反应位移法抗震设计中地基弹簧系数取值的探讨

Discussion on the Spring Constant of Ground Foundation in the Seismic Design of Underground Structures Using the Response Displacement Method

随着城市轨道交通工程抗震性能越来越受到关注,反应位移法作为一种简捷的抗震设计方法被大量应用于地下结构抗震设计中。地基弹簧系数的确定方法是反应位移法抗震设计中最为重要的因素之一,本文选取试验法、李英民法、MIDAS法和有限元法,结合北京典型地层,对比分析这四种方法地基弹簧系数取值对地下结构的弯矩、轴力和剪力的影响规律。结果表明:(1)在反应位移法计算中,地基弹簧系数取值对结构内力响应具有重要影响,对结构轴力和剪力的影响较大,而对于弯矩的影响相对较小;(2)地基弹簧系数获取方法优选试验法,在无地勘资料情况下,经验公式和有限元法可作为备选方法;(3)综合考虑四种不同地基弹簧系数确定方法对结构内力影响程度,为保证结构设计的安全性,可对试验法下结构内力进行系数修正,修正系数建议值为1.10。

Urban rail engineering faces significant challenges with regard to an earthquake resistant design of underground structures. The response displacement method is a simple method, which is widely used to design such structures. Thus, determining the ground spring constant in theseismic design of underground structures is very important. Four typical determination methodsare introduced： the test method, Li＇s method, the MIDAS method, and the finite element meth-od. Based on the values of the ground spring constant determined through these four methods and considering the local geological conditions in Beijing, response displacement models aobtain the bending moment, axial force, and shear force of the underground structures. The four determination methods are compared on the basis of their respective advantages and disadvantages. The results show that the values of the ground spring constant have a significant influence on the internal force response of underground structures. Moreover, using the response displacement method, we observe that the constant has a greater influence on the axial force aand comparatively lesser influence on the bending moment. The test method is recommended for designers, when geological survey data are not available. The empirical formula and the finite element method can be used as alternative methods. In order to ensure design safety, the internal force of underground structures can be modified by a correction factor of 1.10, considering that the four typical determination methods have an impact on the internal force.