A Research On Load Model And Load Effect Of Vehicle Congestion On Municipal Bridges

With the improvement of the level of urbanization in China,traffic congestion has become a common phenomenon in municipal traffic,and the trend of congestion development is becoming more and more serious.Vehicle congestion not only causes the waste of resources and environmental pollution,but also forms a cumbersome to the social and economic development,and even does harm to people’s physical and mental health.Meanwhile,vehicle congestion will also cause concrete cracking and deflection on municipal bridges,abutments,expansion joint,bridge deck pavement damage and some other damage.Therefore,it is urgent and necessary to make a timely and feasible study on the congestion of municipal bridges and vehicles.Based on the statistical analysis of the traffic characteristics of municipal bridges and the type of the vehicles,this paper presents an economical and applicable method of collecting traffic load parameters manually,and simulative experiments conducted in a parking lot in a university have proved the feasibility and accuracy of the method.With the collection of data like types of vehicle on municipal bridges,vehicle-bridge spacing,wheelbase,axle load,the author conducted fitting analysis of data parameters according to the probability statistics method and kernel density estimation method and calculated the various parameters of a vehicle bridge city representative value to single lane congestion load model and four lane girder vehicle city bridge load spectrum and multi lane traffic load model.With the establishment of a real bridge model by finite element software,the author analyses the load effect of bridge under different congestion load model,compared the relationship between the contrast of single lane and multi lane traffic congestion load effect,and made statistics of different congestion load model frequency,and finally got four lane transverse fold calculated city bridge vehicle congestion reduction coefficient according to the engineering example.The thesis studies bridge congestion vehicle load model in 6 cities including the composition of small cars,medium-sized passenger cars,large passenger cars,considering either the single lane congestion load effect or multi lane traffic load effects are far less than the bridge design load effect,the vehicles congestion on municipal bridges normally does not pose a direct threat to the safety of the bridge structure.Through the actual single and multi Lane congestion load effect,the lateral reduction coefficient of four lanes in municipal bridges is 1.00,0.87,0.68 and 0.47 respectively.The fatigue problem caused by traffic load on municipal bridges can not be ignored either.In this paper,the fatigue failure mechanism and fatigue calculation theory of reinforced concrete bridges are analyzed,and the frequency spectrum of vehicle loads and standard fatigue models of municipal bridges are determined.Finally,the author used the fatigue cumulative damage theory based on S-N curve method to calculate the formation of different loads and different congestion,and the fatigue life under different stress levels.The results show that fatigue damage caused by frequent traffic congestion on municipal bridges,but within a few years the fatigue cumulative damage does not exceed the rated value,it will not affect the normal life of the bridge.