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Suggested Citation:"Introduction ." National Academies of Sciences, Engineering, and Medicine. 2011. Validation of LRFD Metal Loss and Service-Life Strength Reduction Factors for Metal-Reinforced Systems. Washington, DC: The National Academies Press. doi: 10.17226/14587.
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Research Results Digest 364 October 2011 INTRODUCTION This digest summarizes the results of research conducted as a follow-up to NCHRP Project 24-28, “LRFD Metal Loss and Service-Life Strength Reduction Fac- tors for Metal Reinforcements in Geotech- nical Applications.” NCHRP Project 24-28 assessed and improved models for corro- sion potential, metal loss, and service life of metal-reinforced systems used in retaining walls, and highway cuts and fills. The proj- ect compiled a performance database for earth reinforcements that describes the exist- ing conditions and measured corrosion rates of in-service reinforcements at approxi- mately 170 sites across the United States and Europe. Data were obtained from rein- forcement types typical of mechanically stabilized earth systems (MSES) as well as installations of rock bolts and ground anchors. These data were used to identify and group trends related to the character of the fill or in-situ earth materials, reinforce- ment type, and various site conditions. Based on these trends, the reliability of metal-loss modeling and service-life pre- dictions were computed and the corre- sponding biases with respect to nominal tensile strengths used in design were evalu- ated and then used to calibrate appropriate resistance factors for use in load and resis- tance factor design (LRFD). The results, findings, and conclusions of NCHRP Proj- ect 24-28 were published as NCHRP Report 675: LRFD Metal Loss and Service-Life Strength Reduction Factors for Metal- Reinforced Systems.1 MSES reinforcements consist of galva- nized steel strips, mats, or grids. The possi- bility of metal loss is considered in design through selection of fill materials that are relatively nonaggressive, and the use of sacrificial steel in the reinforcement cross section. NCHRP Project 24-28 found that estimates of sacrificial steel requirements and remaining strength were reliable for reinforcements surrounded by high- or good-quality fill materials. However, the performance estimates for reinforcements in marginal-quality fills were highly uncer- tain. Also, the estimated performance of galvanized reinforcements after the base steel was exposed by depletion of the zinc coating was subjective due to a lack of data from older installations. This situation could VALIDATION OF LRFD METAL LOSS AND SERVICE-LIFE STRENGTH REDUCTION FACTORS FOR METAL-REINFORCED SYSTEMS This digest summarizes key findings of NCHRP Project 24-28A, “Validate the Results of NCHRP Project 24-28,” conducted by McMahon & Mann Consulting Engineers, P.C., under the direction of the principal investiga- tor, Kenneth L. Fishman. The digest is based on the project final report authored by Dr. Fishman. The full text of the project final report is avail- able for download at http://apps.trb.org/cmsfeed/TRBNetProject Display.asp?ProjectID=727. Responsible Senior Program Officer: E. T. Harrigan NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM 1Available for download at http://www.trb.org/ Main/Blurbs/165158.aspx.

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TRB’s National Cooperative Highway Research Program (NCHRP) Research Results Digest 364: Validation of LRFD Metal Loss and Service-Life Strength Reduction Factors for Metal-Reinforced Systems summarizes the results of research to further validate some key results of a project that resulted in publication of NCHRP Report 675: LRFD Metal Loss and Service-Life Strength Reduction Factors for Metal-Reinforced Systems.

NCHRP Report 675 explores the development of metal loss models for metal-reinforced systems that are compatible with the American Association of State Highway and Transportation Officials' Load and Resistance Factor Design (LRFD) Bridge Design Specifications.

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