考虑场地土参数随机性和相关性的地震动降维模拟

Dimension reduction simulation of ground motion considering randomness and correlation of site soil parameters

为了考虑场地条件对地震动特性的影响,在非平稳地震动过程的演变功率谱模型中,选择场地土参数作为随机变量,并构造了相应的随机函数形式。建议的随机函数表达不仅能够反映场地土参数的随机性及参数之间的相关性,而且能够直接利用场地土参数的均值、变异系数和相关系数等数字特征来获得其概率分布。同时,利用随机函数的降维思想,建议了基于非确定性谱幅值(NSA)的降维模拟方法,该方法能够同时考虑地震动幅值和相位的随机性,并结合数论方法生成不同场地类别的地震动加速度代表性时程集合。算例表明:场地土参数的随机性和相关性对地震动加速度时程的强度、频率非平稳特性以及频率成分等方面有较大影响。最后,与实测强震动的加速度反应谱以及Fourier幅值谱的比较,进一步验证了模拟方法的工程适用性。

In order to consider effects of site conditions on characteristics of ground motion,in the evolutionary power spectrum model of non-stationary ground motion process,site soil parameters were taken as random variables and the corresponding random function forms were constructed.In the proposed random function expressions,both the randomness of site soil parameters and correlation among them were reflected,and probability distributions of site soil parameters were obtained directly using their digital features,such as,mean value,variation coefficient and correlation coefficient.At the same time,using the idea of random function dimension reduction,a dimension reduction simulation method based on non-deterministic spectral amplitude(NSA)was proposed to consider the randomness of both ground motion amplitude and phase.Based on the number theory method,representative time history sets of ground motion acceleration for different site types were generated.The results of numerical examples showed that randomness and correlation of site soil parameters have larger effects on intensity,frequency non-stationary characteristics and frequency components of ground motion acceleration time-histories.Finally,the dimension reduction simulation results were compared with acceleration response spectrum and Fourier amplitude spectrum of actually measured strong ground motion records to further verify the engineering applicability of the proposed method.