开放系统非线性动力反应分析的一种算法

由于考虑非线性因素影响,动力荷载作用下地下结构反应分析中需将静力反应作为其初始条件．由于透射人工边界、黏性人工边界等局部人工边界条件存在零频限制问题,不能将静力反应的初始条件直接用于这类人工边界条件模拟的动力系统分析中．以往求解静力问题时采用固定边界,再将由此产生的反力作为边界约束力用于动力分析,造成了静、动力分析模型的边界条件不统一．本文将无零频限制的黏弹性人工边界用于动力荷载作用下的地下结构非线性动力反应分析,实现了此类问题在静、动力分析时边界条件的统一性,并以爆炸荷载作用下地下结构的反应分析为例在大型通用显式有限元程序LS-DYNA中实现了这一算法．

An Algorithm of the Non-linear Dynamic Analysis of Open System

Considering the effect of non-linear factors, this article set static response as initial condition for the dynamic response analysis of the underground structures under dynamic loads. Since there is zero frequency restriction on some local artificial boundary conditions such as transmission boundary and viscous boundary etc., the initial condition of static response cannot be directly applied to the dynamic system simulated by those artificial boundary conditions. Fixed boundary used to be applied during the static analysis, and the reactive force on the boundary used to be regarded as the boundary constraint force in the stage of the dynamic analysis. As a result, the boundary conditions of static and dynamic analysis were not uniformed. In this article, the viscous-spring boundary without zero frequency restriction was applied to the non-linear dynamic response analysis of the underground structure under dynamic loads, by which the uniform boundary conditions between static and dynamic analysis were achieved. At last the algorithm was implemented in the explicit FEM program LS-DYNA by the example of dynamic response analysis of the underground structure under explosive loads.