Analysis Of The Dynamic Response Of Stiffened Girders Of Large Span Suspension Bridges Under Vehicle Loads And Their Non-stationary Dynamic Reliability

With the continuous improvement of China’s infrastructure,the speed and weight of vehicles running on highway bridges are increasing,resulting in the interaction effect between vehicles and bridges cannot be ignored,especially for flexible structures such as suspension bridges,whose vehicle-bridge coupling-related problems deserve more attention.At present,there is a lack of adequate research on the dynamic response of large span suspension bridges under the action of multiple vehicles,especially on the nonstationary dynamic reliability of the vehicle response of large span suspension bridges,so this paper carries out corresponding research on the above two aspects.Firstly,the effects of vehicle weight,vehicle speed,deck unevenness,number of vehicles and vehicle spacing on the dynamic response of stiffened beams are discussed based on ANSYS finite element software;secondly,the effects of different random traffic densities and vehicle overload on the dynamic response of stiffened beams are discussed;then,the dynamic response of stiffened beams under the action of random traffic is analysed non-stationary using recurrence diagrams;finally,the dynamic response of stiffened beams under the action of random traffic is analysed based on the first overload probability and approximate transformation method.Finally,the non-stationary dynamic reliability of the stiffened beam under the action of random traffic flow is analysed based on the firstexceeded probability and the approximate transformation method.Based on the above research,the main conclusions of this paper are as follows:(1)Based on the fleet model,the dynamic response of the stiffened beam exhibits the largest vertical displacement response at L/4.The displacement dynamic amplification coefficient of each key position of the stiffened beam is positively correlated with vehicle weight,bridge deck unevenness and vehicle number;negatively correlated with vehicle spacing;positively correlated with vehicle speed in general,but there is a phenomenon that the impact effect is large at a specific vehicle speed.Based on the random traffic model,the displacement response at L/8,L/4 and 3L/8 of the stiffened beam has similar fluctuation trend,but the displacement response at L/4 is large,and the degree of large increase with the increase of traffic density.When random traffic is mixed with overloaded vehicles,the fluctuation trend of displacement response at each key part of the stiffened beam hardly changes with the increase of overload,but the average value and peak value of displacement response will increase with the increase of overload.(2)Based on the recursive graph theory,the non-stationary of the vibration signal of the stiffened beam under the action of random traffic flow was analysed and it was found that there was a relationship between the non-stationary of the vibration signal of the stiffened beam caused by different traffic densities: sparse traffic flow > general traffic flow > dense traffic flow.The non-stationary of the vibration signal at different locations of the stiffened beam also has a magnitude relationship: L/4 > L/2,and the difference of the non-stationary is larger as the traffic density increases.(3)Analysis of the dynamic reliability of the non-stationary displacement of the stiffener beam under the action of random traffic flow shows that the failure probability of each critical part of the stiffener beam is almost negligible under the action of sparse and general traffic flow;under the action of dense traffic flow,the failure probability of each critical part of the stiffener beam exists,and the dynamic reliability index at L/4 of the stiffener beam is the smallest,which is about 6.62.When the overload of overloaded vehicles in general traffic flow is not large,i.e.when the overload degree is 50% and100%,the failure probability of each critical part of the stiffener beam is almost negligible;when the overload degree is large,i.e.when the overload degree is 150% and 100%,the failure probability of each critical part of the stiffener beam is almost negligible.The failure probability of each critical part of the stiffener beam is almost negligible when the overload of the overloaded vehicles is not significant,i.e.50% and 100%;when the overload of the overloaded vehicles is significant,i.e.150% and 200%,the failure probability of the stiffener beam exists.