The Dynamic Characteristics And Reliability Of Bridge Based On Random Traffic Flows

Research in the area of bridge design is still concentrated on the study of the strength of materials and relatively few studies have been performed on traffic loads and their effects.Traffic loads have usually been assumed to be given in codes.This is mainly because it is very difficult to model traffic loads in an accurate manner because of their randomness.A complete evaluation of the condition of a bridge requires the knowledge of actual traffic load and how they are distributed to different bridge components.Basing on the traffic investigation,the master data of traffic flow is collected.In this paper,the data of the traffic investigation is processed by probability statistical method to find its distributed rule and statistical nature.Making use of Monte-Carlo method and MATLAB program and its toolbox,The RTF(Random Traffic Flow stimulate) program is improved which considered the influence of traffic flow magnitude,traffic lane assignment,type,heaver,and velocity of vehicles to the simulation of random traffic flow.Random traffic flow is simulated by The RTF program under the specified conditions.The BDANS(Bridge Dynamic ANalysis System) which programmed by our assignment group and the principle of VB is used to get the amount of deflection time-variable curve and the bending moment time-variable curve of Baishabao bridge.Through the amount of deflection time-variable curve and the bending moment time-variable curve of Baishabao bridge,the impact factor is calculated.And its regularity is studied.Random traffic flow is simulated by RTF for 720 days.The vehicles's weights are as concentrated forces. Through the method of influence-line loading,the bending moment value of Baishabao bridge in the mid-span section is calculated per second.The value of the maximum bending moment is recorded per day.According to the date of the 720 days' maximum bending moment value,the failure probability and reliability index of Baishabao bridge is calculated,which offers basis for safety assess.And the changes of the failure probability and reliability index is analyzed under different traffic conditions.