Effect Of Uneven Vehicular Overloads On The System Reliability Of Simply Supported Girder Bridges

With the rapid development of the national economy,the traffic volume is increasing,and the number of heavy trucks is increasing.On the one hand,the bridge collapse,overturning and other accidents caused by the heavy-duty vehicles are common,which seriously endanger the safety of the existing old Bridges.On the other hand,in engineering practice,the mechanical indexes of bridge structure in the limit state of normal use are mainly considered,and the nonlinear force characteristics in the limit state of bearing capacity of beam bridge system need to be further discussed.Therefore,for the simple supported beam bridge system of multi-main beams,it is necessary to discuss the structural stress caused by the uneven distribution of heavy load.Therefore,this paper establishes a heavy load model based on the measured vehicle load data of WIM,and carries out the influence of the heavy load uneven distribution on the reliability of the simple supported beam bridge system.The main contents are as follows:(1)Establish a typical heavy-load vehicle model based on the measured WIM data,and set multiple heavy-load heterogeneous distribution conditions according to the number of lanes,eccentric distance and vehicle distance.Taking the prestressed reinforced concrete simply supported beam bridge as the research object,the nonlinear finite element model is established,considering the influence of heavy load,calculate the mechanical index of the main beam under the action of each eccentric distance,and analyze the bending moment-curvature curve of the main beam under the condition of heavy load.(2)The lateral distribution coefficient of load under the nonlinear force state of beam bridge is calculated by fractional method and compared with the value of conventional theoretical algorithm.By analyzing the change pattern of the lateral distribution coefficient of the main beam load with the heavy load eccentric distance,the probability distribution type of the transverse distribution coefficient of each main beam load is obtained by using Matlab fitting distribution toolbox.(3)The stochastic reliability theory is introduced,and the limit state equation of the main beam is constructed based on the limit state of bearing capacity.JC method is used to calculate the reliability index of each girder,and compared with the reliability of bridge design target to obtain the influence of uneven distribution on girder reliability.The changing trend of main beam reliability index and the changing pattern of main beam reliability index with nonuniform distribution are analyzed.(4)combined with the series system failure probability calculation,calculated the uneven conditions of simple beam bridge system of failure probability change,under different conditions of system failure probability change rule comparative analysis,get the simple beam bridge system under the most unfavorable state overload distribution rule,for the old beam bridge reinforcement and bridge design provide effective Suggestions in the future.