Research On Concrete Beam Bridge Load Effects Of Actual Vehicle Operating Status

As one of the most important variable loads in bridge structures, vehicle load is an important cause of bridge fatigue, damage and even collapsion. The study of load models and effects under practical vehicle operation state could provide essential support for the safety, reliability, maintenance and reinforcement, and vehicle management of highway, which has profound theoretical significance and practical value in engineering. The main efforts accomplished in the thesis are listed as follows:(1) After taking Xia Baishi Bridge which belongs to Shenhai-Highway G15(Funing Line) as engineering background, where the main bridge is a prestressed concrete continuous rigid frame bridge with span arrangement (145+2 × 260+145) m, the approach bridge is prestressed concrete continuous T-girder bridge with span arrangement (4×45) m, and employing Matlab software to compile programme to process the data collected by Wight-in-motion(WIM) system from May 2012 to May 2013, vehicle statistics model for Xia Baishi Bridge under practical operation state was established.(2) The finite element model of the approach bridge of Xia Baishi Bridge was built, the load effect influencing line of key cross-section was obtained through calculation, based on equilibrium renewal stochastic process and Monte Carlo Simulation, the vehicle load model of the approach bridge of Xia Baishi Bridge was investigated, therefore, the vehicle load effect models of different load evaluation reference periods were established.(3) Based on Monte Carlo Simulation and Extreme Value Theory, the vehicle abnormal operation states of Xia Baishi Bridge and its approach bridge were simulated, after which the vehicle load effect model under abnormal operation state was analyzed, and the bearing capacities of Xia Baishi Bridge and its approach bridge under abnormal operation state were checked respectively.The main conclusions are listed as follows:(1) Under practical operation state the probability distribution of the maximum value of vehicle load effect of continous beam bridge appeared to be multimodal distribution. the total weight, axle weight, distance between axles of practical operation vehicle complied with Mix Gauss Distribution, and distance between vehicles complied with lognormal distribution or Weibull Distribution.(2) Based on Equilibrium Renewal Stochastic Process Theory and Monte Carlo Simulation, the maximum value distribution of load effect of approach bridge of Xia Baishi Bridge under normal operation state was obtained respectively, the difference was within 10% and they were both applicable for the evaluation of vehicle load effect of bridge under normal operation state. Vhicle load effects of different evaluation reference periods under actual normal operation state were 1.07-1.20 times of the highway-I level standard load.(3) The maximum value of vehicle load effect in critical positions of each lane of Xia Baishi Bridge under abnormal operation state complied with Generalized Extreme Value Distribution. The vehicle load model of Xia Baishi Bridge could take 1.37 times of that of the highway-I level standard load, and 1.17 times for the approach bridge of Xia Baishi Bridge. The bearing capacity of Xia Baishi Bridge under abnormal operation state satisfied the corresponding requirements of codes, showed that it remained in safe state, while the bearing capacity of approach bridge of Xia Baishi Bridge could not meet the corresponding requirements of codes, indicated that it was in dangerous state.