Determination of Remaining Fatigue Life of Welded Stud Details on Overhead Aluminum Sign Panels in Virginia

摘要

Some overhead highways signs in Virginia using a specific welded threaded stud and clip connection have failed while in service. From inspection of the signs it was determined that the failure was caused by fatigue of the weld connecting the threaded stud to the back of the sign panel. It was also observed that lower edge connections failed first and the failures progressed upwards in an unzipping pattern. A combination of natural and truck-induced wind gusts is the cause for the fatigue failure. Although signs with these connections are no longer produced by VDOT and all production was halted in early 2004, there are still approximately 4,000 signs in Virginia with this connection detail. The objective of the research project described here in was to determine priorities for an inspection and retrofitting plan for the remainder of the signs in Virginia. Specifically an S-N curve, which is a plot of stress range versus the number of cycles to failure, was to be developed to aid in predicting the remaining service life of sign panels using this connection detail.