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| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
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| Publication Number: FHWA-HRT-14-093 Date: December 2014 |
Publication Number:
FHWA-HRT-14-093
Date: December 2014 |
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Bolted connections are a critical part of nearly every steel bridge. Individual components are assembled together in the field using high-strength bolts, and frictional connections are specified to ensure appropriate connection performance throughout the life of the bridge. The coatings used on the faying surface of the connections must demonstrate a predetermined friction coefficient for the overall connection to attain its required frictional resistance. This friction coefficient is defined by a test method governed by the Research Council for Structural Connections (RCSC). In recent years, there has been concern within the bridge engineering community that ambiguities within the test method might increase the variability of reported friction coefficients.
This report outlines the findings and recommendations from a round-robin laboratory study on slip coefficients of organic zinc-rich primers for steel bridges. Prior to this work, variability of slip coefficients attained for the same coatings were noted by coating manufacturers despite no changes in formulation. This study was conducted to quantify the variability and recommend changes to RCSC to reduce the variability. Overall, it was found that participating labs followed the RCSC procedure but were sometimes reporting very different slip coefficients for identical coatings. The major finding was the manner in which each lab measured slip displacement, which contributed to the greatest variability in frictional coefficient results. It is recommended that RCSC clarify its intended method for measuring slip deformation. Once implemented, it is anticipated that the revised test method will appropriately quantify coating frictional coefficients and thus ensure proper connection performance. This report would benefit those in charge of specifying and testing steel bridge coatings including coating manufactures, RCSC, State transportation departments, researchers, and design consultants.
Jorge E. Pagán-Ortiz
Director, Office of Infrastructure
Research and Development
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The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.
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