无填充墙基础隔震RC框架在环境激励下的动力特性

对一基础隔震钢筋混凝土框架结构在无填充墙情况下进行了环境激励下的动力测试,重点利用Hilbert-Huang变换与随机减量技术相结合的方法识别了其模态参数,并与随机子空间识别法、有理分式多项式法识别的结果进行了对比。识别结果表明在环境激励下,基础隔震结构的基本周期远小于多遇和罕遇地震工况下设计计算的基本周期;等效黏滞阻尼比很小,近乎于基础固定模型。对隔震层阻尼特性的分析表明,环境激励下可以将基础隔震结构视为经典的比例阻尼系统。进一步以识别的模态参数为基准,采用优化的方法数值反演了环境激励下该结构隔震层的实际水平等效刚度,结果表明其值为多遇地震下计算刚度取值的10.75倍。

Dynamic characteristics of a base-isolated reinforced concrete frame without infill walls under ambient excitation

Ambient vibration test was conducted in a base-isolated reinforced concrete frame building without infill walls.Then modal parameters were identified by the approach using Hilbert-Huang Transform(HHT) and random decrement technique(RDT).And identified results were also compared with the results from stochastic subspace identification(SSI) and rational fraction polynomial(RFP) methods.The identified results show that under ambient excitation,fundamental period of the base-isolated structure is far less than the values under frequently and rarely occurred earthquake level.And the equivalent viscous damping ratio is as low as the value of the base-fixed structure.Discussion on the damping characteristics of isolation layer shows that base-isolated structure can be considered as the classical proportional damping system under ambient excitation.Finally,identified modal parameters were used as the updating benchmark and the actual equivalent horizontal stiffness of isolation layer was inversed numerically using the multi-objective optimization method.The results show that the actual stiffness value is 10.75 times of that in the design case under frequently occurred earthquake level.