底部框架双功能减震结构减震参数的取值分析

摘要

采用随机振动理论,对底部框架双功能减震结构进行地震激励下的位移响应方差分析,探究该结构减震参数的合理取值.本文在底部框架中设置粘滞阻尼器,在上部砌体底部设置隔震装置构成底部框架双功能减震结构.本文建立振动方程,利用随机振动理论,导出下部框架和上部砌体结构的位移响应方差,通过非线性数学规划法对该位移响应方差最小值进行优化分析,给出了底部框架等效阻尼比、隔震层阻尼比、上下部结构自振频率比及质量比对上下部结构位移响应方差的影响规律.结果表明:底部框架等效阻尼比取值应在0.30左右,隔震层阻尼比取值宜在0.20～0.40之间,上下结构自振频率比取值不宜超过1.0,且上下结构质量比超过一定范围,增大质量比,位移响应方差越大.分析表明,底部框架双功能减震结构应综合考虑各减震参数之间的相互影响,对各减震参数宜优化取值.%Based on random vibration theory,the displacement response variance is analyzed for the bottom frame double-function damping structure under earthquake excitation,and the reasonable value of structural damping parameters is explored.In this paper,the bottom frame double-function damping structure is presented,which consists of the viscous dampers set in the bottom of frame and the vibration isolation device set at the bottom of upper masonry.Vibration equation is established in the paper,the displacement response variance of bottom frame and upper masonry structure is derived by random vibration theory,and the minimum displacement response variance is optimized by nonlinear mathematical programming method.The quivalent damp ratio of bottom frame,the isolation layer damp ratio,the natural frequency ratio and mass ratio of top and bottom structure on displacement response variance of the bottom frame and the upper masonry structure are studied.The results indicate that the quivalent damp ratio of bottom frame should be greater than 0.2,the isolation layer damping ratio should be between 0.2 and 0.4,the optimal frequency ratio is less than 1.0,and when the mass ratio beyond a certain range,the displacement response variance may increase with the mass ratio increasing.Therefore,the optimization value of damping parameters should comprehensively consider the mutual effect of all parameters of the structure.