基于规范谱的隔震结构非弹性位移设计谱研究

Study on the Inelastic Displacement Design Spectrum ofan Isolated Structure Based on the Code Spectrum

摘要:

随着基于性能抗震设计理论研究的兴起，位移反应谱的研究逐渐受到重视。对于具有长周期特性的隔震结构，其位移响应相对于加速度响应更加显著，有必要对隔震结构的位移响应进行研究。选取特定震源机制、场地条件、震中距和震级的60条地震记录作为外部激励，利用MATLAB编程并计算得到隔震结构的位移反应谱，通过与规范反应谱进行对比分析，探讨利用现行规范谱来预测隔震结构位移需求时存在的一些问题。考虑隔震支座力学参数、地震动特性等因素对位移反应谱的影响，采用标准化和平均化的方式研究位移反应谱的特征，以Eurocode8规范给出的弹性位移反应谱为基础，通过数值拟合方法建立隔震结构非弹性位移设计谱，用于预测隔震层的最大位移需求，快速确定支座类型，极大简化隔震结构设计流程。

Abstract:

With the development of performance-based design methodologies, the research of displacement response spectra is gradually becoming more important. For the isolated structure with long period, the displacement response is more significant than that of the acceleration response, which makes it necessary to study the displacement response spectra. According to the rule of the specific earthquake mechanism, site conditions, epicentral distance, and magnitude, 60 earthquake records are selected as the external incentive. MATLAB software is used to script a program for the displacement response spectra; the result of displacement response spectra is derived from the program and compared with the spectra given by the codes, and some inherent problems are discussed when the spectra given by the codes is used to predict the displacement demand on the isolated structure. Research results show that for the inelastic displacement response spectra of the isolated structure, including the ascending segment, the stable segment, and the horizontal segment four stage with the prolonging of the natural vibration period, the displacement response spectra derived from the spectra given by the Chinese seismic code is significantly different in spectral shape and amplitude. The displacement response spectra proposed by Eurocode8 has similar shape to the isolated structure, which can better describe the change trend, but the peak value of the displacement spectra is larger than the actual calculated value. So, the characteristics of the displacement response spectral shapes and amplitudes are thoroughly researched according to the result calculated by MATLAB, the influence of factors like the yield displacement (X_y) and yield stiffness ratio (α) of the seismic isolation bearing, ground motion intensity parameters on the displacement response spectra are considered. Based on the obtained results, an updated formulation for the inelastic displacement design spectrum of an isolated structure is proposed, which can be used to predict the displacement demand of the isolation layer and to determine the type of bearing; thus, simplifying the design process.