基于修正阻尼的土体非线性模型及其在Abaqus中的实现

A dynamic nonlinear constitutive model for soil based on modified damping and its implementation in Abaqus

地震等随机循环荷载作用时,常需定义较为复杂的加卸载准则(如扩展Masing准则)来描述土体应力-应变滞回曲线,导致求解过程中需预留大量的状态变量,不便于编程实现;同时,现有Masing模型及其改进模型大多仅对动剪切模量曲线进行拟合,还鲜有考虑对阻尼比曲线的拟合。针对以上两个问题,构建了基于修正阻尼的不规则加卸载准则。该准则克服了上大圈准则需要记忆所有转向点的问题,只需要记忆当前转向点和历史最值,记忆量大大减小;同时该准则能同时考虑动剪切模量和阻尼比曲线,达到了修正阻尼比的目的。基于Matasovic骨架曲线,结合提出的加卸载准则,提出了土体非线性模型并将其开发于Abaqus软件中,通过求解Mississippi湾场地地震反应,并与Deepsoil软件和Davidenkov-Chen-Zhao(DCZ)模型计算得到的场地地震反应结果进行对比分析,验证了所提不规则加卸载准则的正确性。同时,对日本KiK-net强震台网的KSRH10场地进行了地震反应分析,并与加速度时程记录及其谱加速度进行比较,验证了所提模型的适用性。

The existing Masing-type nonlinear soil constitutive models encounter the problem of relatively complex loading-unloading rules(eg,the"extended Masing"rule)to describe the soil stress-strain hysteresis curve under the irregular cyclic loadings such as earthquakes.It will lead to a large number of state variables during the solution,which is inconvenient to be implemented.At the same time,the existing(improved)models primarily match the shear modulus reduction curves with the damping ratio curves rarely being matched.In this paper,to overcome the above problems,a new irregular loading-unloading rule is proposed based on modified damping.The rule overcomes the"upper boundary rules",and only the current reversal point and historical maximum(minimum)point need to be stored,which greatly reduces memory.Meanwhile,it accounts for the effect of soil shear modulus and the damping ratio curve simultaneously to modify damping ratio.Then,a new nonlinear constitutive model is proposed and implemented into the Abaqus software based on the Matasovic back-bone curve and the proposed loading-unloading rule.The correctness of the proposed loading-unloading rule is verified by comparing numerical results of the site seismic response of Mississippi Bay with the results calculated by the Deepsoil software where the Davidenkov Chen Zhao(DCZ)model is adopted.To further validate the practical applicability of the proposed model,the seismic response analysis of KSRH10 site of Japan KiK-net is conducted and compared with the record of acceleration time history and spectral acceleration.