基于Davidenkov骨架曲线模型的修正不规则加卸载准则与等效剪应变算法及其验证

Validation of modified irregular loading-unloading rules based on Davidenkov skeleton curve and its equivalent shear strain algorithm implemented in ABAQUS

非等幅循环荷载作用下,采用"扩展Masing"法则修正应力–应变滞回曲线时,程序的实现过程中需要预留大量的状态变量。针对该问题,提出了Davidenkov本构模型的不规则加卸载修正准则,以代替"扩展Masing"法则中的"上大圈"准则。通过等效剪应变算法的比选,给出了加卸载判据简单且精度更高的等效剪应变算法。基于ABAQUS软件的显式模块,开发了基于不规则加卸载准则的修正Davidenkov本构模型的显式子程序模块,适用于大规模二维和三维场地非线性地震效应分析。选取Mississippi湾500 m深的钻孔作为计算模型,通过与一维场地非线性地震效应分析专业程序Deepsoil计算得到的输入不同强度地震动下的地表峰值加速度、PGA=0.65g的场地地震反应的对比分析,佐证了提出的Davidenkov本构模型不规则加卸载准则与等效剪应变算法的合理性。

Under irregular cyclic loadings, adopting the extended Masing criterion to modify the stress-strain hysteresis curves will bring about the program with a large number of state variables. In this paper, the initial stress-strain skeleton curve is simulated by the Davidenkov model, and the simplified loadIng-reloading rules are proposed instead of the upper boundary rules of the extended Masing criterion. Through comparison, an equivalent strain algorithm with simple unloading judgment standard and higher precision is proposed. Synthesizing computational accuracy and efficiency of large-scale nonlinear seismic site effect analyses, a three-dimensional explicit subroutine of the Davidenkov model with simplified loading-reloading rules is developed in ABAQUS/Explicit module. It is applicable to both two- and three-dimensional seismic site effect analyses. Finally, a two-dimensional numerical simulation for a soil column 500 m thick of Mississippi Embayment is carried out, the peak ground accelerations versus different seismic levels, site seismic responses for Kobe earthquake record of PGA 0.65g are compared with those computed by one-dimensional nonlinear seismic site response analysis program Deepsoil. The results show that the modified irregular loading-unloading rules based on the Davidenkov skeleton curve and the proposed equivalent strain algorithm are rational and valid.