随机风、车流联合作用下大跨公路悬索桥纵向振动特性研究

为了研究随机风、车流荷载联合作用下大跨公路悬索桥纵向振动特性，基于元胞自动机原理建立了随机交通流模型，采用平稳高斯过程模拟风荷载，同时考虑随机风、车流与桥梁的相互作用，利用ANSYS和MATLAB混合编程技术建立了风-车-桥空间耦合振动分析平台，并基于该平台对随机风、车流荷载单独作用以及联合作用下某大跨公路悬索桥加劲梁的纵向位移时程、纵向位移极值和纵向累积位移等特性进行了深入的研究。研究结果表明：低风速下（5 m·s^-1）由单风引起的加劲梁纵向位移极值要远小于由单车（流）引起的加劲梁纵向位移极值（不足5.0%）。当风速增加至20 m·s^-1时，风致加劲梁纵向位移极值分别为稀疏交通流和轻微拥堵交通流引起加劲梁纵向位移极值的57.7%和24.2%。此外，还发现风-车-桥耦合效应显著，若不考虑风-车-桥耦合效应的影响而采取单个荷载效应线性叠加的方法，将明显低估加劲梁纵向位移的极值响应。风荷载单独作用下加劲梁纵向位移极值的概率分布均服从对数正态分布；车流荷载单独作用以及风、车流荷载联合作用下加劲梁纵向位移极值的概率分布均服从广义极值分布。虽然风荷载对加劲梁纵向位移极值的贡献与车流荷载相比要小很多，但由于风致加劲梁纵向振动的频率较高，风荷载对加劲梁纵向累积位移的贡献要比对纵向位移极值的贡献显著。

Longitudinal Vibration Characteristics of a Long-span Highway Suspension Bridge Under Stochastic Wind and Traffic Loads

In the present study, a numerical framework was proposed to investigate the longitudinal vibration characteristics of long-span highway suspension bridges under the combined actions of wind load and traffic load. In the numerical framework, a stochastic wind field was simulated as a stationary Gaussian process, and a stochastic traffic flow was simulated based on the concept of cellular automation (CA). The numerical framework systematically incorporated the dynamic interactions among wind, traffic flow, and bridge, which was solved using the finite element software ANSYS and the programming language MATLAB. With the established numerical framework, the longitudinal displacement time histories, maximum longitudinal displacement, and cumulative displacement of the stiffening girder under individual wind load, individual traffic load, and combined wind and traffic loads were thoroughly investigated. The results indicate that the maximum longitudinal displacement of the stiffening girder under low wind speed (less than 5 m·s^-1) is much lower (less than 5.0%) than that induced by the traffic load. Nevertheless, as the wind speed increases to 20 m·s^-1, the wind-induced maximum longitudinal displacement of the stiffening girder increases to approximately 57.7% and 24.2% of those induced by a free-flow traffic load and moderate-flow traffic load, respectively. In addition, it is found that the coupling effects due to wind-vehicle-bridge interaction is significant, and the use of a superposition approach by ignoring the coupling effects could lead to significant underestimation of the maximum longitudinal displacement of the stiffening girder. Moreover, the results show that the maximum longitudinal displacement of the stiffening girder under individual wind load follows a log-normal distribution, while the maximum longitudinal displacements under individual traffic load or combined wind and traffic loads follow the generalized extreme value distribution. Finally, the results indicate that, although the contribution of wind load to the maximum longitudinal displacement of the stiffening girder is insignificant compared to that induced by the traffic load, the contribution of wind to the cumulative displacement cannot be ignored. This is due to the fact that the vibration frequency of the wind-induced longitudinal displacement time histories is much higher than those induced by the traffic load.