Fatigue crack initiation and propagation in piles of integral abutment bridges

A new continuum damage modeling approach of "successive initiation" is used to determine the location of a thermomechanical fatigue crack initiation and the propagation path and rate in piles of integral abutment bridges. A global-local modeling approach is introduced to determine the critical location in the pile where a crack is initiated using a 3-dimensional nonlinear finite element model and to implement "successive initiation." A simulated case study is used to showcase the multistep procedure. The results indicate that for a pile subjected to the maximum stress, the first fatigue-induced crack initiates in the tip of the flange at the element immediately below the abutment. Several other cracks at different locations form in the flange of the pile while the initial crack continues to propagate in the flange to the web. The crack propagation rate increases as more cracks initiate in the flange. The propagation rate decreases when the crack reaches the web. Based on the case study presented, a crack could initiate in the pile in as little as 6 years, but it may take about 20 years for it to reach the web; however, final failure of the pile may not take place for several decades. The method can also be used as a guide in bridge foundation inspection and in the determination of the remaining life of an existing bridge.