浅埋地下结构抗震设计的反应位移法关键问题

Response Displacement Method in Several Key Issues of Shallow Buried Underground Structure Seismic Design

为了解决采用反应位移法进行地下结构抗震设计时工程师所面临的不同计算公式和模型的选取及土体是否需要分层等问题,通过具体算例分析,探讨了影响反应位移法计算精度的几个主要因素,具体包括不同规范中推荐的土体相对位移及剪应力的计算公式、土弹簧刚度的确定方法、分层土体与等效单层土体的差异、荷载-结构模型的选择等.研究结果表明:不同方法确定的土体相对位移、剪应力及土弹簧刚度值相差很大,由此造成的结构内力和变形差异显著,推荐公式应谨慎采用;对存在中柱体系的地下结构,荷载-结构模型应优先采用等代框架模型;采用反应位移法计算时,应严格按照实际分层土体完成土层地震响应分析,避免进行等效均一化处理.

In order to solve problems of selection of different formulas, calculation model as well aswhether need to be decorated in layered soil and so on, in view of actual engineering applications, severalmain factors affecting the calculation accuracy of response displacement method were discussed based onsome specific examples in this paper. The examples include different calculation formulas for relativedisplacement of soil and shear stress recommended by codes, different methods for soil spring stiffnessdetermination, the differences between equivalent single layer soil and actual layered soil, and the choiceof load-structure models. The results show that there are large differences on soil relative displacement,shear stress and soil spring stiffness that calculated by different methods, which can cause remarkablydifferences in structure＇s internal force and deformation. Recommended formula should be carefullyused. In situation of an underground structure with beam-column system, the equivalent planar framemodel should be adopted firstly. Additionally, the actual layered soil should be used to complete the soilseismic response analysis when the response displacement method is employed.