Probabilistic fatigue and fracture analyses of steel bridges

According to a study conducted by the ASCE Committee on Fatigue and Fracture Reliability, 80-90% of failures in steel structures are related to fatigue and fracture. Therefore, fatigue and fracture reliability is an important concern for steel bridges. In this study, the finite strip method is coupled with either the fatigue approach proposed by Wirsching, or the linear-elastic fracture mechanics (LEFM) approach as proposed by Harris (In: Sundararajan C, Ed. Probabilistic structural mechanics handbook [chapter 7]. New York: Chapman Hall Ltd.; 1995. p 106-45.), for fatigue reliability analysis of steel highway bridges. The flat shell strips are employed to model the concrete slab and steel girders, while a connection strip is developed by means of the penalty function method in order to take into account the eccentricity of the top flange of girder. The loading effects are modeled by the fatigue truck developed by Laman and Nowak (Journal of Stuctural Engineering ASCE 1996:726). At each sampling point with given values of slab thickness and modulus ratio, a finite strip analysis of the bridge under fatigue truck is carried out, and the stress ranges at the fatigue-prone detail are calculated. According to these stress ranges and intended service life, the fatigue failure probability can be evaluated using the fatigue approach or the LEFM approach. After the failure probability is integrated over all sampling points, the fatigue reliability of the bridge is determined. Numerical examples are presented to illustrate the proposed methodology. (C) 2003 Elsevier Science Ltd. All rights reserved.