剪切质点系法的改进及在层状地基中的应用

Improvement of Shear Particle System Method and Application on Layered Foundation

传统的剪切质点系法只能考虑土体的材料阻尼的影响,无法考虑辐射阻尼的影响,分析层状地基的地震反应往往偏大。本文对传统的剪切质点系法进行了改进,在地基底部增加粘性边界以替代固定边界,使用瑞利阻尼估计土体的材料阻尼,并采用直接积分法中的Wilson-θ法以加快求解效率。改进后的剪切质点法计算层状地基地震反应时可以同时考虑辐射阻尼和土体的材料阻尼的影响,结果更合理。以某多层地基为例,通过与理论解的对比验证了改进的剪切质点法可准确计算地震波的传播过程,模拟辐射阻尼效应。计算结果表明,同时考虑辐射阻尼和土体阻尼影响时所得地表位移比仅考虑其中一种阻尼时要小25%~35%。

Sheer particle system method only the material damping of soil can be taken into ac- count, while the radiation damping can＇t be taken into account, that exaggeratedly estimates the seismic response of layered foundation. This paper improved the sheer particle system by repla- cing the fix boundary by a viscous boundary, using Rayleigh damping model to consider the soil damping and using Wilson-theta method to accelerate calculation speed. The improved sheer mass particle method can consider the radiation damping and material damping at the same time in seismic response analysis which is more comprehensive. This improvements is proved to be ef- fective by comparing the calculated result with the imaginary layered foundation. The compara- tive analysis indicates that the maximum displacement of foundation surface considering the ma- terial damping and radiation damping at the same time is about 25% and 35% smaller than only considering one type of damping.