桥面不平顺对下承式系杆拱桥振动影响的试验和模拟研究

为了获得下承式系杆拱桥的汽车荷载冲击系数，在桥面间隔布置橡胶减速条带以形成周期性的不平顺输入，对下承式钢管混凝土系杆拱桥的动挠度进行现场实测。结合自编的车桥耦合（VBI）单元，建立车-桥耦合振动三维有限元分析模型，通过与实测结果对比验证VBI单元的正确性。在此基础上，引入另外3座标准拱桥以形成涵盖4种跨径的下承式系杆拱桥研究对象，输入规范规定的A~D级不平顺，研究车速、车重和桥梁基频对系梁冲击系数的影响。研究结果表明：汽车通过周期间隔布置的减速带时会形成稳态激振，当激振频率接近桥梁的前2阶基频时，引起的系梁动挠度响应最大；系梁的汽车荷载冲击系数随着桥梁基频的增加呈现出先增大后减小的趋势，当小汽车（总重低）行驶于差桥面（D级不平顺）时，规范值明显低估了系梁的冲击系数。

Experiment and Simulation Study on Influence of Bridge Surface Roughness on Vibration of Through Tied Arch Bridge

To determine the impact factor of a through-tied arch bridge traversed by a moving vehicle,in-situ measurements were conducted on the dynamic deflection of a through-tied concrete-filled steel-tube-arch bridge that was excited by a truck moving on a rough bridge deck formed by periodically spaced rubber bumps.The coupled vehicle-bridge vibrations were simulated by a 3Dfinite element model of the test bridge,in which the vehicle loading was introduced through a self-developed vehicle-bridge interaction(VBI)element.The correctness of the VBI element was verified by comparison with the test results.Three additional standard tiedarch bridges were then introduced to form a boarder research object through tied-arch bridges covering four different span lengths.With the input of grades A-D standard road roughness into the VBI element,the influences of the vehicle speed,vehicle load,and fundamental bridge frequency on the impact factor of the bridge collar beam were studied numerically using the established finite element models.It was shown that steady excitations to the bridge can be formed when the truck moves over the periodically arranged road bumps.The maximum dynamic deflections of the collar beam can be observed when the excitation frequency is close to the first two fundamental frequencies of the bridge.The impact factors of the bridge collar beam are found to increase initially and then decrease with the increase in bridge fundamental frequencies.For a vehicle with small axle loads(e.g.,car)moving on a tied-arch bridge with poor roughness(e.g.,grade D roughness),it is concluded that the impact factor of the collar beam is obviously underestimated by the bridge design code.