大跨连续刚构桥下击暴流作用效应试验研究

为研究大跨连续刚构桥在下击暴流水平风速作用下的风振响应，开发了一套在大气边界层风洞中模拟下击暴流水平风速的试验装置。下击暴流水平风速剖面通过调节置于风洞中的斜板竖向位置与倾角来模拟，下击暴流时间特性通过控制两侧水平开合板运动的速度、角度来模拟。以广东虎门大桥辅航道桥为工程背景，设计并制作几何缩尺比为1：200连续刚构桥最大双悬臂状态气弹模型，进行了下击暴流瞬态风场、下击暴流稳态风场和大气边界层B类风场下连续刚构桥最大双悬臂状态气弹模型风洞试验，对不同风场下桥梁结构风致振动位移响应进行了对比分析。结果表明：采用下击暴流模拟装置在大气边界层风洞中所模拟的下击暴流水平风剖面与下击暴流经验风剖面吻合较好；采用下击暴流模拟装置实现了下击暴流风速时间特性的模拟，所模拟的下击暴流瞬态风场湍流度与目标值总体接近。在下击暴流瞬态风场下桥梁梁端横桥向位移响应时变均方根最大值约为在B类风场下梁端横桥向位移响应均方根值的2.7~6.8倍；在下击暴流稳态风场下桥梁梁端横桥向位移响应时变均方根最大值约为在B类风场下梁端横桥向位移响应均方根值的70%~230%。在下击暴流瞬态风场下桥梁梁端竖向位移响应时变均方根最大值约为在B类风场下梁端竖向位移响应均方根值的2.3~5.3倍；在下击暴流稳态风场下桥梁梁端竖向位移响应时变均方根最大值约为在B类风场下梁端竖向位移响应均方根值的90%~260%。

Effects of Downburst on Long-span Continuous Rigid Frame Bridges

To study the wind-induced response of a long-span continuous rigid frame bridge under downburst horizontal wind, a set of experimental devices for simulating high-speed downburst horizontal wind in an atmospheric boundary layer wind tunnel was developed. The horizontal wind velocity profiles of downburst were simulated by adjusting the vertical position and inclination of the sloping plate placed in the wind tunnel. The time characteristics of downburst were simulated by controlling the rotating velocities and angles of the horizontal opening and closing plates on both sides. Considering the auxiliary-channel Humen Bridge in Guangdong as an example of a long-span rigid continuous rigid frame bridge, a 1:200 geometric scale aero-elastic model of the bridge with maximum double cantilevers was developed. Three wind tunnel experiments on the continuous rigid frame bridge model with maximum double cantilevers were conducted under a downburst transient wind field, downburst steady wind field, and B-type atmospheric boundary layer (ABL) wind field, respectively. The displacements of the bridge model under different wind fields were analyzed and compared. The results show that the horizontal wind velocity profile of the downburst simulated in the ABL wind tunnel by the downburst simulation device agrees well with the empirical wind profiles of downburst. The downburst simulation device can be used to simulate the time characteristics of downburst wind speed. The turbulence intensities of the simulated downburst transient wind field generally approximate the target values. The maximum time-varying root mean square (RMS) values of the transverse displacement of the bridge deck tip under a transient wind field of downburst and under a steady wind field of downburst are 2.7-6.8 and 0.7-2.3 times that of the bridge deck tip under the B-type ABL wind field, respectively. In addition, the maximum time-varying RMS values of the vertical displacement of the bridge deck tip under a transient wind field of downburst and under a steady wind field of downburst are approximately 2.3-5.3 and 0.9-2.6 times that of the bridge deck tip under the B-type ABL wind field, respectively.