Investigation of Material Requirements for Highway Guardrail Systems (2022)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

2022 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 1020 Investigation of Material Requirements for Highway Guardrail Systems Chuck A. Plaxico Ethan M. Ray Roadsafe LLC Canton, ME Subscriber Categories Design • Materials • Safety and Human Factors Research sponsored by the American Association of State Highway and Transportation Ofcials in cooperation with the Federal Highway Administration

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRB’s relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement, rather than to substitute for or duplicate, other highway research programs. Published research reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to https://www.mytrb.org/MyTRB/Store/default.aspx Printed in the United States of America NCHRP RESEARCH REPORT 1020 Project 22-40 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-68758-4 Library of Congress Control Number 2022948278 © 2022 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trade- marks of the National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, APTA, FAA, FHWA, FTA, GHSA, or NHTSA endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; the FHWA; or the program sponsors. The Transportation Research Board does not develop, issue, or publish standards or speci- fications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names or logos appear herein solely because they are considered essential to the object of the report.

e National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. e National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. e National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. e three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. e National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.nationalacademies.org. e Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. e mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. e Board’s varied activities annually engage about 8,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. e program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.

C O O P E R A T I V E R E S E A R C H P R O G R A M S CRP STAFF FOR NCHRP RESEARCH REPORT 1020 Christopher J. Hedges, Director, Cooperative Research Programs Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program Sid Mohan, Associate Program Manager, Implementation and Technology Transfer, National Cooperative Highway Research Program Christopher T. McKenney, Senior Program Officer Robert Turner II, Senior Program Assistant Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications Doug English, Senior Editor NCHRP PROJECT 22-40 PANEL Field of Design—Area of Vehicle Barrier Systems Timothy J. Ruelke, Florida Department of Transportation, Gainesville, FL (Chair) Amitabha Bandyopadhyay, SUNY Farmingdale, Farmingdale, NY Richard Clausius, ArcelorMittal R&D, East Chicago, IN Erik O. Emerson, Wisconsin Department of Transportation, Madison, WI John E. Grieco, STV, Inc., Boston, MA Christopher Hahin, Illinois Department of Transportation, Springfield, IL Stephanie Huang, Arizona Corporation Commission, Phoenix, AZ Jose S. Lima, Rhode Island Department of Transportation, Providence, RI Gregory Allen Neece, Valtir, Addison, TX Phil Shawk, Gregory Industries, Canton, OH Kevin Skero, Nucor Steel Marion, Inc., Charleston, SC Eduardo Arispe, FHWA Liaison

By Christopher T. McKenney Staff Officer Transportation Research Board NCHRP Research Report 1020: Investigation of Material Requirements for Highway Guard- rail Systems presents a state-of-the-art investigation of material requirements for highway guardrail systems and their components to provide better consistency with current road- side safety hardware requirements based on a comprehensive analytical program to identify knowledge gaps within the current state of the practice. In addition, the report includes pro- posed language for consideration by AASHTO to incorporate the research results in the next update of AASHTO M 180. This report will be of immediate interest to design and material engineers. Many states use AASHTO and ASTM standard specifications for their guardrail com- ponents. However, changes to the state of practice and to guardrail materials have created a need to revise AASHTO Standard Specification M 180-18, Corrugated Sheet Steel Beams for Highway Guardrail, and its associated material standards, including those referenced in M 180-18. A lack of consistent standard specifications can increase fabrication costs for hardware suppliers and ultimately transportation agencies. A manufacturer can spend a significant amount of resources matching one state’s standard specifications only to start completely over to match those of another state. Consistency of specifications can also help to increase competition, allowing for the possibility of lower hardware costs for transportation agencies. Some examples of developments in materials and the state of practice for highway guard- rail systems that are not currently addressed by AASHTO M 180-18 include: • The asymmetrical W-beam to thrie-beam transition section; • Inconsistency in the material requirements for thrie-beam terminal transitions and connections; • Use of high-strength steel bolts connecting thrie-beam terminal connectors to rigid barriers; • Multiple slot patterns for thrie-beam terminal connectors, thrie-beams, and W-beam rails; • Lack of consistent markings for components of the highway guardrail system; • Changes to applicable locations and geometric equivalents for ASTM standard bolts; • Use of multiple grades for steel posts; • Lack of guidance for shop-bent W-beam or thrie-beam rails (e.g., longitudinal radius of curve, radius tolerances, marking of beam radius to aid maintenance); • Lack of changes to the appropriate dimensions and tolerances (metric and inch) for holes in steel guardrails and posts; • Lack of inclusion of anchor wire rope standards; • Lack of standards for swage fittings; F O R E W O R D

• Changes to bolt tolerance, shape, and torque requirements; • Lack of paint and thermal spray specifications for guardrail beams and posts to meet the requirements for Type III guardrails; • Implications of the greater longevity of painted weathering steels compared to ordinary carbon steels; and • Need for specifications for stainless steel beams, posts, and bolting to meet the require- ments for Type IV guardrails. Recent years have seen an increased focus on the performance of roadside hardware. Therefore, research was needed to verify that transportation agencies are specifying and using correct materials in their highway guardrail systems. Under NCHRP Project 22-40, “Update to AASHTO M 180-18 and Associated Highway Guardrail Specifications,” Roadsafe, LLC was asked to (1) perform a comprehensive review of AASHTO M 180-18 and its associated AASHTO and ASTM standards, and (2) propose language for consideration by AASHTO to incorporate the research results in the next update of AASHTO M 180. Appendices A and B, which contain the proposed update, can be found on the project description page for NCHRP Project 22-40 (https://apps.trb.org/ cmsfeed/TRBNetProjectDisplay.asp?ProjectID=4586).

1 Chapter 1 Introduction 1 1.1 Project Objective 1 1.2 Background 3 Chapter 2 Literature Review 3 2.1 History of AASHTO M 180 6 2.2 Review of Current AASHTO M 180 Specification 13 2.3 Task Force 13, A Guide to Standardized Highway Barrier Hardware 18 2.4 States’ Use 24 2.5 Manufacturer Use 24 2.6 Survey of Practice 24 2.7 Equivalent Material Types 29 2.8 Documentation of Material Properties for Test Articles per MASH 38 Chapter 3 Deficiencies Identified in AASHTO M 180-18 39 Chapter 4 Deficiencies and Proposed Updates to AASHTO M 180-18 39 4.1 Terminology 40 4.2 Transition Beams 41 4.3 Terminal Connectors 42 4.4 Steel Guardrail Posts 44 4.5 Timber Guardrail Posts 44 4.6 Blockouts 45 4.7 Wire Rope and Swage Fittings Used for Anchorages 45 4.8 Bridge Railings 46 4.9 Fasteners 48 4.10 Sheet Steel Mechanical Properties 52 4.11 Sheet Steel Chemical Properties 53 4.12 Sheet Steel Thickness and Tolerances 54 4.13 Manufacturing 56 4.14 Galvanizing and Coatings 59 4.15 Marking 62 4.16 Drawings 66 4.17 Assembly Section 66 4.18 Uncategorized Updates and Deficiencies 70 Chapter 5 Summary and Conclusions 70 5.1 Summary 71 5.2 Conclusions 77 References C O N T E N T S

80 Appendix A Proposed AASHTO M 180 Specification Update 80 Appendix B Proposed AASHTO M 180 Specification Update with Redline Strikeout 80 Appendix C Commentary for AASHTO M 180 Updates 80 Appendix D Commentary for AASHTO M 180 Updates with Redline-Strikeout 81 Appendix E Components Included in TF13 Hardware Guide Used for W-Beam and Thrie-Beam Hardware Systems 87 Appendix F Survey of Practice 112 Appendix G Review of Mechanical Properties for Corrugated Sheet Steel Used in Guardrail Field Installations Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at nap.nationalacademies.org) retains the color versions.