Fatigue Life Prediction Of Small And Medium Span PC Beam Bridge With Random Loading Under Complex Loading Condition

Vehicle load is an important cause of fatigue cracking of bridges.At present,the overload situation of freight cars occurs,and the fatigue and cracking of bridges become more and more serious,which makes us more and more worried whether the fatigue life of bridges can withstand the test of overload.In this paper,the Palmgren-Miner linear cumulative damage theory is used to calculate the fatigue damage of the bridge,and the analysis method of stochastic vehicle bridge coupling vibration is presented to simulate the dynamic response characteristics of the highway bridge under the action of actual traffic flow.The following work is done mainly:In this paper,the response characteristic of vehicle bridge coupling vibration under the action of various models is studied.In this paper,the dynamic response curve of the 1/2 model is analyzed,and the differential equation of vibration under various vehicle models is obtained and solved by the method of Newmark-beta analysis.On the MATLAB flat,a general vehicle bridge coupling vibration is developed.Dynamic analysis program.The internal force calculation method of space bridge structure is studied.First,in the car bridge coupling vibration analysis program,the corresponding response curve of the coupling vibration of the vehicle bridge is obtained.The dynamic effect of the bridge structure is analyzed with the finite element analysis method,and the characteristics of the main tensile stress time history of the corresponding bridge position are studied.Finally,the accuracy of the program is verified by two examples of simple supported beam bridge and continuous rigid frame bridge.In the study of traffic flow in the PC beam bridge with small and medium span,the vehicle load is divided into 5 types according to the corresponding traffic data,combined with the vehicle load code,considering the vehicle weight and the vehicle parameters.According to the probability density,the random traffic flow is formed,and the vehicle bridge coupling vibration analysis program is introduced to analyze and calculate the dynamic response of the small and medium span PC beam bridge under the action of random flow.The MATLAB random function is used to deal with the uneven degree of bridge deck.On the basis of the stationary random excitation of the bridge,the time domain model method is used to simulate the uneven degree of the bridge deck.The vibration response analysis of the bridge surface is added to the bridge coupling vibration analysis program,and the dynamic effect of the bridge surface at different levels is discussed.The time history curve and its variation law.Based on the vehicle bridge coupling vibration analysis method,the fatigue life evaluation problem of the small and medium span PC beam bridge is studied.After the corresponding displacement time history curve is obtained,the main tensile stress time history curve of the bridge is calculated by the space bar structure calculation program,and the bridge is combined with the rain flow meter method and the fatigue life evaluation method.The fatigue life assessment of the beam is carried out.Further discussed the parameter influence rule of fatigue life of bridge,including traffic volume growth,vehicle weight increase and bridge surface roughness.