Model Test And Finite Element Analysis Of Cable Breakage Response For An Irregular Arch Bridge With Inclined Arch And Curved Beam

Cables are the key components of transmission arch bridges,which may undergo environmental erosion and excitation of moving load,resulting in cables prone to cracking,safety reserves of the cable reduced,stress amplitude gradually increased,when the maximum stress closed to the ultimate bearing capacity will eventually lead to the sudden breakage of cables in the operation stage,and then the deck occurred irregular concave or even collapse,the safety of the arch bridge operation caused great threat.Therefore,it is necessary to analyze the degradaion process and mechanism of transmission of mechanical properties of remaining structure under the effects of cable-loss scenarios.The current scholars mostly perform numerical simulations of broken cables in the form of linear simplified girder bridges with equal height and width sections.Compared with the conventianal bredge,while the force transmission mechanism of the special-shaped arch bridge composed of an inclined arch and a curved beam are more complex,and which bending-torsion coupling effect is more obvious,and there are few studies on the impact effect of cable breaking and the regularity of internal force redistribution on such bridges.Thus,baesd on the similarity ratio theory,a new type steel bridge composed of an inclined arch and a curved beam was ued as a prototype and the scaled model with a geometric similarity ratio of 1:40 was fabricated to carry out a cable beaking simulation.Ansys is used as finite element analysis software for spatial mode of the original bridge and scaled model,and the research on the subject is performed through cable freacture results from the finite element simulation and the test results wrer verified and compared with each other.The major research works are as follows:(1)Taking Haixin Bridge as an example,Finite element spatial modelling of the complete bridge and parametric analysis of simulated broken cables,achieved through the parametric design language Ansys Apdl.The cable breaking at different positions,different numbers of broken cables and different failure interval of adjacent cables are calculated.The main girder and arch rib’s deflection,main girder and arch rib’s stresses and the the remaining cables’ internal force were selected as research indexes to evaluate the degree of impact effect of broken cables on this type of arch bridge.The main conclusions show that: duration time of cable breaking,which accurately reflects the impact response of cable breaking,was determined though comparative analysis of finite elements.The trend in the mechanical propertied and the regularity in the internal force redistribution of the remaining structure of the arch bridge composed of an inclined arch and acurved beam after the sudden breakage of cables were identified.Discussion and analysis of the DAF for the remaining members after the cable breaks at typical locations.The dynamic response of multiple cables breaking at the same time cannot be simplified as a linear superposition of single cable breaks one by one.(2)Based on the validated methods of finite element modeling and cable breaking simulation.Taking Haixin bridge as an example,based on the similarity ratio theory,the scaled moedl with a geometric similarity ratio of 1:40 was design and fabricated.A detailed description of the equivalence design and calculation process of the cross-sectional geometry for main girder and arch rib,the construction design of scaled model and compensation mass distribution of main girder and arch rib were introduced in detail.Two kinds of simulations were performed to anlysys the broken cables by slowly unloading the force and suddenly breaking the cable.Finite element spatial modelling of the scaled model achieved through the parametric design language Ansys Apdl.The fracture results from the finite element simulation and the test results were verified and compared with each other to confirm the feasibility and accuracy of the finite element modeling method to investigate the variation rules of the static and dynamic response of the remaining members after cable breakage.It also verified the design of the scaled model and the reasonableness of the broken cable simulation test,which can truly reflect the variation rules of mechanical properties of the remaining structure after the cable breakage at the different typical location of the prototype bridge.(3)Taking a through steel box tied-arch bridge as the engineering background,based on the design stiffness ratio of the prototype arch bridge,the static response of the arch bridge under different arch-girder stiffness ratios was firstly calculated and discussed,and then the dynamic time history analysis of the arch bridge was carried out to investigate the influence of the arch bridge under different stiffness ratios by the impact effect of broken cables.The analysis shows that with the increasing arch-girder stiffness ratio,the impact effect of the adjacent cable break can be alleviated,and the distribution ratio of the cable force of the adjacent cable in the region of broken cable can also be reduced.After the sudden breakage of the cable,the downward deflection at the span of the main girder increases as the arch-girder stiffness ratio increases,and the upward deflection at the span of the arch rib decreases as the arch-girder stiffness ratio increases.