黏滞阻尼器-基础隔震混合体系优化研究

Optimization research for base-isolated structures with fluid viscous dampers

针对隔震层设置黏滞阻尼器的基础隔震结构,提出了非支配排序遗传算法-Ⅱ(NSGA-Ⅱ)的黏滞阻尼器的参数多目标优化方法。采用Bouc-Wen模型模拟隔震层的力-变形行为,建立受控结构运动方程,并进行非线性时程分析,选用隔震层位移及上部结构顶部相对隔震层位移为优化目标,采用NSGA-Ⅱ遗传算法优化得Pareto最优前沿解集。以某六层基础隔震结构为例进行数值分析,通过分析隔震层振动响应的快速傅里叶变换(FFT)谱及反应谱,以及通过调整优化目标的约束条件及参数的优化范围,利用NSGA-Ⅱ算法获得了较为集中的阻尼器参数分布,然后通过其它地震波验证了黏滞阻尼器的减震效果。结果表明,优化所得阻尼器能有效减少了隔震层的位移;当优化所得阻尼器对上部结构地震响应不利时,可通过降低阻尼器的减震效果使上部结构地震响应控制在合理范围内;不同地震波作用下阻尼器减震效果存在差异,在第一周期范围内,当隔震层的激励频率趋向低频时,阻尼器对隔震层位移控制效果越好;阻尼器减震效果与隔震层的附加阻尼有关,提供过大的附加阻尼比对上部结构较高阶动力反应不利;设计者基于隔震层位移控制的阀值及缩小的阻尼器参数优化范围,可获得应用于实际工程的阻尼器参数。

For the base-isolated structure with fluid viscous dampers in isolation layer,a parametric multi-objective optimization method of fluid viscous damper using non-dominated sorting genetic algorithm(NSGA-Ⅱ)was proposed.Bouc-Wen model was applied to simulate the isolation layer’s force-deformation behavior.The motion equation was established for time-history analysis.The total displacement of the isolation layer and superstructure were selected as the optimization objective.The Pareto optimal front can be gained through algorithm.A six-storey base-isolated structure was selected as an example of numerical analysis.The vibration responses of the isolation layer were selected for FFT spectrum analysis and response spectrum analysis.By adjusting the constraint of optimization target and the optimization range of the parameters,NSGA-Ⅱwas also used to obtain a more concentrated parameter distribution,and the effectiveness of the damper was verified by other earthquake.The results show that the optimal dampers can effectively reduce the displacement of isolation layer;for some earthquake,the optimal dampers may be detrimental to the seismic response of the superstructure.However,the seismic response of the superstructure can be kept in acceptable range by reducing the effectiveness of fluid viscous damper;the damper effectiveness depends on the type of earthquake.When the main excitation frequency of the isolation layer tends to be lower in the range of first mode frequency,the damper has better effectiveness in controlling the displacement of isolation layer;the damper effectiveness is correlated with the acceptable supplemental damping of isolation layer;the excessive supplemental damping is not favorable to the dynamic response of the superstructure;according to the threshold of the displacement of the isolation layer and the reduced optimal range of the damper parameters,the damper parameters that can be applied to actual projects could be obtained.