Experimental Study On Joint Working Performance Of H-steel Reinforced Concrete Slabs

With the development of social economy,the demand for production and living space is getting higher and higher.Although the reconstruction of buildings can meet the large span and large space that people need to produce and live,it will cause great waste.Therefore,the methods of reinforcement and reconstruction of existing buildings are generally accepted.This method can solve problems through less investment and shorter time.The improvement of the function of the old buildings is a common phenomenon,but the biggest problem of the function lifting is the change of the floor load.If the floor load is greatly increased,the load and deformation of the original floor design will not be satisfied.Therefore,the original floor must be properly reinforced.There are many ways to reinforce the floor,but when the load on the floor is larger or the span of the floor is larger,it can be strengthened by adding beams under the plate to reduce the span of the plate so as to reduce the internal force of the plate.The H type steel beam is added to the soffit.By taking some measures,it is the simplest reinforcement method to make the concrete plate and H steel form composite beam structure.But at present,the practical engineering reinforcement design does not consider the joint work of the H type steel beam and the concrete slab,only to be designed according to the steel beam.The reason is that the force performance of the composite structure has not been systematically studied.In this paper,12 post forming H-steel reinforced concrete slabs are made,which are connected by bolts and concrete slabs to form integral members(composite beams).The connection way between the steel beam and the concrete slab is as follows: the steel beam and the floor slab are connected through the bolt,and the bolt directly passes through the floor to connect the concrete slab and the steel beam.Different implant depth are considered in the planting bolt connection.The two connection methods also considered the number of anchor bolts(anchor spacing)and the way of joint surface treatment.Through static load test,the mechanical behavior of the composite beam structure is studied.The following conclusions are obtained through this study:1.The concrete slab is strengthened by using the steel beam.Through the use of the bolt connection or the bolt connection through the floor,the steel beam and the concrete slab can have a certain common working performance and form a composite beam,the bearing force is far greater than the bearing capacity of the steel beam.2.The composite beam specimens formed by the type steel beam reinforced concrete slab can be divided into four stages from loading to failure: elastic stage,cracking stage of concrete slab,sliding stage of the joint of steel beam and concrete,and failure stage of the specimen.3.Under the load,the joint surface of the steel beam and the concrete slab will produce micro cracks and slip,but the specimen does not lose the bearing capacity.At this time,the bolt connector bears the shear force at the joint surface.The steel beam and the concrete still have a certain overall working performance,but the stress distribution of the cross section and the force machine of the specimen is changed,the steel beam should not only bear the overall bending moment,but also bear the local bending moment.4.Finally,the component is damaged due to the failure of the bolt connector.For members with less depth of bolt,they may also be damaged due to the anchor bolt being pulled out of the steel beam and breaking away from the concrete slab.For members that connect through floors,such as bolt holes are not filled,it may also damaged by the relative slip and deformation of steel and concrete slabs.About the component that the bond between the steel and the concrete plate is sticked with the structural adhesive and the anchor bolt connection is relatively small,the bond between the steel beam and the concrete plate plays a major role,after the bond is destroyed,the anchor bolt is quickly cut off and damaged.5.The application of structural adhesive to the joint surface will delay the appearance of micro cracks on the joint surface and enhance the overall performance of the component.6.The torque exerted on the nut is affected by the magnitude of pre tension.The pre tension force of anchor bolt connections is large,and the bearing capacity of components is small.The reason for the analysis is that the anchor bolt is affected by the tensile stress before the load because of the pretension.When the specimen is loaded,the anchor bolt is subjected to shear stress,and the anchor bolt is destroyed by the joint action of tensile stress and shear stress,and the anchor bolt failure member is damaged.Therefore,the pretension is applied to make the structure be applied.The bearing capacity of the piece is reduced.7.The depth of implant has some influence on the bearing capacity of component.The depth of implant bolt is large,and the quality is easy to be guaranteed.There will be no anchorage failure.8.When the end of the steel beam is supported on the concrete beam,the concentrated load of the steel beam to the concrete beam should be considered,and the reinforcement measures for the concrete beam should be taken.9.With concentrated load on the upper part of the composite,the upper flange of the type steel beam will have local buckling instability,so if the concentrated load is acted on,the stiffener should be set at the position of the concentrated load at the position of the beam.10.When the concrete slab is strengthened with a steel beam,the steel beam and the concrete slab are formed through the setting of bolt connections,which can be calculated according to the composite beam,but the bearing capacity should be multiplied by a reduction factor,the reduction factor is recommended to take 0.85,and the number of anchor bolts should be properly increased.