近断层地震作用下斜拉桥黏滞阻尼器参数简化设计方法

Simplified parameter design method of viscous dampers for cable-stayed bridge under near-fault ground motions

黏滞阻尼器是漂浮体系斜拉桥常用的减震耗能装置,但传统的阻尼器参数设计需要通过反复的非线性有限元时程计算来确定,这种方法不够简便有效。本文根据近断层地震的脉冲特点以及斜拉桥动力特性,通过建立斜拉桥的双质点模型的运动微分方程,推导出近断层脉冲作用下的动力反应计算公式;并基于等效线性化方法,得到非线性黏滞阻尼器参数与等效阻尼比的关系,从而利用主梁目标位移反向确定所需设置的黏滞阻尼器参数;最后通过一座斜拉桥实例验证本文方法的正确性,并提出了黏滞阻尼器参数设计简化方法的流程。

Viscous damper is one of the most widely used passive energy dissipation devices for cable-stayed bridge with floating system, however, the conventional parameter design method, which is far from efficiency and convenience, resorts to repeated nonlinear time history analysis. Therefore, based on the ＂pulse＂ characteristics of near-fauh ground motions and the dynamic characteristics of cable-stayed bridge, the kinematic differential equations for a simplified two- mass model of cable-stayed bridge are established, and the calculation formulas for the dynamic response of girder displacement under the impact of near-fauh pulse are derived. By using the equivalent linearization method, the relationship of nonlinear viscous damper parameters and equivalent damping ratio is achieved. Hence, the design parameters of viscous damper can be reversely determined by making use of the objective girder displacement of cable- stayed bridge. Finally, this simplified method is validated by a realistic case of cable-stayed bridge, and the flowchart for the simplified design method of viscous damper is also described.