Research On Mode Of Ultimate Failure And Web Buckling Behavior Of Variable Cross-section Composite Box Girder Bridge With Corrugated Steel Webs

Composite girder with corrugated steel webs are new steel-concrete composite structures.They have advantages of light weight,long span,low cost,short construction period and so on,which are in accordance of the development of modern bridges.Therefore,composite girder with corrugated steel webs are widely used in engineering construction.The model tests of composite girder with corrugated steel webs focus on simple supported composite girder with corrugated steel webs with uniform section.There is a little research focus on continuous composite girder with corrugated steel webs with nonuniform section.Therefore,based on two test models of continuous composite girder with corrugated steel webs and finite element analysis,the failure mode and the web buckling are studied.The main work and conclusions are listed as follows:(1)Two continuous composite girder with corrugated steel webs test models I and II were casted.The span of the bridge is 2.5m+4.1m+2.5m.The difference between the two models is the reinforcement ratio,with I of 1.2%and II of 2.0%.After curing,load in the trisection point of middle span symmetrically until failure.During loading,the strain of top and bottom concrete plate,strain of steel web,deflection of the structure,shear deformation and the stress of external prestressed tendon were monitored.(2)Based on these experimental data,the strain-stress relationship in elastic and failure stages,the incensement of prestress and deflection curves,the development of cracks and the failure model of the test models were analyzed.What’s more,the failure modes of the two different test models were compared.The conclusions are as follows.In elastic stage,the shear stress of the composite structure is uniform along the height of the beam.The failure mode of the continuous composite girder with corrugated steel webs was that the bottom concrete plate cracked first.Then the top concrete plate of the middle support cracked.After that,the rebar in the middle span yielded and the plastic hinge formed.The internal force of the models redistributed until failure.For the two test models with different reinforcement ratios,the crack load of model Ⅰ was smaller than that of model Ⅱ when the load and the boundary conditions of the two models were identical.(3)The shearing force of continuous composite girder with corrugated steel webs are mainly undertaken by the steel webs and almost all the stress of webs is shear stress.Therefore,the continuous composite girder with corrugated steel webs are easy to cause buckling.First of all,based on the theory of buckling and the failure mode of the two test models,it was analyzed that under normal circumstance,the buckling failure will not happen.Then in ABAQUS finite element analysis,the effect of concrete strength,reinforcement ratios and the thickness of steel webs on the buckling of continuous composite girder with corrugated steel webs were analyzed.With the increase of concrete strength and web thickness,the buckling bearing capacity of-composite box girder will be enhanced,and the influence degree and law of ordinary reinforcement ratio on buckling bearing capacity is not obvious.