基于结构响应极值前四阶矩的桥墩抗震可靠度

为研究桥墩非线性地震响应下的抗震可靠度,引入随机函数-谱表示模型与高阶矩法,提出了基于结构响应极值前四阶矩的桥墩抗震可靠度分析方法。考虑三线型恢复力模型,建立了桥墩的单墩模型;利用随机函数-谱表示模型生成非平稳地震加速度时程样本并对桥墩进行非线性时程分析,在此基础上,建立了结构响应极值前四阶矩(均值,标准差,偏度和峰度)的计算框架;最后,考虑桥墩位移界限,给出了桥墩位移的功能函数,进而利用高阶矩法计算桥墩抗震可靠指标。通过对桥墩结构分析,验证了该方法的高效性与精确性;计算结果表明:与Monte Carlo模拟结果相比,该方法计算的前四阶矩、抗震可靠指标(失效概率)的最大相对误差分别为0.28%,1.92%(4.92%),该方法为桥墩抗震可靠度评估提供了一种有效的途径。

Aseismic reliability of bridge piers based on first four moments of extreme structural responses

In order to study aseismic reliability of bridge piers under their non-linear seismic responses, the random function-spectrum representation model and high-order moment method were introduced to propose a bridge pier’s aseismic reliability analysis approach based on first four moments of extreme structural responses. Firstly, a three-line restoring force model was considered to establish a single column model of bridge pier. Secondly, the random function-spectrum representation model was used to generate non-stationary seismic acceleration time-history samples, and non-linear time history analysis was conducted for the bridge pier’s structural responses. Then, the calculation framework for first four moments including mean, standard deviation, skewness and kurtosis of extreme structural responses was established. Finally, the pier displacement limit was considered to deduce the pier displacement’s performance function, and the high-order moment method was used to calculate the bridge pier’s aseismic reliability index. Through the bridge pier’s structural analysis, the effectiveness and precision of the proposed method were verified. The results showed that compared with the simulation results using Monte Carlo method, the maximum relative errors of first four moments, aseismic reliability index and failure probability calculated using the proposed method are 0.28%, 1.92% and 4.92%, respectively; the proposed method provides an effective way for evaluating aseismic reliability of bridge piers.