重载铁路连续刚构桥梁竖向共振监测分析

Monitoring and Analysis of Vertical Resonance of a Heavy Haul Railway Continuous Rigid-Frame Bridge

黄河特大桥为神华大准铁路(重载铁路)增二线上跨度为(96+132+96)m的三跨预应力混凝土连续刚构桥,由于线路运能提升的需要,拟将C80B和KM70列车通行速度由60km/h提升至约80km/h。为对提速后的黄河特大桥进行适应性评估,分别采用光纤光栅应力传感器、挠度传感器及振动传感器对列车编组提速过程中的桥梁应力、挠度及振动响应进行监测分析,并分析了桥梁发生竖向共振时的列车临界速度。结果表明,当KM70列车以74km/h的速度通过桥梁时,列车激励频率与车-桥耦合体系的竖向有载频率接近,桥梁挠度变化幅度及应力幅较大,且动力系数超过规范值,由此判断桥梁发生了竖向共振。建议KM70列车不提速或提速前对桥梁进行减振处理,并采用车-桥耦合方法对桥梁竖向共振进行深入分析。

The Huanghe River Bridge herewith is a 3-span prestressed concrete continuous rig- id-frame bridge with span arrangement （96＋132＋96） m and is located on the Newly-Built Second Line of Datong-Zhungeer Railway （a heavy haul railway）, Shenhua Group. Owing to the need of increasing the transportation capacity of the line, the speeds of the trains C80B and KM70 traveling on the line were to be raised from 60 km/h to about 80 km/h. To evaluate the adaptability of the Huanghe River Bridge after the speeds of the trains were raised, the fiber grating stress sensors and deflection and vibration sensors were respectively used to monitor the stress, deflection and vi- bration responses of the bridge in the process of the train marshalling and train speed raising. The stress, deflection and vibration responses of the bridge as well as the train critical speeds when the vertical resonance occurred in the bridge were analyzed. The results of the analysis reveal that when the train KM70 passes through the bridge at the speed of 74 km/h, the train excitation fre- quencies are close to the vertical load frequencies of the train-bridge coupling system, the deflection changing amplitude and stress amplitude of the bridge are great and the dynamic coefficients exceed the values as specified in the codes, from which the occurrence of the vertical resonance in the bridge can be judged. It is hence proposed that the vibration mitigation for the bridge should be handled in the situation that the speed of the train KM70 is not raised or before the speed of the train is raised and the deep-going analysis of the vertical resonance of the bridge should be imple- mented, using the train-bridge coupling method.