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  白建方,董士欣.地震作用下场地有限元建模时底部边界条件的影响[J].震灾防御技术,2018,(1):41-51, DOI:10.11899/zzfy20180104.

地震作用下场地有限元建模时底部边界条件的影响
摘要:    用有限元方法对场地进行地震反应分析时需将半无限域的场地有限化。本文针对底部人工边界的设置,采用滞回阻尼假设,推导了同时包含辐射阻尼和材料阻尼的均质场地地表位移放大系数解析式,进而研究了材料阻尼和辐射阻尼的变化对放大系数的影响。有限元建模时相当于忽略了辐射阻尼,计算误差会随着所分析场地阻抗的增加而逐渐增大,在共振区附近,忽略任一种阻尼的影响,都将显著地高估地表动力反应;远离共振区,阻尼的影响会迅速衰退。本文提出了通过增加场地材料阻尼来弥补所忽略的辐射阻尼的思路,并给出了有限元建模时考虑辐射阻尼后新的材料阻尼的确定方法。
作者单位
白建方 石家庄铁道大学土木工程学院, 石家庄 050043 
董士欣 石家庄铁道大学土木工程学院, 石家庄 050043 
关  键  词:底部人工边界条件  场地地震反应分析  有限元方法  辐射阻尼  材料阻尼
DOI:10.11899/zzfy20180104
基金项目:河北省大型基础设施防灾减灾协同创新中心项目和河北省重点学科建设项目(桥梁与隧道工程)
收稿日期:2017-03-20
作者简介:白建方,男,生于1976年。博士,讲师。主要从事工程系统抗震方面的研究。E-mail:bjf2004@126.com
通讯作者:
The Effect of the Bottom Boundary Condition on Site Finite Element Modeling under Earthquake Load
Abstract:      The actual site is a semi-infinite space and not only on the horizontal direction, but also on the downward are infinitely. In order to build the numerical model for site through direct finite element method, we have to account the artificial boundary conditions first because it is the foundation of how to consider the scope of soil site. In common used method the interface between overlaying bedrock and soil is assumed to be the fixed bottom boundary. In order to find the effect created from this bottom boundary condition, in this paper we performed the theoretical analysis and numerical tests. On this base, we studied the effect of the radiation damping and material damping on the site dynamic response under earthquake load, and it would be possible to decrease the influence of the bottom boundary condition by increases the material damping.
Keywords:  The bottom boundary condition  Site earthquake response analysis  Finite element method  Radiation damping  Material damping
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