Prediction of ultralow cycle fatigue damage of thin-walled steel bridge piers

Abstract

Ultralow cycle fatigue (ULCF) failure was first observed on steel bridge piers in the Kobe earthquake, and the ultimate strength and ductility evaluation formulas of thin-walled steel bridge piers were established. In this study, parametric analysis of steel piers was carried out to study the influence of the structural parameters on the ULCF damage evolution. The evolution of the ULCF damage of the base metal, the deposited metal, and the heat-affected zones was studied based on two types of steel piers with hollow box and pipe sections. Then, practical formulas to predict the ULCF damage level of steel piers under cyclic loading were proposed. Finally, the proposed formulas were validated by comparisons with the experimental results. The results show that the heat-affected zone is more vulnerable to ULCF failure than the base metal and the deposited metal. Moreover, the practical formulas to predict the ULCF damage index of the steel piers under cyclic loading were proposed, and the formulas effectively predicted the ULCF crack of the steel piers.