Estimate of the steel bridges fatigue life by application of the fracture mechanics

Abstract

The bridge elements are subjected to the low-amplitude cyclic loading, causing the fatigue as the main problem that limits the carrying capacity and remaining working life of a structure. Identifying the parts prone to fatigue, inspection control, preventive maintenance, successful reinforcing and repair plans, secure the satisfying characteristics of a bridge during its working life.For a new structure is important that elements subjected to fatigue are so designed to avoid the danger of the fatigue fracture. The fracture mechanics represents a useful tool for analyzing the fatigue crack growth in steel elements. The relevant parameters for the remaining working life estimate are the load level and frequency and the stress concentration.A method, based on the Paris’ law, for predicting the remaining fatigue working life of steel bridges, is proposed and verified on an actual bridge. The considered bridge was found to be safe against the fatigue fracture, both for the present and the future increased load, since it was verified that it has the reserve with respect to fatigue life. Based on obtained results, one can conclude that the fatigue working life of a bridge and its elements can be estimated based on application of the LEFM (linear elastic fracture mechanics) concept.