公铁平层桥梁桥塔遮风效应风洞试验研究

车辆经过桥塔区域时，由于桥塔的遮风效应，其气动荷载会产生突变，且公铁平层桥梁的桥塔由于纵向尺度较大，车辆经过桥塔区域时气动荷载的变化更加剧烈.为明确某公铁平层桥梁上车辆在桥塔区域的气动特性，制作了1/20大比例尺的风洞试验模型；基于优化后的测试系统，测试了车辆通过公铁平层宽幅桥梁桥塔时的气动荷载，研究了车道位置、车辆类型以及桥塔外形对通过桥塔车辆的气动特性的影响.结果表明：越靠近桥塔车道上的车辆，经过桥塔时的横向力系数、摇头力矩系数的突变量更大，正向升力也越大，因而更容易发生侧滑与侧偏；车长对车辆通过桥塔区域的性能有显著影响，长度较小的车辆具有更大的横向力系数突变量，长度较长的车辆具有更大的倾覆力矩系数、摇头力矩系数及点头力矩系数突变量；与矩形截面桥塔相比，带倒角的桥塔使得厢式货车的横向力突变量减小了43.7%，使集装箱车的横向力系数突变量减小了25.8%，且使集装箱车的摇头力矩系数突变量减小了29.2%.

Experimental Study on Shelter Effect of Bridge Tower on Single-Level Rail-Cum-Road Bridge

The shelter effect of the bridge tower brings a sudden change of aerodynamic load on road vehicles passing by. For a single-level rail-cum-road bridge with larger scale of bridge tower in the longitudinal direction, the variation of the aerodynamic load is more intense. To explore the aerodynamic characteristics of vehicles near the pylon area on a single-level rail-cum-road bridge, a 1/20 scale wind tunnel test model is built. Based on the optimized test system, the aerodynamic loads of road vehicles passing by the bridge tower are measured. The influence of lane location, the vehicle type, and the bridge tower type on the aerodynamic load is discussed. The results reveal that traveling on a closer lane to the tower increases the variation amplitude in side force coefficient and yawing moment coefficient, and the upward lift force is also larger; thus vehicles are prone to sideslip and lateral-deviation. The vehicle length has a significant impact on the aerodynamic characteristics of the vehicles passing by the bridge tower area. Vehicles with smaller length possess larger variations of side force coefficient, while vehicles with larger length possesses larger variations of rolling moment coefficient, yawing moment coefficient and pitching moment coefficient. Compared with the bridge tower with a rectangular section, the bridge tower with chamfer decreases the sudden variation of side force coefficient of a van by 43.7%, and decreases the sudden variation of side force coefficient and yawing moment coefficient of a track-trailer by 25.8% and 29.2%, respectively.