Fatigue analysis of overhead sign support structures

Sign structures stand along highways and roadways to guide motorists to their destination. Such structures are repeatedly subjected to natural wind load and gusts from vehicles passing underneath. Over time, the members within the structure may begin to succumb to fatigue due to cyclical loading. In this paper an algorithm to determine the fatigue life of an overhead four-chord truss sign structure is presented. The algorithm includes a time varying natural wind loading and a finite element model. The stress history of selected critical elements is extracted from the model’s solution. Complete stress ranges are counted and a linear damage accumulation method is used to find the fatigue life of some critical members. The fatigue life analysis is carried out by simulating pristine condition and three different damage scenarios.