黏弹性人工边界中侧向边界距离选取对计算精度的影响

Influence of lateral boundary distance selection on calculation accuracy in viscoelastic artificial boundary

现有研究成果和震害调查均表明不规则地形对场地地震响应有重要影响,黏弹性人工边界因具有概念清晰,稳定性高,精度好的优点,广泛用于场地地震响应分析。对场地进行地震响应分析时需从无限介质中截取出计算区域,地震波通过黏弹性人工边界进入计算区,同时该边界模拟无限域的弹性恢复和辐射阻尼作用,但通过人工边界向无限域透射的散射波仍会有部分反射进计算区域形成计算误差。本文分别建立半圆凹陷和陡坎地形场地,基于ANSYS结合黏弹性人工边界对比分析侧向边界距离选取对计算精度的影响,结果表明:地震响应分析中,人工边界截断处会引起边界及相邻一定范围内场地地震响应计算误差,应充分考虑人工边界选取距离对精度的影响,设置合理的人工边界选取长度。

The existing research results and seismic damage investigations have demonstrated the significant impact of irregular terrain on the site′s seismic response.Viscoelastic artificial boundary is widely used in the site earthquake response analysis because of its clear concept,high stability and good accuracy.When conducting seismic response analysis on the site,the calculation area needs to be extracted from the infinite medium,and the seismic wave enters the calculation area through viscoelastic artificial boundary,which also simulates elastic recovery and radiation damping in the infinite domain.However,part of the scattered wave transmitted through the artificial boundary to the infinite domain will be still reflected into the calculation area,resulting in calculation errors.In this study,the semicircular concave and steep ridge terrains sites were established,and the impact of lateral boundary distance selection on the calculation accuracy was analyzed by ANSYS in conjunction with the viscoelastic artificial boundary.The results shows that the calculation errors of seismic response occurs in the boundary and adjacent sites within a specific range.Therefore,the selection distance of the artificial boundary influence on accuracy should be comprehensively considered,and an appropriate length of artificial boundary selection should be established.