水平土层地震反应分析考虑频率相关性的等效线性化方法

工程场地非线性地震反应分析中,等效线性化方法因原理相对简单、参数获取方便而得到广泛应用。但这种方法算得的地面最大加速度值以及高频段的频响放大倍率与实测结果有较大差异。首先对比分析了几种考虑频率相关性等效线性化方法的原理,对频率相关性的实质进行了初步探讨。在分析具有竖向钻孔地震记录的场地土层应变频谱特征基础上,采用谱平滑化方法进行标准化应变谱曲线拟合,从而得到考虑频率相关性的新方法。通过改造DYNEQ程序得到各种方法的计算程序,并用新方法与其他方法分析了有竖向钻孔地震记录场地的非线性地震反应。分析结果表明:考虑频率相关性后的计算方法比传统方法均有所改善,本文新方法表现出良好的适用性。

An equivalent linear method considering frequency-dependent soil properties for seismic response analysis

Equivalent linear method was widely used in the seismic response analysis of soil deposits because of its simplicity in preparing the input data and the stability of numerical calculation, but some problems, such as underestimating the Fourier spectrum amplification ratio at high frequency and overestimating the peak ground accelerations, would appear in its practical application. The theoretical background of equivalent linear methods considering frequency-dependent soil properties was shown. Downhole array records were used and fitting lines of the strain spectra were analyzed. A new method considering frequency-dependent soil moduli and damping was proposed using the new spectral fitting line of the strain. Based on the computer code DYNEQ and the above-mentioned theories, two computer programs were compliled. Three sites were analyzed using these programs and the results were compared with the downhole array records. The prediction with the methods considering frequency dependent soil properties was better than that of the original equivalent linear method SHAKE, and they were different from each other in the analysis details. The results obtained by the proposed method agreed well with the downhole array records.