Study On Overturning The Risk Ofcurved Girder Bridge Under Randomtraffic Flow

Overturning accidents of curved girder Bridges occur frequently in China,causing huge economic losses and drawing great attention from the society and the government.The structural characteristics and vehicle loads of curved girder Bridges are the main causes of accidents.From these two aspects,this paper will improve the overturning risk assessment method of curved girder Bridges to ensure the safe operation of Bridges.The original data of traffic flow were collected by using the dynamic weighing system(WIM)and video monitoring technology,and the characteristic values of traffic flow statistical distribution were used as the basis of Monte Carlo method(Monte-Carlo)to simulate random traffic flow.Then the finite element software Midas Civil was used to build the bridge grillage model,and the influence line of the reaction force of the support under the most unfavorable loading lane was obtained.Based on the calculation method of anti-overturning stability coefficient in Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTG 3362-2018),it is easier to calculate the anti-overturning stability coefficient of Bridges under continuous loading of random traffic flow.According to the influence line loading principle,the random traffic flow was loaded on the curved girder bridge,and the distribution histogram of the anti-overturning stability coefficient of the curved girder bridge was drawn.The overturning risk of the curved girder bridge was evaluated according to the overturning evaluation method presented,at the same time,the weight limit of anti-overturning vehicles is studied for Bridges with moderate or above overturning risk.The main content includes the following five aspects:(1)The research status of anti-overturning stability and random traffic flow load model of curved girder bridge is described,and the detailed process of overturning risk assessment method of curved girder bridge with random traffic flow is given.Several probability distribution types commonly used in traffic load analysis and hypothesis testing of statistics are introduced.(2)The traffic flow data collected from a bridge head in the main urban area of a city based on the dynamic weighing system(WIM)and video monitoring technology were analyzed for the characteristics of traffic flow parameters.According to the principle of Monte Carlo method,Matlab was used to sample the parameters such as vehicle models,workshop distance and vehicle weight in the day and night respectively,and a random traffic flow of 50,000 vehicles was generated.The influence line of bearing reaction at the most unfavorable loading position was extracted from Midas Civil,and then the reaction force of each bearing was calculated under the principle of influence line loading,and the anti-overturning stability coefficient under continuous traffic load was solved according to the modified calculation method of anti-overturning stability.(3)A qualitative method for overturning risk assessment of curved girder Bridges under random traffic flow is proposed.The distribution histogram of anti-overturning stability coefficient was obtained under the loading of random traffic flow,and the probability value of the 2.5 determination coefficient was obtained by using the method of function fitting,so as to judge the overturning risk index of the bridge.(4)For Bridges with moderate overturning risk or above,study on anti-overturning vehicle weight limit,and work out the corresponding vehicle weight limit tonnage.(5)The overturning risk assessment of curved girder Bridges under random traffic flow in the main urban area of a city is carried out.