桥梁颤振稳定峡谷效应时域分析

TIME DOMAIN ANALYSIS OF VALLEY EFFECTS ON BRIDGE FLUTTER STABILITY

以地形模型风场测试为手段,测试了山区峡谷桥址的平均风水平分布特性。在风洞试验所得颤振导数的基础上,采用阶跃函数对桥梁断面自激力进行模拟,并对模拟准确性进行了分析与校核,继而推出时域颤振动力有限元分析过程中桥梁断面自激力的递推表达式。在此基础上,最后考虑峡谷桥梁桥面处平均风速的水平分布,对大跨度悬索桥颤振稳定性进行了数值分析。分析结果表明:考虑峡谷平均风速沿加劲梁展向不均匀分布后对桥梁颤振临界风速值有明显的影响,较大幅度地提高了临界风速值。相比之下,按目前我国公路桥梁抗风设计规范取水平向均匀分布风速进行山区峡谷桥梁进行颤振稳定性验算会得到偏于保守的结果。

Resort to the topography model, the horizontal distribution characteristics of mean wind speed in a mountain valley bridge site is tested. Based on the wind-tunnel-tested flutter derivatives, the indicial functions are firstly adopted in the literature to simulate the self-excited aerodynamic forces on bridge girder sections, and, of which the simulation veracity is inspected. Then a recurrence algorithm for self-excited aerodynamic forces on bridge sections is deduced. The aerodynamic forces are indispensable in the dynamic finite element analysis,. Finally, the aerodynamic stability of a long-span valley bridge is investigated in time domain considering the influence of horizontal un-uniform distributed mean wind speed. The numerical results show that the horizontal distribution mode of mean wind speed in valley has an obvious impact on the bridge flutter threshold, which exhibits mainly in enhancing the critical flutter wind speed. In contrast, ignoring the wind horizontal distribution characteristics, as guided by the wind-Resistant code of China highway bridges, may lead to conservative results.