软场地下两种地震反应分析程序的对比

Comparison of two seismic response analysis programs in soft sites

LSSRLI-1与SHAKE2000是目前国内外等效线性化地震反应分析程序的代表。将LSSRLI-1和SHAKE2000对软土场地进行计算对比,比较加速度峰值、反应谱和剪应变,分析其异同,研究存在的差异及原因,讨论剪应变与加速度峰值和反应谱的相关性,以指导方法和程序的改进。研究结果表明：2个程序计算出的PGA和反应谱结果在某些情况下存在不可忽视的差异,大部分情况下SHAKE2000计算出的PGA要大于LSSRLI-1的结果,在0~3s周期段内大部分情况下SHAKE2000的反应谱大于LSSRLI-1的结果;2个程序计算出的剪应变存在较大差异,LSSRLI-1计算出的的剪应变明显比SHAKE2000大;2个程序计算出的PGA、平均谱值比相对差与剪应变相对差存在相关性,不考虑非线性下,两个程序计算出的地表加速度反应谱基本没有差异,计算地震动的算法应相同;但计算剪应变的结果不同,导致考虑土层非线性的迭代计算结果出现差异。

LSSRLI-1 and SHAKE2000 are typical equivalent linear seismic response analysis programs in domestic and foreign practice. There are soft site cases computed by LSSRLI-1 and SHAKE2000. Their PGA,acceleration response spectrum and shear strain results are analysed and compared. The variation of their results,the origin of the phenomenon and the relationship among relative deviation of shear strain,PGA and response spectrum are discussed,which is used to conduct the development of the programs. Conclusions are summarized below： PGA and response spectrum results are assignably different between the programs in some cases, furthermore SHAKE2000＇s PGA are greater than LSSRLI-1＇s in most cases,SHAKE2000＇s results period ranging from 0s to3 s are greater than corresponding LSSRLI-1＇s by calculating average values; shear strain results are obviously different,and LSSRLI-1＇s results are greater than SHAKE2000＇s; relevance is found between relative deviation of shear strain,PGA,and average response spectrum values. Without soil nonlinear property,response spectrums gotten by the two programs are roughly the same,which suggests that the two programs＇ calculation method of ground motion should be the same. But they are different in results of shear strain,which leads to different results by iteration process considered soil nonlinear property.