紊流中大跨桥梁的扭转发散特性  

TORSIONAL DIVERGENCE CHARACTERISTICS OF LONG SPAN BRIDGE IN TURBULENCE

作　　者：张志田[1] 陈政清[1] 葛耀君[2] 华旭刚[1] 陈立方 

机构地区：[1]湖南大学风工程试验研究中心,长沙410082 [2]同济大学土木工程防灾国家重点实验室,上海200092 [3]湖北路桥集团五公司,武汉430056

出　　处：《工程力学》2010年第2期108-116,共9页Engineering Mechanics

基　　金：国家自然科学基金项目(50708036)

摘　　要：大跨度缆索承重桥梁的静风失稳,特别是导致桥梁突然破坏的扭转发散是桥梁工程师在设计阶段十分关注的问题,静风稳定性分析的传统方法是考虑均匀流静风荷载,采用静力有限元迭代法来求解。然而,自然界大气边界层中的气流总是紊流而非均匀流,而紊流对扭转发散的影响却需要深入的研究。为考虑紊流的影响,该文采用动力有限元方法在时域范围内分析桥梁的静风稳定性,并提出相应的风荷载表达式。应用该文提出的方法对目前国内最大跨度桥梁的静风稳定性进行了分析。数值分析结果表明:桥梁的扭转发散特性在均匀流与紊流场下的差异很大。这种差异主要表现在结构的发散形式不一样,在均匀流中加劲梁扭转发散表现为突变扭转位移而在紊流场中则表现为有巨大扭转峰值的随机振动;此外,扭转发散的临界风速也有所差异,紊流明显地降低了扭转发散临界风速。参数分析表明:紊流强度与脉动风场空间相关性也对桥梁的静风稳定性能有着重要的影响。Aerostatic stability of long-span cable supported bridges, especially the torsional divergence which may lead to abrupt bridge failure, are much concerned by bridge engineers during the design stage. The traditional method dealing with such problems usually adopts an iterative static finite element procedure considering the aerostatic loadings due to smooth flow only. However, airflow in nature bound layer is always turbulent and the effects of atmospheric turbulence on bridge torsional divergence need an in-depth investigation. To account for the effects of turbulence on torsional divergence, this paper adopted dynamic finite element method and performed bridge aerostatic stability analysis in time domain. The appropriate wind load expressions were also presented. Then the aerostatic stability of the longest bridge in China was investigated by the approach presented in this paper. Numerical results show that bridge torsional divergence in turbulent flow is much different from that in smooth flow. The primary difference lies in the form of torsional divergence, which manifests as an abrupt twist deformation of the girder in smooth flow, but an unstable stochastic vibration with large peak values in turbulent flow. The second difference lies in the critical divergence airspeed values. Numerical results show that turbulence decreases the critical divergence airspeed obviously, and, turbulence intensity and the spatial correlation of wind fluctuations also play an important role on that.

关 键 词：紊流 大跨度 桥梁 扭转发散 静风稳定 

分 类 号：TU318[建筑科学—结构工程]