非线性成层地基非平稳动力响应可靠度分析

针对非线性成层地基进行了随机动力有限元分析，求得地基土层的非平稳动力响应及其可靠度。
利用Hardin-Drnevich双曲线模型考虑土层的非线性，通过迭代计算得到土单元的剪切模量与阻尼比。引
入虚拟激励法，将地震加速度非平稳功率谱密度作为虚拟输入，运用有限元方法对土层进行地震响应分析
，得到地基各种动力响应的时变功率谱密度、时变根方差及不同阈值下的时变可靠度。计算结果表明，由
于土层非线性的影响，在非平稳地震输入下，地基系统的自振特性随时间而改变，响应的非平稳特性十分
明显。

Nonstationary probabilistic dynamic response analysis of nonlinear layered soil

The nonstationary dynamic response and reliability of nonlinear soil layer were obtained by stochastic finite element method.Accounting for the nonlinearity of soil,Hardin-Drnevich hyperbolic model was introduced to iteratively evaluate the shear modulus and damping ratio.The evolutionary power spectral density(PSD) of acceleration at the engineering bedrock was dealt with as nonstationary pseudo input.In this frame,the seismic response analysis was carried out via pseudo excitation algorithm combined with finite element method.Results were shown in terms of response evolutionary PSD,variance and reliability with respect to fixed thresholds.The results show that the natural vibration frequencies of the foundation varying with time under nonstationary excitation account for the nonlinearity of the soil.