某大跨径双塔单索面矮塔斜拉桥动载试验研究

Tests and Research on Dynamic Load of a Long-span Extradosed Bridge with Double Low-pylons and Single Cable Plane

以某大跨径双塔单索面矮塔斜拉桥为依托工程开展数值仿真分析、动载试验和相关比较分析。分析结果表明:实测主梁前四阶竖向弯曲自振频率均比理论计算值大,结构有一定的刚度储备;实测主梁前四阶振型与计算振型基本吻合,未见明显变异区段;该桥梁的动力特性符合设计要求。在无障碍行车工况下,该桥测试部位的冲击系数均大于计算冲击系数,基本随车速的提高而提高;在制动试验和有障碍行车工况下,该桥测试部位的冲击系数相对较大,表明当桥面不平整时,桥面行车对桥梁结构的冲击效应将明显增大。对于结构基频较小的大跨径矮塔斜拉桥,按《公路桥涵设计通用规范》(JTG D60-2015)对桥梁冲击系数取值偏不安全或安全储备偏小,有待进一步研究和探讨。

Based on a long-span extradosed bridge with double-pylons and single cable plane,the numerical simulation analysis,dynamic load test,and comparative analysis are carried out.The analysis results show that the test value of natural frequency for first fourth-order about vertical bending of the main beam is larger than the calculated value,and the structure has reservation of the stiffness;the measured fourth mode shape of the main beam is basically consistent with the calculated,no obvious difference is observed.The dynamic characteristics of the bridge meet the design requirements.Under accessible traffic conditions,the impact coefficient of the bridge in the test location is greater than the calculated,which basically increases with the increasing of vehicle speed;under the braking test and obstacle driving condition,the impact coefficient of the bridge test site is relatively large,which indicates that when the bridge deck is uneven,the impact effect of the bridge structure will increase significantly with the traffic.For long-span extradosed bridges with low fundamental frequency,the value of the bridge impact coefficient calculated by General Specifications for Design of Highway Bridges and Culverts(JTG D60-2015)is unsafe or the security capacity is insufficient,which needs further study and discussion.