Study On The Robustness Of Bridge Deck System Of Half-through And Through RC Box Arch Bridge

Reinforced concrete box arch bridge is widely used with the unique advantages.This bridge type originated from the process of light exploration of arch bridge ring.In recent years,however,there have been a number of accidents in the collapse of arch bridges,which were mostly concentrated in the half-through or through arch bridges,and the characteristics of these collapse accidents were progressive collapse of bridge deck system caused by the suspender fracture,which belongs to the research category of structural robustness.At present,the researchs on mechanism of progressive collapse of the half-through and through arch bridge deck system are not perfect enough,and the evaluation index of structural robustness of bridge deck system should to be improved.This paper takes a half-through reinforced concrete box arch bridge as the background and based on the summary of the collapse accidents of the half-through and through arch bridges,and then studies the progressive collapse mechanism of suspended bridge deck system under the circumstances of suspender fracture through theoretical calculation and numerical simulation,and then studies the evaluation index method of structural robustness of suspended bridge deck system.The main content of the study and the results are as follows:(1)This paper summarized the half-through and through arch bridges collapse accidents in the last 20 years in China,and analyzed the suspened bridge deck systems forms of these collapse bridges.And the conclusion showed that suspender fracture was the external cause of bridge deck system progressive collapse,and the bridge deck system took transverse beam forced mainly is the internal cause of the collapse.and then emphasised on generalizing the development and present situation of the mechanism research and evaluation index on structural robustness,as well as the codes for design of anti progressive collapse.(2).This paper has analyzed the force and deformation of transverse beam and bridge deck on bridge deck system with the form of transverse beam forced mainly,and concluded the influence factors of the mechanical properties.From the aspect of dynamic analysis,this paper has analyzed the dynamic impact amplification factor ? of suspender fracture on simplified bridge deck system by simulating abrupt hanger to equivalen reverset impact load through ABAQUS software,and the conclusion showed that the dynamic impact amplification factor ? was ranged from 1.5~1.8,which could satisfy the common assumptions ranged from 1.5~2.0.(3)This paper has analyzed structure collapse index of suspended bridge deck system by taking the relative displacement between suspender transverse beam as the collapse index of bridge deck and taking maximum allowable tensile stress as suspender fracture index through ABAQUS software establishing refinement model.This paper proposed a progressive collapse ana analysis method for suspened bridge deck system based on alternate load path method,and provided the progressive collapse analysis procedure of bridge deck system of half-through and through reinforced concrete box arch bridges.(4)This paper has simulated the bridge deck system collapse process for a box arch bridge,and analyzed the effects of different suspender fracture combination on bridge deck system with the index of structure displacement and stress through ABAQUS software.The conclusion showed that single suspender fracture will not cause progressive collapse of bridge deck system;two adjacent suspender fracture will cause progressive collapse of bridge deck system;as for two suspender in the transverse beam,only the long two suspender fracture in the middle transverse beam will cause progressive collapse of bridge deck system.(5)This paper proposed a method for evaluating robustness of suspended bridge deck system based on the fracture of suspender.By calculating the redundancy of the residual components of bridge deck system after the suspender fracture,and taking the minimum value of redundancy as the robustness index of the bridge deck system.And then this paper conducted an robustness evaluation for a arch bridge case,and compared the result with the study of bridge deck system progressive collapse in the fourth chapter,the results showed that this evaluation method of robustness based on structural redundancy is in good agreement with the simulation.