近海大气环境下锈蚀RC框架梁恢复力模型研究

A RESTORING FORCE MODEL OF CORRODED REINFORCED CONCRETE FRAME BEAMS IN OFFSHORE ATMOSPHERIC ENVIRONMENT

为了研究近海大气环境下锈蚀RC框架梁的抗震性能,对8榀经受不同盐雾腐蚀循环作用的RC框架梁进行了低周反复加载试验,分析RC框架梁的滞回特性。基于试验结果,得到了带有负刚度段的三折线骨架曲线,并根据完好构件恢复力模型特征参数,得到了考虑钢筋锈蚀率和配箍率的锈蚀RC框架梁骨架曲线特征点计算公式。采用回归分析法,得到基于滞回耗能的循环退化指数,通过循环退化指数建立可综合考虑构件的捏拢效应、强度退化、卸载刚度退化、硬化刚度退化和再加载刚度加速退化的锈蚀RC框架梁恢复力模型。研究表明:随着钢筋锈蚀程度的增加,锈蚀RC框架梁的抗震性能劣化较明显,滞回耗能逐渐降低;配箍率对锈蚀RC框架梁恢复力特性的影响与未锈蚀RC框架梁相似;所建立的恢复力模型能够较好的描述锈蚀RC框架梁的滞回特性,可为该类结构的弹塑性时程分析提供理论参考。

To study the seismic behavior of corroded Reinforced Concrete (RC) frame beams in offshore atmosphere, the hysteretic behavior of 8 RC frame beams were investigated experimentally, which have been damaged by the salt spray corrosion cycles under low cyclic reversed loading. Based on the test results, a trilinear skeleton curve model with negative stiffness of frame beams was established. According to the characteristic parameters of the intact member's restoring force model, the formula of the characteristic points of the skeleton curve of RC frame beams with corrosion was obtained, which considered the corrosion rate and stirrup ratio. The cyclic degradation indexes of RC frame beams based on hysteresis energy dissipation was obtained through regressive analysis. Subsequently, the restoring force model of corroded RC frame beams was established, which considered the pinch-in effect, strength degradation, unloading stiffness degradation, hardening stiffness degradation and reloading stiffness accelerates degradation. The results show that the seismic performance of RC frame beams deteriorates obviously with the increase of corrosion degree, and the hysteretic energy consumption decreases gradually. The influence of stirrup ratio on the restoring force of RC frame beams is similar to the un-corroded frame beams. The restoring force model can describe the hysteretic behavior of corroded RC frame beams well. The study results will shed light on the theoretical research about the elastic-plastic dynamic analysis of RC structures.