Time-varying Dynamic Characteristics Of Simply Supported Beam Bridges Under Coupling Of Temperature And Vehicle

Most bridge structures are affected by running vehicles and external environment(such as temperature)for a long time during their service period,which will cause changes in the dynamic characteristics of the bridge.Such changes will even cover up the changes in dynamic characteristics caused by bridge damage,and it is easy to cause inaccurate vibration-based bridge safety monitoring.Therefore,accurately grasping the evolution law of dynamic characteristics during bridge operation plays a positive role in safety and health inspection and state evaluation of bridges.Environmental factors,especially temperature,will cause significant changes in bridge modal parameters,which will make the damage identification method based on dynamic characteristics ineffective.Previous studies have shown that temperature and vehicle action are the two most important factors that cause structural dynamic characteristics variation.These two factors often act on the bridge structure at the same time,and will produce certain coupling effect.Therefore,studying the changes of modal parameters and internal mechanism of bridge structure under the action of temperature and vehicle,revealing the time-varying mechanism of dynamic characteristics of simply supported beam bridge under the coupling action of temperature and vehicle,can provide theoretical basis for safety monitoring of railway bridge structure.First of all,the 1 / 4 car body model-simply supported beam bridge is taken as the research object.Based on the ANSYS finite element software,the finite element model is established by displacement contact method,and the influence of temperature on the modal frequency of simply supported beam bridge is analyzed.Then,based on the assumption of short time invariability,the change of modal frequency and mode shape of the simple supported beam bridge coupling system under the joint action of temperature and vehicle is studied.The parametric analysis is carried out by using the finite element model,and the change of modal parameters of the coupling system under the action of different temperature modes,vehicle bridge mass ratio and single or multiple vehicles is discussed.The results show that the two factors often act on the bridge structure,which will change the modal frequency of the coupling system;the modal frequency and mode shape of the coupling system become regular time-varying under different temperature,vehicle bridge mass ratio and other main factors.Finally,a simple supported beam bridge model test under the action of a mobile car is designed to study the time-varying law of the dynamic characteristics of the mobile mass car and the mass spring car to the simple supported beam bridge,and further verify the correctness of the numerical simulation.