang et al. (2016) performed a probabilistic seismic risk analysis (SRA) based on a single ground motion parameter (GMP). For structures whose responses can be better predicted using multiple GMPs, a vector-valued SRA (VSRA) gives accurate estimates of risk. A simplified approach to VSRA, which can substantially improve computational efficiency without losing accuracy, and a new seismic hazard de-aggregation procedure are proposed. This approach and the new seismic hazard de-aggregation procedure would allow an engineer to determine a set of controlling earthquakes in terms of magnitude, source–site distance, and occurrence rate for the site of interest. Wang et al. presented two numerical examples to validate the effectiveness and accuracy of the simplified approach. Factors affecting the approximations in the simplified approach were discussed. Kwong and Chopra (2015) investigated the issue of selecting and scaling ground motions as input excitations for response history analyses of buildings in performance-based earthquake engineering. Many ground motion selection and modification procedures have been developed to select ground motions for a variety of objectives. This report focuses on the selection and scaling of single, horizontal components of ground motion for estimating seismic demand hazard curves of multistory frames at a given site. Worden et al. (2012) used a database of approximately 200,000 modified Mercalli intensity (MMI) observations of California earthquakes collected from U.S. Geological Survey reports, along with a comparable number of peak ground motion amplitudes from California seismic networks, to develop probabilistic relationships between MMI and peak ground velocity (PGV), PGA, and 0.3-s, 1-s, and 3-s 5% damped pseudo-spectral acceleration. After associating each ground motion observation with an MMI computed from all the seismic responses within 2 kilometers of the observation, a joint probability distribution between MMI and ground motion was derived. A reversible relationship was then derived between MMI and each ground motion parameter by using a total least squares regression to fit a bilinear function to the median of the stacked probability distributions. Among the relationships, the fit-to-peak ground velocity has the smallest errors, although linear combinations of PGA and PGV give nominally better results. The magnitude and distance terms also reduce the overall residuals and are justifiable on an information theoretical basis.

Literature Review and Synthesis 17 Another approach to developing the appropriate seismic hazard comes out of Europe. Delavaud et al. (2012) presented a strategy to build a logic tree for ground motion prediction in European countries. Ground motion prediction equations and weights have been determined so that the logic tree captures epistemic uncertainty in ground motion prediction for six different tectonic regions in Europe. This includes selecting candidate GMPEs and simultaneously running them through a panel of six experts to generate independent logic trees and rank the GMPEs on available test data. The collaboration of this information is used to set a weight to the GMPEs and create a consensus logic tree. This output then is run through a sensitivity analysis of the proposed weights on the seismic hazard before setting a final logic tree for the GMPEs. Tehrani and Mitchell (2014) used updated seismic hazard maps for Montreal, Canada to develop a uniform hazard spectra for Site Class C and a seismic hazard curve to analyze bridges in the localized area. Kramer and Greenfield (2016) evaluated three case studies following the 2011 Tohoku earthquake to better understand and design for liquefaction. Existing case history databases are incomplete with respect to many conditions for which geotechnical engineers are often required to evaluate liquefaction potential. These include liquefaction at depth, liquefaction of relatively dense soils, and liquefaction of gravelly soils. Kramer and Greenfield’s investigation of the three case histories will add to the sparse existing data for those conditions, and their interpretations will aid in the validation and development of predictive procedures for liquefaction potential evaluation. Structural Analysis and Design Predicting the structural response to the earthquake ground motions is critical for the PBSD process. NCHRP Synthesis 440 outlined several analysis methods that can be used to accomplish this task. The multimodal linear dynamic procedures are outlined in AASHTO LRFD Bridge Design Specifications (AASHTO 2014) and AASHTO Guide Specifications for LRFD Seismic Bridge Design (AASHTO 2011), although the Guide Specifications also include the parameters for performing a model pushover analysis in addition to prescriptive detail practices to ensure energy-dissipating systems behave as intended and other elements are capacity-protected. Other methods of analysis may be better suited for PBSD, but the initial PBSD approach will likely follow the procedures of the AASHTO guide specifications, with multi-level hazards and performance expectations. Limited research and code development have been accomplished since NCHRP Synthesis 440, but one new analysis method, outlined in Babazadeh et al. (2015), includes a three-dimensional finite element model simulation that is used to efficiently predict intermediate damage limit states in a consistent manner, with the experimental observations extracted from the actual tested columns. Other recent articles of structural analysis identified areas of improvement in the current design methodology that may be beneficial to PBSD. Huff and Pezeshk (2016) compared the substitute structure method methodology for isolated bearings with the displacement-based design methodology for ordinary bridges and showed that these two methodologies vary in estimating inelastic displacements. Huff (2016a) identified issues that are generally simplified or ignored in current practice of predicting inelastic behavior of bridges during earthquakes, both on the capacity (in the section of the element type and geometric nonlinearities) and demand (issues related to viscous dampening levels) sides of the process. The current SGS methodology for nonlinear static procedures were compared in Hajihashemi et al. (2017) with recent methodologies for multimodal pushover procedures that take into account all significant modes of the structure and with modified equivalent linearization procedures developed for

18 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design FEMA-440 (FEMA 2005). All of these analysis articles identify areas of current discussion on how to improve the analytical procedures proposed in the SGS. NCHRP Synthesis 440 focused primarily on new analysis methods, but a recent increased focus, in both academia and industry, has to do with new materials and systems and their impacts on PBSD. The evolution of enhanced seismic performance has been wrapped into several research topics, such as accelerated bridge construction (ABC), novel columns, and PBSD. The following are several aspects, though not all-encompassing, which have been improved upon in the last 6 years or so. Improving Structural Analysis Through Better Material Data The analysis and performance of a bridge are controlled with material property parameters incorporated into the seismic analysis models, specifically for the push-over analysis method. AASHTO Guide Specifications for LRFD Seismic Bridge Design (AASHTO 2011) specifies the strain limits to use for ASTM A706 (Grade 60) and ASTM A615 Grade 60 reinforcement. These strain limits come from Caltrans study of 1,100 mill certificates for ASTM A706 Grade 60 in the mid-1990s for projects in Caltrans bridge construction. The results were reported as elongation—not strain—at peak stress, so select bar pull tests were performed to correlate elongation to strain at peak stress. This was assumed to be a conservative approach, though it has recently been validated with a new ASTM A706 Grade 80 study at North Carolina State University by Overby et al. (2015a), which showed Caltrans numbers, by comparison, for Grade 60 are reasonable and conservative. Overby et al. (2015b) developed stress strain parameters for ASTM A706 Grade 80 reinforcing steel. Approximately 800 tests were conducted on bars ranging from #4 to #18 from multiple heats from three producing mills. Statistical results were presented for elastic modulus, yield strain and stress, strain-hardening strain, strain at maximum stress, and ultimate stress. Research is currently under way at North Carolina State University that aims to identify strain limit states, plastic hinge lengths, and equivalent viscous damping models for bridge columns constructed from A706 Grade 80 reinforcing steel. Work is also under way at the University of California, San Diego, on applications of Grade 80 rebar for capacity-protected members such as bridge cap beams. Design Using New Materials and Systems Structural analysis and design are fundamentally about structural response to the earthquake ground motion and the analysis methods used to develop this relationship. The complexity of the analysis depends on the geometry of the structure and elements and the extent of inelastic behavior. This is coupled with the damage, or performance criteria but has been broken out for the purposes of this report and NCHRP Synthesis 440. Next generation bridge columns, often referred to as novel columns, are improving as a tool for engineers to control both the structural analysis, as the make-up of the material changes the inelastic behavior, and the element performance of bridges in higher seismic hazards. The energy-dissipating benefits of low damage materials—such as ultrahigh-performance concrete (UHPC), engineered cementi- tious composites (ECC), and shape memory alloy, fiber-reinforced polymer (FRP) wraps and tubes, elastomeric bearings, and post-tensioned strands or bars—can be utilized by engineers to improve seismic performance and life-cycle costs after a significant seismic event. Recent (Saiidi et al. 2017) studies tested various combinations of these materials to determine if there are columns that can be built with these materials that are equivalent to, or better than, conventional reinforced concrete columns (in terms of cost, complexity, and construction duration) but that improve seismic performance, provide greater ductility, reduce damage, and accommodate a quicker recovery time and reduce loss in both the bridge and the economic environment.

Literature Review and Synthesis 19 Accelerated bridge construction is also a fast-developing field in bridge engineering, with draft guide specifications for design and construction currently being developed for adop- tion by AASHTO for AASHTO LRFD Bridge Design Specifications (AASHTO 2014). ABC has economic impacts that go beyond seismic engineering, but research is focusing on details and connections for accelerated construction in higher seismic regions, moving two research paths forward at the same time. Tazarv and Saiidi (2014) incorporated ABC research with novel column research to evaluate combined novel column materials that can be constructed quickly. The research focused on the performance of materials and how to incorporate them into practice. Key mechanical properties of reinforcing SMA were defined as follows: • Observed yield strength (fyo) is the stress at the initiation of nonlinearity on the first cycle of loading to the upper plateau. • Austenite modulus (k1) is the average slope between 15% to 70% of fyo. • Post yield stiffness (k2) is the average slope of curve between 2.5% and 3.5% of strain on the upper plateau of the first cycle of loading to 6% strain. • Austenite yield strength (fy) is the stress at the intersection of line passing through origin with slope of k1 and line passing through stress at 3% strain with slope of k2. • Lower plateau inflection strength (fi) is the stress at the inflection point of lower plateau during unloading from the first cycle to 6% strain. • Lower plateau stress factor, β = 1 – (fi/fy). • Residual strain (eres) is the tensile strain after one cycle to 6% and unloading to 1 ksi (7 MPa). • Recoverable super-elastic strain (er) is maximum strain with at least 90% strain recovery capacity. Using the ASTM standard for tensile testing, er ≤ 6%. • Martensite modulus (k3) is the slope of the curve between 8% to 9% strain, subsequent to one cycle of loading to 6% strain, unloading to 1 ksi (7 MPa) and reloading to the ultimate stress. • Secondary post-yield stiffness ratio, α = k3/k1. • Ultimate strain (eu) is strain at failure. A graphical representation is shown in Figure 9, and minimum and expected mechanical properties are listed in Table 3. Other researchers, such as at the University of Washington, are currently testing grouted bars using conventional grouts and finding that these development lengths can be reduced greatly. However, it is the force transfer of the grouted duct to the reinforcing outside the duct that may Figure 9. NiTi SE SMA nonlinear model.

20 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design require additional length to adequately develop the energy-dissipating or capacity-protecting system that was intended by the designer for performance of the bridge in a high seismic event. Tazarv and Saiidi (2014) identified other material properties such as UHPC and ECC, shown in Tables 4 and 5, respectively. Tazarv and Saiidi (2014) also addressed grouted splice sleeve couplers, self-consolidating concrete (SCC), and other connection types that could be used in ABC and novel column configurations, testing these materials in the laboratory to see if various combinations produced a logical system to be carried forward in research, design, and implementation. Trono et al. (2015) studied a rocking post-tensioned hybrid fiber-reinforced concrete (HyFRC) bridge column that was designed to limit damage and residual drifts and that was tested dynamically under earthquake excitation. The column utilized post-tensioned strands, HyFRC, and a combination of unbonded and headed longitudinal reinforcement. There have been two projects related to the field of novel columns and ABC through the National Cooperative Highway Research Program. One project was NCHRP Project 12-101, which resulted in NCHRP Report 864, 2 volumes (Saiidi et al. 2017), and the other project was NCHRP Project 12-105, which resulted in NCHRP Research Report 935 (Saiidi et al. 2020). NCHRP Project 12-101 identified three novel column systems—specifically, SMA and ECC, ECC and FRP, and hybrid rocking column using post-tensioned strands and fiber-reinforced Parameter Tensile Compressive,ExpectedbExpectedbMinimuma Table 3. Minimum expected reinforcing NiTi SE SMA mechanical properties. Properties Range Poisson’s Ratio 0.2 Creep Coefficient* 0.2 to 0.8 Total Shrinkage** *Depends on curing conditions and age of loading. up to 900x10-6 Equation Compressive Strength (f'UHPC) f'UHPC 20 to 30 ksi, (140 to 200 MPa) Coefficient of Thermal Expansion (5.5 to 8.5)x10 -6/°F, (10 to 15)x10-6/°C Specific Creep* (0.04 to 0.3)x10 -6/psi, (6 to 45)x10-6/MPa A time-dependent equation for UHPC strength is available. Tensile Cracking Strength (ft,UHPC) ft,UHPC = 6.7 (psi) f'UHPCEUHPC = 49000 (psi) 0.9 to 1.5 ksi, (6 to 10 MPa) Modulus of Elasticity (EUHPC) 6000 to 10000 ksi, (40 to 70 GPa) **Combination of drying shrinkage and autogenous shrinkage and depends on curing method. Table 4. UHPC mechanical properties.

Literature Review and Synthesis 21 polymer confinement—and compared them to a conventional reinforced column. The research and properties of the material are provided; incorporating laboratory tests and calibration, design examples are created to help engineers understand how to use these advanced materials in a linear elastic seismic demand model and to determine performance using a pushover analysis. It is worth noting that ductility requirements do not accurately capture the perfor- mance capabilities of these novel columns, and drift ratio limits are being used instead, similar to the building industry. NCHRP Project 12-101 also provided evaluation criteria that can be evaluated and incorporated by AASHTO into a guide specification or into AASHTO Guide Specifications for LRFD Seismic Bridge Design (AASHTO 2011) directly. NCHRP Project 12-105 synthesized research, design codes, specifications, and contract language throughout all 50 states and combined the knowledge base and lessons learned for ABC into proposed guide specifications for both design and construction. This work focused on connections, and most of that information is related to seismic performance of ABC elements and systems. Earthquake resisting elements (ERE) and earthquake resisting systems (ERS) are specifically identified, defined, and prescribed for performance in AASHTO guide specifica- tions (AASHTO 2011) but only implicitly applied in AASHTO LRFD Bridge Design Specifications (AASHTO 2014). Since NCHRP Project 12-105 is applicable to both of these design resources, ERE and ERS are discussed in terms of how to apply performance to the force-based seismic design practice of AASHTO LRFD Bridge Design Specifications (AASHTO 2014). The proposed guide specification language also identifies when performance of materials have to be incor- porated into the design, say in higher seismic hazards, and when it is acceptable to apply ABC connections and detailing practices with prescriptive design methodologies. As the industry’s understanding of performance increases, the engineering industry is accepting the benefits that come from a more user-defined engineering practice that is implemented by identifying material properties; evaluating hazards and soil and structural responses; and verifying performance through strain limits, damage limits states, moment curvature, displacements, and ductility. These tools and advancements in ABC and novel column designs, including other material property performance and analytical methodologies, are allowing PBSD to advance in other areas, such as hazard prediction, loss prediction, and the owner decision-making process. Feng et al. (2014a) studied the application of fiber-based analysis to predict the nonlinear response of reinforced concrete bridge columns. Specifically considered were predictions of overall force-deformation hysteretic response and strain gradients in plastic hinge regions. The authors also discussed the relative merits of force-based and displacement-based fiber elements and proposed a technique for prediction of nonlinear strain distribution based on the modified compression field theory. Fulmer et al. (2013) developed a new steel bridge system that is based upon ABC techniques that employ an external socket to connect a circular steel pier to a cap beam through the use of grout and shear studs. The resulting system develops a plastic hinge in the pipe away from the column-to-cap interface. An advantage of the design is ease of construction, as no field welding Properties Range Flexural Strength 1.5 to 4.5 ksi (10 to 30 MPa) Modulus of Elasticity 2600 to 5000 ksi (18 to 34 GPa) Ultimate Tensile Strain 1 to 8% Ultimate Tensile Strength 0.6 to 1.7 ksi (4 to 12 MPa) First Crack Strength 0.4 to 1.0 ksi (3 to 7 MPa) Compressive Strength 3 to 14 ksi (20 to 95 MPa) Table 5. ECC mechanical properties.

22 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design is required: the two assemblies are placed together and the annular space between the column and cap filled with grout. Figure 10 shows the details of this connection, and Figure 11 shows a test of the system. Another system being investigated is isolation bearings or dampening devices. Xie and Zhiang (2016) investigated the effectiveness and optimal design of protective devices for the seismic protection of highway bridges. Fragility functions are first derived by probabilistic seismic demand analysis, repair cost ratios are then derived using a performance-based methodol- ogy, and the associated component failure probability. Subsequently, the researchers tried to identify the optimal design parameters of protective devices for six design cases with various combinations of isolation bearings and fluid dampers and discussed the outcomes. Damage mitigation through isolation and energy dissipation devices is continually improving based on research, development, and implementation in the field. Recent events within the State of Washington, Alaska, and other state agencies have shown that the benefits of these tools can be compromised if the intended performance cannot be sustained for the 75-year design life of the structure. Mackie and Stojadinovic (2015) outlined performance criteria for fabrica- tion and construction that need to be administered properly, and engineers should consider the effects of moisture, salts, or other corrosive environmental conditions that can affect the performance of the isolation or energy-dissipating system. Another constraint with these systems can be the proprietary nature that occurs as a specific isolation or energy-dissipating system is utilized to develop a specific performance expectation that can only be accomplished with the prescribed system. This proprietary nature of these systems can create issues for certain funding sources that require equal bidding opportunities and the project expense that can accompany a proprietary system. To address this type of design constraint, Illinois DOT has been developing an earthquake-resisting system (ERS) to leverage the displacement capacity available at typical bearings in order to provide seismic protection to substructures of typical bridges. LaFave et al. (2013a) identified the effects and design parameters, Source: Fulmer et al. (2013). 5" 4 at 5" O.C. A A A-A Connection Details 45° UT 100% 3 8" 12 Studs Spaced Around Cross Section 30°Typ. 15° Offset Studs Inside Pipe from Cap Beam CL HSS16x0.500 Pipe 24x0.500 2'-0"2 14 " 4 at 5" O.C. 212"-34 "Ø Shear Studs 1'-11" Pipe Stud Detail Grout Provided By and Placed by NCSU Figure 10. Grouted shear stud bridge system.

Literature Review and Synthesis 23 such as fuse capacity, shear response, and sliding response, which can be used to account for more standard bearing configurations in seismic analysis, especially lower seismic hazard regions. A variation on the use of bearings in order to improve seismic performance of a pier wall configuration was outlined in Bignell et al. (2006). Historically, pinned, rocking, and sliding bearings have been used with interior pier walls and steel girder superstructures. These bearing configurations were compared with replacement elastomeric bearing configurations and details for structural analysis techniques, damage limit states, and structural fragility, and performance through probability distributions were utilized as a PBSD process for determining solutions to seismic isolation and enhanced seismic performance. The foundation conditions, pier wall effects, bearing type, and even embankment effects to structural performance were included in this evaluation. Another approach to enhanced performance is modifications to foundation elements or increased understanding and modeling of soil–structure interaction, specifically where lateral spread or liquefaction design conditions make conventional bridge design and elements imprac- tical. One example of this is the seismic design and performance of bridges constructed with rocking foundations, as evaluated in Antonellis and Panagiotou (2013). This type of rocking goes beyond the loss of contact area currently allowed in the guide specifications. The applica- tion of columns supported on rocking foundations accommodates large deformations, while there is far less damage, and can re-center after large earthquakes. Another approach is to tie a tolerable displacement of an individual deep foundation element to a movement that would cause adverse performance, excessive maintenance issues, or functionality problems with the bridge structure. Roberts et al. (2011) established a performance-based soil–structure–interaction design approach for drilled shafts. Chiou and Tsai (2014) evaluated displacement ductility of an in-ground hinging of a fixed head pile. Assessment formulas were developed for the displacement ductility capacity of a fixed-head pile in cohesion-less soils. The parameters in the formulas included the sectional over-strength ratio and curvature ductility capacity, as well as a modification factor for consider- ing soil nonlinearity. The modification factor is a function of the displacement ratio of the pile’s ultimate displacement to the effective soil yield displacement, which is constructed through a number of numerical pushover analyses. Source: Fulmer et al. (2013). Figure 11. Photograph of completed system before seismic testing showing hinge locations.

24 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Damage Analysis As stated in NCHRP Synthesis 440, it is a fundamental need for the PBSD methodology to determine the type of damage and the likelihood that such damage will occur in the particular components of the structural system. This determination is of vital importance, as the damage sustained by a structure (and its nonstructural components) is directly relatable to the use or loss of a system after an earthquake. Therefore, there is a need to be able to reliably link structural and nonstructural response (internal forces, deformations, accelerations, and displacements) to damage. This is the realm of damage analyses, where damage is defined as discrete observable damage states (e.g., yield, spalling, longitudinal bar buckling, and bar fracture). Although the primary focus of the discussions is on structural components, similar considerations must be made for nonstructural components as well. NCHRP Synthesis 440 outlined an initial discussion on types of structural damage observed during historic earthquakes and laboratory experiments, prefaced the methods that have been developed to predict damage, identified structural details and concepts that could be used to reduce damage even in strong ground shaking, and reviewed post-event inspection tools. The new materials discussed in previous sections also apply to this discussion but are not repeated herein. Accurate damage prediction relies upon accurate definitions of performance limit states at the material level (i.e., strain limits) and the corresponding relationship between strain and displacement. Examples of recent research follow. Research by Feng et al. (2014b, 2014c) used finite element analysis validated by experimental test results to develop a model for predicting the tension strain corresponding to bar buckling. The model considers the impact of loading history on the boundary conditions of longitudinal bar restraint provided by the transverse steel. Goodnight et al. (2016a) identified strain limits to initiate bar buckling based on experimental results from 30 column tests (Equation 2). Following additional bidirectional tests on 12 columns, Equation 2 was revised to Equation 3. In addition, strain limit state equations were proposed for the compression strain in concrete to cause spiral yielding (Goodnight et al. 2017a). Goodnight et al. (2016b) also developed a new plastic hinge length model based on the data collected during those tests, which accounts for the actual curvature distribution in RC bridge columns. The revised model separates the strain penetration component from the flexural component while also recognizing that the hinge length for compression is smaller than that for tension. Brown et al. (2015) developed strain limit state (Equation 4) (tube wall local buckling) and equivalent viscous damping equations for reinforced concrete filled steel tubes (RCFSTs). The recommendations of the authors were based upon reversed cyclic tests of 12 RCFSTs of variable D/t (diameter to thickness) ratios. 0.03 700 0.1 (2)bucklingbar f E P f A s s yhe s ce g ε = + ρ − ′ 0.032 790 0.14 (3)bucklingbar f E P f A s s yhe s ce g ε = + ρ − ′ 0.021 9100 (4)tension buckling D t yε = − ≥ ε

Literature Review and Synthesis 25 where rs = reinforcement ratio, fyhe = expected yield strength of the steel tube (ksi), Es = elastic modulus of steel (ksi), P = axial load (kip), f ′ce = expected concrete strength (ksi), Ag = gross area of concrete (in.2), D = diameter of tube (in.), t = thickness of tube (in.), and ey = yield strain for steel (in./in.). Loss Analysis The PBSD combines the seismic hazard, structural, and damage analysis into a performance matrix that can be estimated into a loss metric. There are many loss metrics that can be used by, and that are important to, stakeholders and decision makers (discussed in detail in NCHRP Synthesis 440), but all these metrics can be boiled down to three main categories: deaths, dollars, and downtime. Bertero (2014) discussed earthquake lessons, in terms of loss, to be considered in both design and construction of buildings. At the beginning of 2010, two large earthquakes struck the Americas. The January 12, 2010, Haiti earthquake with a magnitude 7.0 produced about 300,000 deaths (second by the number of fatalities in world history after the 1556 Shaanxi, China earthquake). A month later, the February 27, 2010, Maule Chilean earthquake with a magnitude 8.8 (an energy release 500 times bigger than that from the Haiti earthquake) produced 500 deaths, most due to the resulting tsunami. However, the Chilean earthquake caused more than $30 billion of direct damage, left dozens of hospitals and thousands of schools nonoperational, and caused a general blackout for several hours, as well as the loss of service of essential communications facilities, crucial to take control of the chaotic after-earthquake situ- ation. Bertero (2014) compared the severity of both earthquakes and comments on their effects to life and the economy of the affected countries, as well as the features of the seismic codes or the absence of codes. An example of risk analysis with PBSD is utilized in Bensi et al. (2011), with the development of a Bayesian network (BN) methodology for performing infrastructure seismic risk assessment and providing decision support with an emphasis on immediate post-earthquake applications. A BN is a probabilistic graphical model that represents a set of random variables and their probabilistic dependencies. The proposed methodology consists of four major components: (1) a seismic demand model of ground motion intensity as a spatially distributed random field, accounting for multiple sources and including finite fault rupture and directivity effects; (2) a model for seismic performance of point-site and distributed components; (3) models of system performance as a function of component states; and (4) models of post-earthquake decision making for inspection and operation or shutdown of components. The use of the term Bayesian to describe this approach comes from the well-known Bayes rule, attributed to the 18th-century mathematician and philosopher Thomas Bayes: A B AB B B A B A( ) ( )( ) ( ) ( ) ( )= =Pr Pr Pr Pr Pr Pr (5) Pr(AB) is the probability of joint occurrence of Events A and B; Pr(A) is the marginal probability of Event A; Pr(A|B) is the conditional probability of Event A, given that Event B

26 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design has occurred; and Pr(B) is the marginal probability of Event B. The quantity Pr(B | A) is known as the likelihood of the observed Event B. Note that the probability of Event A appears on both sides of Equation 5. The Bayes rule describes how the probability of Event A changes given information gained about the occurrence of Event B. For discrete nodes, a conditional probability table is attached to each node that provides the conditional probability mass function (PMF) of the random variable represented by the node, given each of the mutually exclusive combinations of the states of its parents. For nodes without parents (e.g., X1 and X2 in Figure 12), known as root nodes, a marginal probability table is assigned. The joint PMF of all random variables X in the BN is constructed as the product of the conditional PMFs: (6) 1 p x p x Pa xi ii n∏( ) ( )( )= = Bensi et al. (2011) goes on to introduce BN models further and discusses how to incorporate BN-based seismic demand models into bridge design. The BN methodology is applied to modeling of random fields, construction of an approximate transformation matrix, and numer- ical investigation of approximation methods, including a discussion on the effect of correlation approximations on system reliability. Modeling component performance with BNs to capture seismic fragility of point-site components and distributed components, as well as modeling system performance of BNs with both qualitative and conventional methods, is explained. This reference goes on to identify efficient minimal link set (MLS), minimal cut set (MCS) formulations, optimal ordering of efficient MLS and MCS formulations, and heuristic augmen- tation that can be utilized with the BN methodology. Bensi et al. (2011) continues the PBSD process by addressing the owner decision-making process (see more discussion later in the report) and how to incorporate this model into that process. Two example problems are provided utilizing this methodology, including a California high-speed rail system that incorporates the bridge modeling into the example. Similarly, in Tehrani and Mitchell (2014), the seismic performance of 15 continuous four- span bridges with different arrangements of column heights and diameters was studied using incremental dynamic analysis (IDA). These bridges were designed using the Canadian Highway Bridge Design Code provisions (CSA 2006). The IDA procedure has been adopted by some guidelines to determine the seismic performance, collapse capacity, and fragility of buildings. Similar concepts can be used for the seismic assessment of bridges. Fragility curves can be devel- oped using the IDA results to predict the conditional probability that a certain damage state is exceeded at a given intensity measure value. Assuming that the IDA data are lognormally distributed, it is possible to develop the fragility curves at collapse (or any other damage state) by computing only the median collapse capacity and the logarithmic standard deviation of the IDA results for any given damage state. The fragility curves can then be analytically computed using Equation 7 as follows: ln ln (7)50% TOT P failure S x x S a a C( )( ) ( )= = Φ − β     where function F = cumulative normal distribution function, SCa 50% = median capacity determined from the IDA, and βTOT = total uncertainty caused by record-to-record variability, design requirements, test data, and structural modeling. Figure 12. A simple BN.

Literature Review and Synthesis 27 The seismic risk associated with exceeding different damage states in the columns, includ- ing yielding, cover spalling, bar buckling, and structural collapse (i.e., dynamic instability) was predicted. Some simplified equations were derived for Montreal, Quebec, Canada, to estimate the mean annual probability of exceeding different damage states in the columns using the IDA results. Repair and retrofit procedures are linked to loss predictions, as outlined in the FHWA’s retro- fitting manual (Buckle et al. 2006). Several chapters/articles address analysis, methodologies, effects, analytical tools, and costs for retrofit and repairs to mitigate damage or return a structure to a serviceable condition. Zimmerman et al. (2013) is one example, in which numerical techniques and seismic retrofit solutions for shear-critical reinforced concrete columns was investigated, utilizing test data of a reinforced concrete column with widely spaced transverse reinforcement. The study focused on the analysis method of nonlinear trusses and the retrofit option known as supplemental gravity columns, which is an example of how loss prediction and the analysis process are linked and should be iterated through PBSD. Organization-Specific Criteria for Bridges and Project-Specific Criteria NCHRP Synthesis 440 has two sections of criteria: organization-specific criteria for bridges and project-specific criteria. New information for both of these sections since NCHRP Synthesis 440 published is combined. The California DOT (Caltrans) Caltrans is currently updating their Seismic Design Criteria (SDC) to specify requirements to meet the performance goals for newly designed Ordinary Standard and Recovery Standard con- crete bridges. Nonstandard bridges require Project-Specific Seismic Design Criteria, in addition to the SDC, to address their nonstandard features. For both standard and nonstandard bridges, Caltrans is also categorizing their inventory in terms of Ordinary Bridges, Recovery Bridges, and Important Bridges. Some states have had issues with terms like Important or Essential, as a bridge is considered important to those that utilize each bridge. Caltrans is using these terms to correlate with loss analysis of an owner’s infrastructure and the time to reopen the bridge to support lifeline and recovery corridors. The bridge performance is also evaluated using a dual-seismic hazard; for Caltrans SDC they are listed as a Safety Evaluation Earthquake (SEE) for Ordinary Bridges. Both SEE and Functional Evaluation Earthquake (FEE) for Recovery Bridges are summarized in Table 6. Caltrans SDC revisions will also provide updates to the design parameters in Chapter 3 of the SDC and updates to both the analysis methods and displacement ductility demand values in Chapter 4 of the SDC. The adjustments to the displacement ductility demand values are revised to limit the bridge displacements beyond the initial yielding point of the ERE, specifically if a recovery standard bridge is being designed. The revisions to their SDC is an example of how PBSD is being gradually introduced as a better method of dealing with the hazards, soil–structure interaction, analysis tools, methodologies, material properties, damage states, performance, and loss. Similar revisions are being made to Seismic Design Specifications of Highway Bridges, as detailed in Japan Road Association (JRA) revisions in 2012. A synopsis of the revisions is provided in Kuwabara et al. (2013). The JRA specifications apply to Japanese road bridges and consist of five parts: Part I, Common; Part II, Steel Bridges; Part III, Concrete Bridges; Part IV, Substruc- tures; and Part V, Seismic Design. The revisions are based on improvements in terms of safety,

28 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design serviceability, and durability of bridges. Based on those lessons, design earthquake ground motions corresponding to the subduction-type earthquake were revised, and the requirements for easy and secure maintenance (inspection and repair works) for the bridges were clearly specified. JRA has clarified their performance of ERE conventionally reinforced columns for a dual-level (SPL 2 and SPL 3) seismic performance evaluation, as summarized in Table 7. The JRA 2012 revisions also address connection failures between reinforced concrete steel piles and the pile-supported spread footing to improve structural detailing and performance at the head of the piles. This is similar to research performed by the University of Washington, see Stephens et al. (2015) and Stephens et al. (2016) for both Caltrans and Washington State DOT, respectively, to evaluate capacity protecting this region and even considering the development of plastic hinges at these locations for combined hazard events or large lateral spreading and liquefaction occurrences. Caltrans also funded a study by Saini and Saiidi (2014) to address probabilistic seismic design of bridge columns using a probabilistic damage control approach and reliability analysis. Source: Caltrans. BRIDGE CATEGORY SEISMIC HAZARD EVALUATION LEVEL POST EARTHQUAKE DAMAGE STATE EXPECTED POST EARTHQUAKE SERVICE LEVEL Table 6. Caltrans draft proposed seismic design bridge performance criteria. SPL2 SPL3 Note: SPL1: Fully operational is required. Limit state of bridge is serviceability limit state. Negligible structural damage and nonstructural damage are allowed. Table 7. Seismic performance of bridge and limit states of conventionally reinforced concrete bridge column.

Literature Review and Synthesis 29 The probabilistic damage control approach uses the extent of lateral displacement nonlinearity defined by Damage Index (DI) to measure the performance of bridge columns. DI is a measure of damage from the lower measure of zero damage to the ultimate measure of a collapse mecha- nism for an element that has been subjected to base excitations. The performance objective was defined based on predefined apparent Damage States (DS), and the DS were correlated to DIs based on a previous study at the University of Nevada, Reno (Figure 13) (Vosooghi and Saiidi 2010). A statistical analysis of the demand damage index (DIL) was performed to develop fragility curves (load model) and to determine the reliability index for each DS. The results of the reliability analyses were analyzed, and a direct probabilistic damage control approach was developed to calibrate design DI to obtain a desired reliability index against failure. The calculated reliability indices and fragility curves showed that the proposed method could be effectively used in seismic design of new bridges, as well as in seismic assessment of existing bridges. The DS and DI are summarized with performance levels defined by Caltrans in Table 8, which shows the correlation between DS and DI. Figure 14 shows a fragility curve using lognormal distribution. Figure 15 shows both the fragility curves (upper two graphs) and reliability indices (lower two graphs) for four column bents (FCBs), with 4-foot diameter columns that are 30 feet in length in Site D for both the 1000 year and 2500 year seismic events. Note: O-ST = ordinary standard bridge, O-NST = ordinary nonstandard bridge, Rec. = recovery bridge, Imp. = important bridge, and NA = not applicable. Damage State (DS) Service to Public Service to Emergency Emergency Repair Design Damage Index (DI) Earthquake Levels (Years) Table 8. Design performance levels. DI P (D I { D S) Figure 13. Correlation between DS and DI.

30 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Figure 14. Fragility curve. 100% 80% 60% 40% 20% 0% 0.00 0.20 0.40 0.60 0.80 1.00 P (D I L ) DIL 4.0 3.0 2.0 1.0 0.0 R el ia bi lit y In de x | D S DS3 DS4 DS5 DS6 Damage State (DS) 6.0 5.0 4.0 3.0 2.0 1.0 0.0 R el ia bi lit y In de x | D S DS3 DS4 DS5 DS6 Damage State (DS) (a) (b) (d)(c) 0.00 0.20 0.40 0.60 0.80 1.00 DIL 100% 80% 60% 40% 20% 0% P (D I L ) Figure 15. Fragility curves and reliability indices for FCBs with 4-foot columns in Site D. The Oregon DOT The Oregon DOT is developing a global plan for addressing resiliency in order to improve recovery for the next Cascadia Earthquake and Tsunami, using PBSD in terms of applying applicable hazards, identifying critical services, developing a comprehensive assessment of structures and systems, and updating public policies. The resilience goals are similar to those discussed at the beginning of this chapter, with the following statement: Oregon citizens will not only be protected from life-threatening physical harm, but because of risk reduction measures and pre-disaster planning, communities will recover more quickly and with less continuing vulnerability following a Cascadia subduction zone earthquake and tsunami.

Literature Review and Synthesis 31 Research has shown that the next great (magnitude 9.0) Cascadia subduction zone earth- quake is pending, as shown in Figure 16. This comparison of historical subduction zone earthquakes in northern California, Oregon, and Washington covers 10000 years of seismic history. The evidence of a pending event has made decision makers and the public take notice and put forth resources to develop strategies revolving around PBSD. Oregon’s performance-based features are modified from NCHRP Synthesis 440 to account for a third hazard condition: Cascadia Subduction Zone Earthquake (CSZE) in Oregon DOT’s Bridge Design and Drafting Manual—Section 1, Design (Oregon DOT 2016a; see also Oregon DOT 2016b). Design of new bridges on and west of US 97 references two levels of perfor- mance criteria: life safety and operational. Design of new bridges east of US 97 requires life safety criteria only. Seismic design criteria for life safety and operational criteria are described as follows. • “Life Safety” Criteria: Design all bridges for a 1,000-year return period earthquake (7 percent prob- ability of exceedance in 75 years) to meet the “Life Safety” criteria using the 2014 USGS Hazard Maps. The probabilistic hazard maps for an average return period of 1,000 years and 500 years are available at ODOT Bridge Section website, but not available on USGS website. To satisfy the “Life Safety” criteria, use Response Modification Factors from LRFD Table 3.10.7.1-1 using an importance category of “other.” • “Operational” Criteria: Design all bridges on and west of US 97 to remain “Operational” after a full rupture of Cascadia Subduction Zone Earthquake (CSZE). The full-rupture CSZE hazard maps are available at the ODOT Bridge Section website. To satisfy the “Operational” criteria, use Response Modification Factors from LRFD Table 3.10.7.1-1 using an importance category of “essential.” When requested in writing by a local agency, the “Operational” criteria for local bridges may be waived. The CSZE is a deterministic event, and a deterministic design response spectrum must be generated. To allow for consistency and efficiency in design for the CSZE, an application for generating the design response spectra has been developed by Portland State University (Nako et al. 2009). AASHTO guide specifications values for Table 3.4.2.3-1 are modified into two tables for (1) values of Site Factor, Fpga, at zero-period on the acceleration spectrum and (2) values of Site Factor, Fa, for short-period range of acceleration spectrum. Table 3.4.2.3-2 is replaced with values of Site Factor, Fv, for long-period range of acceleration spectrum. For seismic retrofit projects, the lower level ground motion is modified to be the CSZE with full rupture, as seen in Table 9. Performance levels, including performance level zero (PL0), are specified based on bridge importance and the anticipated service life (ASL) category required. Source: OSSPAC (2013). Figure 16. Cascadia earthquake timeline.

32 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design The South Carolina DOT South Carolina Department of Transportation (South Carolina DOT) has updated its geo- technical design manual (South Carolina DOT 2019). Chapters 12, 13, and 14 for geo technical seismic analysis, hazard, and design, respectively, have been updated to current practices and research, including incorporation of PBSD hazard prediction. South Carolina DOT is also updating their site coefficients to be more appropriate for South Carolina’s geologic and seismic conditions; see Andrus et al. (2014). Note that with the revisions, South Carolina DOT issued a design memorandum in November 2015 that revised the substructure unit quantitative damage criteria (maximum ductility demand) table (Table 7.1 of the SCDOT Seismic Design Specifications for Highway Bridges). See Table 10. The Utah DOT The Utah DOT and Brigham Young University (see Franke et al. 2014a, 2014b, 2015a, 2015b, 2015c, 2016) are researching the ability for engineers to apply the benefits of the full performance- based probabilistic earthquake analysis without requiring specialized software, training, or education. There is an emphasis on differences between deterministic and performance-based procedures for assessing liquefaction hazards and how the output can vary significantly with these two methodologies, especially in areas of low seismicity. Guidance is provided regarding when to use each of the two methodologies and how to bind the analysis effort. Additionally, a simplified performance-based procedure for assessment of liquefaction triggering using liquefaction loading maps was developed with this research. The components of this tool, as well as step-by-step procedures for the liquefaction initiation and lateral spread displacement models, are provided. The tool incorporates the simplified performance-based procedures determined with this research. National Highway Institute Marsh et al. (2014) referenced a manual for the National Highway Institute’s training course for engineers to understand displacement-based LRFD seismic analysis and design of bridges, which is offered through state agencies and open to industry engineers and geotechnical engi- neers. This course helps designers understand the principles behind both force-based AASHTO (AASHTO 2014) and displacement-based AASHTO (AASHTO 2011) methodologies, including a deeper understanding of what performance means in a seismic event. Other similar courses are also being offered to industry and are improving the understanding of practicing engineers. Federal Emergency Management Agency The Federal Emergency Management Agency (FEMA) has developed a series of design guidelines for seismic performance assessment of buildings and three of the five documents EARTHQUAKE GROUND MOTION BRIDGE IMPORTANCE and SERVICE LIFE CATEGORY Table 9. Modifications to minimum performance levels for retrofitted bridges.

Literature Review and Synthesis 33 are referenced in FEMA (2012a, 2012b, 2012c). A step-by-step methodology and explanation of implementation are provided for an intensity-based assessment and for a time-based assess- ment. The process of identifying and developing appropriate fragility curves is demonstrated. A software program called Performance Assessment Calculation Tool has also been developed with a user manual that is included in the FEMA documents to help engineers apply PBSD to the building industry. Japan Road Association The Japan Road Association (JRA) Design Specifications have been revised based on the performance-based design code concept in response to the international harmonization of design codes and the flexible employment of new structures and new construction methods. Figure 17 shows the code structure for seismic design using the JRA Design Specifications. The performance matrix is based on a two-level ground motion (Earthquakes 1 and 2), with the first one based on an interpolate-type earthquake and magnitude of around 8, and the second one with a magnitude of around 7 with a short distance to the structure. Kuwabara et al. (2013) outlined the incremental revisions from the JRA Design Specif i- cations between 2002 and 2012. These revisions include, but are not limited to, the ductility design method of reinforced concrete bridges, plastic hinge length equation, evaluation of hollow columns, and the introduction of high-strength steel reinforcement. Following the 2016 earthquake in Kumamoto, Japan, a new version of the JRA Design Specifications is in the works. Note: Analysis for FEE is not required for OC III bridges. Source: South Carolina DOT (2015). Design Earthquake Operational Classification (OC)Bridge Systems Table 10. South Carolina DOT substructure unit quantitative damage criteria (maximum ductility demand ld).

34 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Identification of Knowledge Gaps The resources to develop guide specifications for PBSD are improving with examples such as the upcoming Seismic Design Criteria, Version 2 from Caltrans, which will address aspects of PBSD and the building industry’s efforts to develop practices in PBSD and tools for engineers and owners to collaborate on solutions based on performance criteria and expectations. There is still a perception that the bridge industry could better predict likely performance in large, damaging earthquakes than is being done at the present, and there are still gaps in that knowledge base that need to be closed. Most of the knowledge gaps listed in Marsh and Stringer (2013) are still applicable today; see Table 11. The technology readiness levels represent what has been developed and used; what research is done, ongoing, and being discussed; and what only exists in concept. Knowledge gaps certainly exist in all facets of PBSD; however, other key knowledge gaps beyond those listed in NCHRP Synthesis 440 (Marsh and Stringer 2013) that should be closed in order to improve the implementation of PBSD are covered. Objectives of Codes Mandated Specifications Overall Goals Functional Requirements (Basic Requirements) Performance Requirement Level Verification Methods and Acceptable Solutions Can be Modified or May be Selected with Necessary Verifications Importance, Loads, Design Ground Motion, Limit States Principles of Performance Verification Verifications of Seismic Performances (Static and Dynamic Verifications) Evaluation of Limit States of Members (RC and Steel Columns, Bearings, Foundations and Superstructure) Unseating Prevention Systems Principles of Seismic Design Figure 17. Code structure for seismic design using JRA design specifications. TRL Description 0-25 25-50 50-75 75-100 1 PBSD concept exists 2 Seismic hazard deployable 3 Structural analysis deployable 4 Damage analysis deployable 5 Loss analysis deployable 6 Owners willing and skilled in PBSD 7 Design guidelines 8 Demonstration projects 9 Proven effectiveness in earthquake Technology Readiness Level (TRL) % of Development Complete Table 11. Technology readiness levels for PBSD.

Literature Review and Synthesis 35 Gaps related to structural analysis can include minimum and expected properties for reinforcing greater than Grade 80, stainless steel, and other materials that can improve serviceability and in some conditions performance. Oregon DOT has been using stainless steel in their bridges located along the coastline and other highly corrosive environments to extend the service life of the bridge; however, many of these locations are also prone to large CSZE and the use of these materials in earthquake resisting elements is still being developed. In the State of Washington’s resiliency plan, outlined in Washington State Emergency Management Council–Seismic Safety Committee (2012), what is missing is a link between damage levels and return to service. This is a knowledge gap given what we know structurally and what this report is suggesting as a desired goal for post-earthquake recovery. Gaps related to decision makers can include bridge collapse. It is not intended that the PBSD guide specifications will address tsunami events, but the JRA specifications do address tsunami as well as landslide effects. Figures 18 and 19 are examples of these other types of failure systems and show the collapse of bridges caused by effects other than ground motion (Kuwabara et al. 2013). The decision to combine these types of effects with a seismic hazard, even combining liquefaction, down drag, and lateral spreading effects, needs additional clarification and is currently left up to the owner to assess implications of probability, safety, and cost ramifications. Liang and Lee (2013) summarized that in order to update the extreme event design limit states in the AASHTO 2014, combinations of all nonextreme and extreme loads need to be formulated on the same probability-based platform. Accounting for more than one-time variable load creates a complex situation, in which all of the possible load combinations, even many that are not needed for the purpose of bridge design, have to be determined. A formulation of a criterion to determine if a specific term is necessary to be included or rejected is described, and a comparison of the value of a given failure probability to the total pre-set permissible design failure probability can be chosen as this criterion. Figure 18. Collapse of bridge due to landslide. (Note: Reprinted courtesy of the National Institute of Standards and Technology, U.S. Department of Commerce. Not copyrightable in the United States). Source: Kuwabara et al. (2013).

36 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design While the seismic hazard definition was once thought to be relatively well understood, there is a growing knowledge gap related to the effect of rotation angle on intensity of ground motions and how the use of a geometric mean of the motions, or other methods of including the effect of rotation angle (RotDxx), should be incorporated into seismic design. This issue is not specific to PBSD; like all seismic design methods, PBSD is reliant on a full understanding of the hazard definition for proper implementation. The knowledge gaps identified in NCHRP Synthesis 440 are still applicable. Many of these knowledge gaps will become evident to both engineers and decision makers as the PBSD guidelines are developed. Overall, the baseline information to develop PBSD guide specifica- tions are in place. Industry’s end goal of understanding the relationship between risk-based decision making and design decisions and methodologies to meet performance goals is going to be an iterative process. Figure 19. Collapse of bridge due to tsunami. (Note: Reprinted courtesy of the National Institute of Standards and Technology, U.S. Department of Commerce. Not copyrightable in the United States). Source: Kuwabara et al. (2013).

Performance-based seismic design (PBSD) for infrastructure in the United States is a developing field, with new research, design, and repair technologies; definitions; and methodologies being advanced every year.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 949: Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design presents a methodology to analyze and determine the seismic capacity requirements of bridge elements expressed in terms of service and damage levels of bridges under a seismic hazard. The methodology is presented as proposed AASHTO guidelines for performance-based seismic bridge design with ground motion maps and detailed design examples illustrating the application of the proposed guidelines and maps.

Supplemental materials to the report include an Appendix A - SDOF Column Investigation Sample Calculations and Results and Appendix B - Hazard Comparison.

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