分析三维土-结构动力相互作用体系等效输入的时域显式有限元法

The explicit finite element method in time domain for analysis of equivalent input of three-dimensional dynamic SSI system

基于直接法中分析三维土-结构相互作用问题的两步法思想,提出关键性第一步等效输入计算的时域简化算法。本方法在采用集中质量显式有限单元法结合显式人工边界的同时,借鉴子结构法中刚性基础假设及动力相互作用的概念,简化三维土-结构相互作用体系动力计算过程。和其他同类方法相比,本方法完全采用时域显式递推的过程,计算效率较高,计算量少;等效输入的获得,可使土-结构复杂体系的动力分析等效为常规的上部结构动力反应计算,时域算法较常用的频域法在土体非线性方面存在更大潜力。本文还通过典型的三维土-结构模型的建立,与相应的参考解相比,验证本文提出的计算方法的有效性和计算精度,并初步探讨土-结构动力相互作用体系的一些基本规律。

For decreasing the computation cost,a new explicit numerical simplified procedure in time domain is proposed for the rigid boundary equivalent input computation for three-dimension dynamic SSI system in this paper.Based on the lumped-mass explicit finite element procedure with a local transmitting artificial boundary in time domain,the rigid foundation assumption and the dynamic interaction relationship usually used in substructure method are adopted to simplify the computation procedure.This method has advantages in computational feasibility and the applicability in engineering when the explicit finite element and step-by-step integration scheme is adopted.The lump-beam model for upper structure and the rigid foundation assumption can make the cost of computation equal to that of free field computation.Compared to the computation procedure in frequency domain,the computation in time can be advanced in deal with the nonlinear soil body.In addition,the equivalent input of upper structure obtained by the simplified procedure make the complex SSI system analysis equal to the common upper structure dynamic analysis.To illustrate the efficacy and reliability of the procedure,several three-dimension SSI numerical examples are presented.The computational predictions based on the assumption of presented procedures are in good agreement to the reference solutions.At the same time,numerical examples are also used to study for the influence on structural seismic response by the different seismic input cases usually used in design.