考虑桥塔风效应的斜拉桥时域抖振分析

Effect of pylon stochastic wind field on buffeting response of long cable-stayed bridge

大跨度桥梁频域及时域抖振分析中通常仅考虑主梁的脉动风效应。本文根据大跨度斜拉桥结构形式及振动型态的特点,结合自然风的相关特性,对大跨度斜拉桥三维脉动风场进行简化,从而基于谱解法同时模拟了主梁及桥塔的脉动风速场。基于模拟的随机风场对结构风荷载进行时域化,进而建立系统运动控制方程。由于自激力的存在,结构的运动控制方程为非线性方程,本文提出了一种迭代方法来考虑由自激力引起的运动方程的非线性。为考察桥塔脉动风速场的影响,分别进行了考虑桥塔风场和不考虑桥塔风场两种情况下桥梁抖振响应的分析,两种方法的分析结果表明,考虑桥塔风场将显著增大桥塔横桥向抖振响应。

Only wind action of deck is generally taken into account in frequency-domain and time-domain buffeting response analysis for long-span bridge. In this paper, according to the features of the structural style and vibration mode of long span cable-stayed bridge, considering the correlation of the natural wind, overall stochastic wind field of long cable-stayed bridge can be simplified into several one-dimension stochastic wind fields. Due to the simplification, wind fields of deck and pylon can be simulated simultaneously. Based on simulated wind fields, wind load of long cable-stayed bridge can be expressed in time domain form. Further, motion equation of bridge can be built. Due to the existence of self-excited force, the motion equation is nonlinear. An iterative process is presented to solve the nonlinear equation. In order to indicate the pylon wind effect, buffeting response of a cable-stayed bridge is analyzed in two case: with pylon stochastic wind field and without pylon stochastic wind field. The comparisons of two cases show that pylon wind action can remarkably increase buffeting response of pylon in the direction across bridge.