环境激励下底层柱顶隔震结构动力特性测试分析

TESTING AND ANALYSIS OF DYNAMIC CHARACTERISTICS OF THE ISOLATION STRUCTURE FOR A FIRST-STORY COLUMN TOP UNDER AMBIENT EXCITATION

通过对采用底层柱顶隔震技术的六层框架结构在环境激励条件下的振动测试,运用基于传递率的工作模态参数识别方法,识别了结构的模态频率(周期)、振型和模态阻尼比,并对隔震结构和非隔震结构进行数值计算,对比结果表明:环境激励条件下,底层柱顶隔震结构自振周期的理论值与实测值较为接近,其基本周期远小于设计计算设防刻度地震下的基本周期;与非隔震结构相比,底层柱顶隔震结构的基本周期较小,二者存在一定的差距,说明隔震结构在微幅振动下隔震层初始刚度较大,可以保证隔震结构正常使用;等效黏滞阻尼比较小,与非隔震结构的阻尼比相当,说明环境激励条件下底层柱顶隔震结构并不具备非比例阻尼特性,可以视作经典的比例阻尼系统。

Ambient vibration tests were conducted on a six-story frame-structure,to which first-story column top isolation technology was applied. Modal frequencies（ period）,mode shapes and modal damping ratios were identified using operational modality parameter identification method based on transmissibility. Finite element calculation and analysis of isolated structure and non-isolated structure were conducted. The comparative results showed that under ambient excitation,the measured value of first-story isolation structure natural period was closed to the theoretical value,whose the fundamental period was much less than the value under seismic fortification intensity. A first-story isolation structure had shorter period than non-isolated structure. There was a certain difference between the two structures. The initial stiffness of isolation layer was large in a slight vibration. The isolation structure with sufficient stability,can ensure its normal use. The equivalent viscous damping ratio was low and about the same as the value of a non-isolated structure,so a first-story column top isolation structure could be considered as the classical proportional damping system under ambient excitation.