EVALUATION OF REPAIR PROCEDURES FOR WEB GAP FATIGUE DAMAGE

Connection plates of cross-frame diaphragms not rigidly attached to tension flanges can develop fatigue cracking in the unstiffened web gap due to the out-of-plane distortion. This report investigates repair procedures for fatigue damage in the web gap of steel highway bridges. The procedures investigated include drilling holes at crack tips, flame-cutting holes to remove extensively cracked regions, and gouging and rewelding. In addition, rigid attachment retrofits of tight-fit and cut-short connection plate details are examined. The evaluation of these repairs are made by monitoring their implementation on an in-service bridge, laboratory fatigue testing of simulated repairs, and finite element analysis. All three crack repair procedures were found to be viable. However, procedures outlined must be followed to achieve the quality in the repair that will insure continued safe use of the bridge throughout its remaining life. The results indicate that the degree of finish given to the repair is as important as satisfying the prescribed repair criteria.