Study On Extreme Probability Of Intermediate And Small-span Bridge Action Effects Under Continuously Growing Traffic Loads

With the rapid expansion of the transportation industry,highway traffic volume and load capacity are constantly increasing,the problem of vehicle overloading is becoming more and more serious,endangering the operation safety of existing bridges.Based on the measured vehicle data of highway WIM,this paper studies the extreme value of the load effect of the simple supported beam bridges with different spans under the effect of random traffic,and compares it with the design load code;Introduce traffic volume interval growth model,predict the extreme value of the load effect of simply supported beams under traffic volume growth,and analyze the influence of traffic volume growth on the extreme value of the load effect of small and medium span bridges;Based on the measured vehicle flow data,an extrapolation method for vehicle dynamic effects of bridges considering bridge-bridge coupling vibration is proposed.The vehicle dynamic effect extreme values of a simply supported T-beam bridge are predicted,and the guarantee rate of current vehicle load design models in various countries is evaluated.The main content includes the following aspects:(1)Based on the measured data of a highway dynamic weighing system(WIM),the vehicle parameter characteristics distribution types and distribution parameters are fitted,and the vehicle load probability model is established.The generalized extreme value theory(GEV)was used to extrapolate the extreme value of the vehicle load effect of each span of simply supported beams in the design reference period,and compared with the highway-I design load specification.(2)An extreme value probabilistic analysis method of vehicle-borne effects of small and medium-span bridges considering the annual growth rate of traffic volume is proposed.A typical example verifies the effectiveness of the analytical method for extrapolating bridge extremums based on WIM data and the annual growth rate of traffic volume.The maximum bending moment of the simply-supported T-beam under the increase of trafic volume is predicted based on the measured traffic data of WIM,and the influence of the increase of traffic volume on the extreme value of the load effect of the bridge is analyzed.(3)Based on the classic vehicle-bridge coupled vibration theory,a method for extrapolating the bridge effect extreme value under the impact of vehicle load is proposed.Based on the measured traffic flow,the dynamic effect extreme value of the simply supported beam is predicted,the influence of the road surface deterioration on the bridge load effect extreme value is analyzed,and the design vehicle load model of the small and medium-span bridge is calibrated.