索网结构非线性地震反应分析实用方法

采用现有方法分析索网结构非线性动力反应时,仅能对矩形平面索网结构建立等效单自由度(ESDF)模型,地震作用下,此类结构的响应只能采用时程法进行计算。基于结构整体刚度参数的概念,结合模态推覆分析方法,建立了任意形状索网结构的非线性ESDF模型,该模型刚度特性与Duffing系统相同。采用能量平衡法,导出了索网结构非线性ESDF体系的等效线性刚度ke与位移反应d的关系;结合ESDF体系的等效质量,将加速度-周期(a-T)格式的设计反应谱变换为刚度-位移(k-d)格式;与ke-d关系式联立求解得出ESDF体系的非线性地震反应。该方法在线性设计反应谱的基础上,合理考虑了索网结构的非线性刚化效应。数值算例表明,相对于线性振型叠加反应谱法,该方法具有更好的适用性。

A Practical Approach for the Nonlinear Seismic Response Analysis of Cable Net Structures

When the existing procedures are adopted in analyzing the nonlinear dynamic responses of cable net structures,the nonlinear equivalent single degree of freedom(ESDF)models can only be used for those rectangular-shaped cable nets.Meanwhile,their nonlinear seismic responses can only be computed through the time-history analysis method.Based on the concept of the overall structural stiffness and the process of modal pushover analysis(MPA),this paper provides a method for building nonlinear ESDF models for cable nets with any geometry.The stiffness of nonlinear ESDF models is the same as that of the Duffing systems.According to the energy balance method,the relationship between the equivalent stiffness keand displacement response dfor a nonlinear ESDF system of a cable net structure is derived.Considering the equivalent mass of the ESDF system,the acceleration-period formed design response spectra is transformed into a stiffness-displacement form.Then the transformed spectra is used in accordance with the ke-d relationships for calculating the displacement responses of ESDF systems.Numerical examples demonstrate that the proposed method is more realistic than the linear modal superposition method,because the former can reasonably consider the nonlinear stiffing effect of cable net structures based on the design response spectra.