Study On Dynamic Characteristics Of Highway Bridge Under Moving Load

Vehicle load is the main form of load borne by bridge in the process of operation.When the vehicle passes on the bridge in a certain state,there is a complex interaction and reaction relationship between the vehicle and the bridge,and this repeated interaction between the two has a non-negligible impact on the service state of the bridge.Therefore,it is very important to carry out dynamic characteristics analysis of the bridge under the action of moving load.Taking Donghuan Bridge in Lipu County,Guilin City,Guangxi Zhuang Autonomous Region as the engineering background,this paper analyzes the dynamic characteristics and impact coefficient of the bridge under the action of moving loads in multiple working conditions by numerical simulation method,and provides some references for the design and operation of such Bridges.The main research contents and achievements of this paper are as follows:(1)The vehicle-bridge coupling analysis model is established,and the dynamic characteristics of highway Bridges under different vehicle speeds,different vehicle loads and different vehicle numbers are systematically analyzed from the time domain and frequency domain,and the impact coefficient of the bridge is also analyzed.(2)By analyzing the time-history response of displacement and acceleration of the midspan section of the bridge under three working conditions,the dynamic characteristics of the bridge under moving loads are analyzed from the time domain.The results show that vehicle speed,vehicle load and the number of vehicles across the bridge all affect the dynamic characteristics of the bridge.With the increase of vehicle speed,the peak displacement and acceleration of bridge mid-span section do not linearly increase,and the relationship between vehicle speed and peak displacement and acceleration is complex.With the increase of vehicle load,the peak displacement and acceleration of bridge mid-span section increase linearly.When the number of vehicles across the bridge increases,the peak displacement and acceleration of the mid-span section of the bridge also increase linearly,and the peak value of the transverse multi-vehicle is greater than that of the longitudinal multi-vehicle.(3)By comparing and analyzing the displacement and acceleration peaks of the middle section of the side span and the middle span of the bridge,it can be concluded that under three working conditions,the displacement peak of the middle section of the side span is greater than that of the middle span,while the acceleration peak is smaller than that of the middle span.Therefore,in order to ensure the safety and reliability of bridge side span,the design of bridge side span should be strengthened in the bridge design stage.(4)By analyzing the spectrum response of the bridge mid-span under moving load,the dynamic characteristics of the bridge under moving load are analyzed from the aspect of frequency domain.The results show that with the increase of vehicle speed,the mid-span section of the bridge will stimulate higher modes to participate in the bridge vibration,which will strengthen the local vibration of the bridge.With the increase of load or the number of vehicles,the high-order modes of vibration will not be excited in the mid-span section of the bridge,but the acceleration amplitude of the bridge will be changed.(5)Finite element software is used to calculate the impact coefficient of the mid-span section of the bridge under three working conditions,and the change law of the impact coefficient of the bridge under moving load is obtained.The results show that the impact coefficient of the mid-span section of the bridge changes significantly under the three working conditions,but the impact coefficient of the bridge does not change linearly with the increase of vehicle speed.The impact coefficient of bridge decreases linearly with the increase of vehicle load and vehicle number.