基于OpenSEES数值模拟的工字形截面支撑低周疲劳性能研究

In order to study the low-cycle fatigue behavior of I-shaped steel bracing members, numerical simulations of 18 Q235 and 21 ST12 welded steel braces under constant amplitude cyclic axial displacement were carried out by using OpenSEES. Based on these results, which were consistent with the test ones, representative strain modified by geometric parameters(including slenderness ratio, width-to-thickness ratio, height-to-thickness ratio and yield stress) of braces was proposed as a new control parameter to predict low-cycle fatigue life of bracing members. And its corresponding formula for modification and prediction was given. It is shown that the predicted low-cycle fatigue lives are basically located within a safe scatter band of 1.5 according to the logarithmic linear relationship between this strain and the low-cycle fatigue life. For the life prediction of brace under variable amplitude loading, the Miner linear damage theory was used to conduct damage statistics of 39 bracing members, with the crack initiation life as the termination point, and the recommended allowable damage value was given as the corresponding damage value of the predicted life. Then a simulation of five single diagonal braced frame tests was conducted. The predicted lives of all these specimens are close to crack initiation life of tests, which prove that it can give the brace a more conservative evaluation of the low-cycle fatigue behavior, and the section damage distribution is consistent with the experimental failure mode. All the results demonstrate the accuracy and efficiency of the method of numerical simulation and low-cycle fatigue life prediction, which can provide a reference for the research on the low-cycle fatigue performance of high-rise braced frames.