高铁连续梁桥龙卷风荷载数值模拟

为探明高铁连续梁桥龙卷风荷载特征，采用计算流体动力学手段，开展了高铁连续梁桥龙卷风荷载数值模拟研究。首先，以Ward型龙卷风发生装置为物理原型，按照原理相仿和等效替代的原则建立了相应的数值模型。然后，基于上述模型开展龙卷风场数值模拟，并与文献提供的风洞试验结果进行对比，验证了数值龙卷风场的准确性。在此基础上，以某大跨度高铁连续梁桥为工程背景，将该桥三维模型建于上述数值龙卷风场中心，研究龙卷风作用下高铁连续梁桥结构表面风压的分布规律。研究结果表明：数值模型可较好地模拟龙卷风场的基本特征；龙卷风袭击高铁连续梁桥时，风场受主梁和桥墩的干扰较大，涡核结构发生明显变化，其中，主梁底部风场的涡核半径增大，形成较大范围的高风速区；桥梁结构表面存在较大压差，正负风压极值之差约为负风压极值的2.5倍；负风压出现在主梁跨中的较小范围内，且主梁顶面的负压绝对值高于主梁侧面和底面；正风压极值出现在主梁端部迎风侧，且桥墩迎风侧也承受较高的正风压作用。上述极端不均衡的风荷载在桥梁设计时应予以重视。

Numerical Simulation of Tornado Loads on a High-speed Railway Continuous Girder Bridge

To investigate the characteristics of the tornado load on continuous girder bridges of high-speed railway, this study simulated the tornado load mentioned above by computational fluid dynamics method. Specifically, using the Ward-type tornado simulator as the physical prototype, a numerical model was built based on similar configuration and equivalent substitution principles. The numerical wind field was then validated by a reference experiment conducted in a Ward-type simulator. By taking a long-span high-speed railway continuous girder bridge as the engineering background, a three-dimensional model of the bridge was laid in the center of the numerical tornado field. The wind pressure characteristics of the bridge were investigated. The results show that the numerical model is able to simulate the essential characteristics of a tornado field. When a tornado strikes the high-speed railway continuous girder bridge, the vortex changes significantly because of the interference of the girder and piers. A large core radius is found underneath the main girder, forming an area of high wind speed. A significant discrepancy in the wind pressure is obtained on the surfaces of the bridge, with difference between the positive and negative wind pressure appears being approximately 2.5 times that of the negative peak pressure. The negative pressure appears in a small area of the middle span of the main girder. The negative pressure value on the top of the girder is lower than that on the side and the bottom. The maximum positive wind pressure appears on the windward side of the end of the girder. The windward sides of the piers also experience a high positive wind pressure. The highly unbalanced wind loads mentioned above should be considered in designing high-speed railway continuous girder bridges.