典型钢混Π型主梁断面的涡振特性及其响应预测研究

Study on Vortex-Induced Vibration Characteristics of a Typical Steel-ConcreteΠGirder and Its Response Prediction

为研究Π型主梁断面的涡振特性及预测其响应,以某大跨钢混Π型梁斜拉桥为背景,在风洞中测试了不同质量与不同阻尼比的主梁涡振特性,通过自由振动试验识别了主梁的动力参数,并提取了不同风速下主梁的幅变阻尼比及幅变频率.进一步,基于幅变气动导数建立了主梁的涡激力模型,同时通过涡激力模型实现了不同阻尼比下主梁涡振振幅及涡振区间的预测.研究结果表明,钢混Π型主梁在不同风速范围内竖向模态参数呈现不同的发展规律,可划分为5个风速区间;基于Scanlan自激力模型建立了只包含H_(1)和H_(4)两个气动导数的涡激力模型,通过与风洞试验的涡振振幅和涡振区间结果进行对比,验证了涡激力模型及其涡振气动导数方法的正确性,同时与不同阻尼比下的风洞试验结果对比,验证了该涡激力模型具有普适性.研究结论可为Π型主梁断面的涡振机理与涡激力模型的建立提供参考.

In order to study the vortex-induced vibration characteristics of theΠ-shaped girder section and predict its response,taking a long-span steel-concreteΠ-shaped girder cable-stayed bridge as the background,the vortex-induced vibration characteristics of the girder with different mass and damping ratios were tested in the wind tunnel.The dynamic parameters of the girder were identified by free vibration test,and the amplitude-varying damping ratio and amplitude-varying frequency of the girder under different wind speeds were extracted.Furthermore,the vortex-induced force model of the main beam is established based on the amplitude-varying aerodynamic derivative.At the same time,the vortex-induced force model is used to predict the vortex-induced vibration amplitude and vortex-induced vibration interval of the main beam under different damping ratios.The results show that the vertical modal parameters of the steel-concreteΠ-shaped girder show different development rules in different wind speed ranges,which can be divided into five wind speed ranges.Based on the Scanlan self-excited force model,a vortex-induced force model containing only two aerodynamic derivatives of H_(1)and H_(4)is established.By comparing with the results of vortex-induced vibration amplitude and vortex-induced vibration interval of wind tunnel test,the correctness of the vortex-induced force model and its vortex-induced aerodynamic derivative method is verified.At the same time,compared with the wind tunnel test results under different damping ratios,it is verified that the vortex-induced force model is universal.The research conclusions can provide reference for the establishment of vortex vibration mechanism and vortex excitation force model ofΠ-shaped main girder section.