拱桥短吊杆在跳车激励下的动力特性分析

Analysis of Dynamic Characteristics of Short Suspenders of Arch Bridge under Vehicle Bump Condition

由于拱上立柱与吊杆横梁的刚度差异,大跨中承式钢管混凝土拱桥通常在拱肋横梁处产生"跳车"现象,车辆在此产生的跳车冲击效应不仅增加了短吊杆的活载内力,而且激发了短吊杆附近桥面、拱肋的剧烈振动。以一座既有中承式钢管混凝土拱桥为背景,使用ANSYS建立桥梁有限元模型,采用矩形脉冲荷载对跳车的冲击荷载进行模拟。计算分析表明:在跳车激励下,拱肋和桥面系将会发生剧烈振动,拱肋和桥面系不同步的振动将会使短吊杆的大部分恒载内力卸载,易引发锚具脱锚;而且,结构振动的最大幅值是在车辆经过后,并且在自由振动时期,短吊杆还会出现几次较大的应力峰值。

Because of the stiffness difference between the arch column and the suspender crossgirder,the"bump"phenomenon usually happens at the arch rib crossgirder of long-span half-through concrete-filled steel tube arch bridge.The bump impact effect caused by vehicles here not only increases the live load internal force of short suspender,but also induces the violent vibration of bridge deck and arch rib near the suspenders.Taking an existing half-through concrete-filled steel tube arch bridge as the background,the ANSYS is used to establish the finite element model for the bridge.The rectangular pulse load is used to simulate the impact load of vehicle bump.The results of the calculation and study show that the arch rib and deck systems will vibrate violently.The non-synchronous vibration of arch rib and deck systems will make most of deed load internal forces of short suspenders unloaded,which will be easy to cause the anchorage device to drop anchor.The maximum value of structural vibration is after a vehicle passes,and in the free vibration period,the short suspender also has several large stress peaks.