Research On The Mechanical Properties Of Close-fitting Steel Tube Truss Concrete Composite Floo

Steel tube truss composite floor refers to a kind of floor formed by pouring concrete on the precast bottom plate of grouting steel tube truss.Because of its advantages of thin bottom plate,high stiffness of bottom plate,light weight and high bearing capacity,it has been widely used in the assembled floor system.At present,some new joint structures have been proposed by scholars at home and abroad.However,the joint structures widely used in practical engineering are mainly the traditional post-cast belt joint,and there is a relative shortage of joint structures that can realize both tight joint and bidirectional plate force transfer.Therefore,it is of great research significance to pay attention to the more reasonable new lateral tight joint structure and improve the bi-directional mechanical performance of tight laminated floor slab to improve the prefabricated floor system and promote the development of the prefabricated building industry.Based on the spaced groove joint structure proposed by the research group,which is exempt from the influence of reinforcing bars protruding from the side of the soleplate,this thesis adopts the method of combining experimental research and finite element simulation to study the mechanical performance of concrete composite floor with dense steel pipe truss,which provides relevant basis for the application of spaced groove joint structure in practical engineering.The main research contents are as follows:1.The static loading test was carried out on one post-poured laminated floor slab,five spaced recessed laminated floor slabs and one non-recessed laminated floor slab specimens,and the crack distribution and deflection changes of each laminated floor specimen were investigated.The test results of bearing capacity and reinforcement strain of each laminated floor specimen with different joint structures were compared and analyzed,and the stiffness and overall mechanical performance of each laminated floor specimen were studied.The influences of the parameters such as lap length,diameter,number of joints and distance between steel tube truss and plate edge are analyzed.The results show that all the laminated floor specimens exhibit obvious bending failure characteristics.The spaced groove structure can meet the requirements of integral joint and improve the distribution pattern of floor cracks.Increasing the lap length and reinforcement ratio of split-joint rebar can improve the bearing capacity and overall mechanical performance of floor specimens.The distance between steel tube truss and slab edge has no obvious effect on the stiffness and bearing capacity of floor specimens.2.Using ABAQUS software,finite element analysis was carried out on the specimens of post-cast laminated floor slab and spaced recess tightly packed laminated floor slab.The crack distribution,bearing capacity and reinforcement strain distribution of the laminated floor slab were investigated,and the simulation results were compared with the test results to verify the accuracy and rationality of the finite element model.Then,based on the finite element results,the refined parameter analysis of the spaced-groove laminated floor was carried out to study the effects of the lap length and diameter of the joint reinforcement,the distance between the steel tube truss and the edge of the slab,and the strength of the poured concrete on the mechanical properties of the tightly packed laminated floor.The results show that the ultimate bearing capacity of the composite floor can be obviously improved by increasing the lap length and diameter of the jointed reinforcement in a certain range.The distance between steel tube truss and slab edge has certain influence on the bearing capacity and stiffness of composite floor.When the distance between steel tube truss and joint is too large,the bearing capacity and stiffness of floor will decrease.Increasing the strength of the post-cast concrete can improve the bearing capacity of the composite floor,but when the strength of the post-cast concrete exceeds40 MPa,the bearing capacity does not improve significantly.3.Based on the test results and finite element analysis results of the spaced recessed laminated floor slab,combined with the processing of the spaced recessed laminated floor slab,the difficulties in the manufacturing process of the spaced recessed laminated joint structure were analyzed,and the relevant design suggestions and construction requirements were put forward to provide reference for its application in practical engineering.