Study On Flexural Blucking Behavior Of Castellated Beam Web Considering The Effect Of Slab

For the castellated structure,the local buckling of the web is one of its main failure modes,and the buckling will cause a rapid increase of the local deformation of the web until the work is terminated,which may result in the overall instability of the member and the structural chain reaction.In the traditional steel structure design,the local buckling of the web is avoided by limiting the aspect ratio of the web.In the castellated structure,the inter-hole pier and its bridge are likely to have local buckling problems,which is more complicated than the solid members.At present,most of the researches on the local stability of castellated beam members are carried out around pure steel castellated beams,and there are few studies on castellated beams considering concrete slabs.Therefore,it is necessary to carry out experimental research on the flexural buckling performance of the webs with slab castellated beams.On the basis of the original three pure steel castellated beams,two castellated beams with cast slabs were designed and fabricated.The static test of these two castellated steel beam-concrete composite beams was carried out at the four points.By observing the location of buckling on the steel beam and the location and shape of the cracks in the concrete slab,the web buckling performance,bearing capacity,hole angle stress distribution and specimen ductility are analyzed,and compared with the test results of the non-floor pure steel castellated beam.After studying the increase of the slab and the stiffener between the webs,the influence on the failure mode,stress distribution and bearing capacity of the castellated steel beam specimens.The finite element software was used to establish the model for numerical simulation,and the test results were compared with the finite element simulation results to verify the accuracy of the model.Under the action of pure bending,the effects of different high-thickness ratio,vertical opening ratio and width-to-height ratio of the pier on the flexural buckling behavior and ultimate bearing capacity of the composite beam of concrete beam-concrete slab are investigated.It shows that the concrete slab on the castellated beam can greatly improve the bearing capacity of the specimen and improve the buckling performance of the web.The slab restrains the web at the upper flange position,so that the damage form and position change,and the buckling of the bridge plate is changed from the buckling of the upper wing edge to the bridge deck.The web height-thickness ratio has a significant effect on the buckling performance of the web.Reducing the web height-thickness ratio can improve the flexural buckling performance of the web,but has little effect on the ultimate bearing capacity of the specimen.When the aspect ratio is below 75,the strength failure occurs before the steady failure occurs.The vertical opening ratio has less influence on the castellated beam web considering the slab effect,although the buckling load increases as the opening ratio decreases,but the increase is small.The buckling load of the castellated beam with concrete slab increases with the increase of the aspect ratio of the pier,but there is a change of the failure mode and the failure position between the width and height ratio of 0.474 and 0.258,and the buckling around the edge of the hole near the loading point Flexing the web between the holes.