Research On Suspender Fatigue Performance And Structural System Safety Of Long-span Tied Arch Bridges Based On Random Traffic-bridge Coupled Dynamics

Highway bridges are subject to highly random traffic loads in the sense of time and space.The development of numerical analysis methods for coupling dynamics of random traffic flow and bridges can improve the accuracy of the assessment of bridge vibration response,which is of great significance.At present,the chain damage accidents caused by the broken suspension rods of long-span tied arch bridges are emerge in an endless stream.The research on the fatigue effect of the arch bridge suspenders caused by the vehicle load and the robustness of the arch bridge system after the cable break is becoming more and more important.Taking the Chuangye Bridge(long-span tied arch bridge)as the research background,this paper proposes a numerical research method of random traffic flow and bridge coupled vibration based on cellular automata micro-simulation,based of which,this paper carry out the research on fatigue reliability of longspan tie arch bridge hanger rod and system robustness of hanger rod failure,to form a calculation method of boom failure under the operating environment of broken cable-car-bridge coupled vibration.The dominating research contents and achievements include:(1)The numerical analysis method and program development of stochastic vehicle-bridge stochastic vibration is carried out.According to the classical vehicle-bridge couple theory,the couple vibration equations are derived and implemented based on the integral solution method of model superposition and the discrete iteration method of the step iteration respectively.Based on the MSCA,a micro-simulation program of stochastic traffic flow exploited by the research group and combining the vehicle-bridge couple theory,a numerical analysis ideology of the stochastic traffic-bridge couple vibration is developed as well as the program realization and verification are carried out.In the same time,the coupling vibration characteristics of Chuang Ye Big Bridge with the effect of random traffic flow are studied.The results show that: the numerical analytical method proposed in the paper has great accuracy and efficiency for coupling vibration investigation of the arbitrary bridge structures under any given traffic conditions.The analysis of Chuang Ye Big Bridge indicates that the road roughness,vehicle speed,vehicle weight and vehicle flow have effects on the dynamic response of bridge,in which the effect of the roughness and vehicle weight is significant.(2)The fatigue reliability methods of the arch bridge under the effects of the traffic flowbridge couple vibration is established,which involve the dynamic-stress-history analysis of the hangers,rainflow fatigue cycle calculation method,Miner linear cumulative damage assessment,corrosion degradation model of hanger resistance and fatigue reliability analysis method of hangers,etc.Firstly,the fatigue life and reliability of hanger without considering corrosion are analyzed and compare with the calculation of the specification to emphasize the vulnerable hanger position.Furthermore,the fatigue reliability of the hanger with the service life under the hanger corrosion and vehicle vibration excitation is taken into account.The results show that the fatigue life of the hanger group not consider corrosion is exceeds 20 years,the fatigue failure time of short hangers is sooner than other hangers.Considering the corrosion of the hangers,the fatigue life of short hanger remains 7 years when has been in operation for 10 years,and requirements of the service life for several other hangers is inferior to 20 years,which should be attached importance in the bridge operation.(3)In the paper,the robustness of the structural system of the tied-arch bridge caused by hanger abrupt breakage.Firstly,the arch bridge hanger robustness analysis approach the simulation method of the hanger abrupt fracture are estabilished by combining with the research statusof bridge robustness.Subsequently,the sensitively analysis of hanger breakage is carried out through the static and dynamic methods.Finally,a conple vibration analysis approach of breakcable-vehicle-bridge is eastblished to calculate the hanger failure of arch bridge under vehicle load.The results has showed that: the hanger failure causes the stress redistribution of adjacent hanger,and the failure distribution the hanger at the arch foot is the most obvious.The dynamic effect of the hanger failure cannot no be ignored on account of the stress of adjacent hanger break though the admit stress at the time of failure.The stress variation of adjacent hanger presents the coupling effect effectively in the couple vibration analysis of breakcablevehicle-bridge,which indicates the dynamic microscopic influence of hanger breakage of vehicle-bridge couple vibration in the vehicle running state.A set of numerical analysis approach of stochastic traffic flow and bridge vibration is established,which applied to the fatigue reliability assessment of hangers and the robustness research of the arch bridge structure under the hanger breakage in Chuang Ye Big Bridge,so as to provide the strategy for the operation and maintenance of bridge.The relevant research approaches can be applied to the response analysis of arbitrary bridges,though the calculation in the paper are based on the practical engineering,which further furnish a methodological basis for the count of system robustness under the fatigue and failure of the diverse bridge components.