行车荷载下钢管混凝土系杆拱桥冲击系数的数值模拟

Numerical study on the impact coefficient of the concrete-filled steel-tube tied arch bridge subjected to the vehicle loading

相比梁桥,对行车荷载下钢管混凝土系杆拱桥振动响应研究较少,且已有研究多取跨中作为观察点来评估桥梁的振动效应。为评估钢管混凝土系杆拱桥的车致振动特性,在有限元软件ABAQUS中建立了全桥有限元动力分析模型,采用板单元模拟桥面板,梁杆单元模拟系梁、横梁、拱肋、风撑和吊杆,并模拟施加移动车辆,获得了不同桥跨位置处的动挠度响应,并与现场动挠度实测结果进行对比,表明了分析模型的正确性。继而,研究了不同车速、轴重及行进路线工况下1/4、1/2和3/4桥跨位置处的动挠度响应,获得了不同桥跨位置的冲击系数。结果表明,系杆拱桥冲击系数随车辆轴重增加而减小,随车速增加先增大后减小,且车辆行进路线距桥面中线越远则冲击系数越小。将上述不同荷载工况的冲击系数与规范和已有经验模型进行对比,发现系杆拱桥最不利冲击位置并不位于桥梁跨中位置。研究结果可为类似系杆拱桥冲击振动安全工程提供参考。

In order to evaluate the special vibration features of the arch-shaped bridge of the concrete-filled steel tube under the vehicle loading,we have built up a 3-D finite element model of a full bridge by way of using a commercial software known as ABAQUS . At the same time,we have compared the vibrations of the tied arch bridge of the concrete-filled steel tube subjected to the vehicle loadings with the traditional beam bridges. Moreover,the current existing studies can generally be taken as the bridge mid-span as an observation point to evaluate the vibration effects of the bridge. Thus,the bridge deck can be described by the plate elements,whereas the beam and the rod elements are adopted as for modeling the tie beam,the cross beam,the rib,the wind bracing and the bridge suspender,respectively. The dynamic deflection responses at the different bridge locations can be worked out by using the established model through a moving truck load. Thus,the computational results can generally be compared properly with those gained by the field tests on the same bridge,which can validate the proper regularity of the current finite element model. Thus,following the dynamic deflection responses at 1/4,1/2 and 3/4 span locations of the bridge,it would be possible to analyze and work out the travelling truck at different speeds,the axle loads and the different routes the trucks had been moving along,with the dynamic impact coefficients being evaluated correspondingly. That is to say,the impact coefficient of the tied arch bridge tends to decrease with the increase of the axle load of the truck and with the increase of the space between the truck route and the central axis of the bridge.As for the truck speed increase,it can be found that,not until the impact coefficients increase to its maximum at 50 km/h,it would be decreasing to a smaller speed. Especially,when comparing the impact coefficients obtained for above loading cases with the results given by the code and the published empirical formula,it can be found that the most unfavorable location for the bridge loading impact ought not necessarily to be at the mid span. Thus,the research results can be made to serve as a reference to the loading impact safety control engineering for the similar weight-bearing arch bridges.