隔震结构地震波选择方法研究

隔震结构的设计一般是采用时程分析算法进行的,故选择合适的地震波十分重要。而目前设计人员往往依据隔震前模型进行隔震设计,存在一定的不合理性。本文依据隔震前和隔震后两种不同的选波模型和对地震波反应谱控制频段的不同提出三种选波方案:方案一为对所选地震动的加速度反应谱在场地特征周期Tg附近的平台段和隔震前结构基本周期T1a所在下降段的控制;方案二为对在Tg附近的平台段和隔震后结构基本周期T1b所在下降段的控制;方案三为对所选地震动的加速度反应谱在Tg附近的平台段和隔震前、后两结构基本周期段的分别控制。通过对某五层混凝土框架隔震结构分别输入三种方案所选的20条地震动记录,对比隔震结构的水平向减震系数的离散性,分析罕遇地震作用下支座位移的合理性,证明方案三可以取得最优的计算结果,并提出一种基于规范设计反应谱不同频段的三频段控制选波方法。此外选取5个不同结构形式的工程算例验证三频段控制选波方法对于一般结构的适用性。

Discussion of Seismic Waves Selection Method for Isolation Structures

Most isolation structure designs are based on a time-history analysis, which is greatly affected by earthquake waves. At present, the non-isolated model is most often used in isolation structure design, but this contains certain irrationalities. In this paper, three types of schemes based on two different models (isolated and non-isolated models) are proposed to select earthquake waves, together with different control frequency ranges of seismic response spectrum. Twenty seismic waves are selected in accordance with the three schemes, and these are input in a five-story base-isolated concrete frame structure. The discreteness of horizontal seismic reduction coefficients of the structure is then compared. Furthermore, displacements of the isolated bearing of the structure under a rare earthquake are analyzed. Results show that the third scheme provides optimal calculation results. A three-frequency range method for selecting waves based on different frequency ranges of code design response spectrum is then proposed, and five engineering examples with different structures are selected to verify the applicability of the method. Results show that the method is suitable for use with common structures.