Low-Cycle Fatigue Damage of Circular Concrete-Filled-Tube Columns

摘要

Under seismic actions, the induced damage in critical regions of a concrete-filled steel tube (CFT) column could be attributed to cumulative damage of the steel tube caused by repeated cyclic loading in the post-yield strain range. An experimental study was undertaken to develop an analytical model of cumulative damage for circular CFT columns subjected to cyclic loading. The low-cycle fatigue behavior of CFT columns was investigated and a relationship between fatigue life and normalized displacement amplitude was established for typical controlling parameters. A total of 12 large-scale model column specimens, representing two types of circular CFT columns with different steel tube diameter-to-thickness ratios were tested under quasistatic loading with either constant drift amplitude or standard cyclic loading histories with increasing peak drift displacement. Test results indicate that the low cycle fatigue behavior of CFT columns depends on the thickness of the steel tube. Fatigue life expressions useful for application in damage-based seismic design are developed and used to predict the damage index for additional CFT columns based on experimental data reported in the literature.