Experimental Study On The End Connection Performance Of Prestressed Concrete Composite Slabs With Steel Tube Trusse

Construction industry is an important pillar industry,the construction industry labor resources are decreasing,the cast-in-place construction technology malexposure,constantly pushing the construction industry to develop in the direction of industrialization,the prefabricated building structure system has been taken seriously by people.As a new type of floor slab,precast concrete composite slab has been widely used because of its advantages of high stiffness,good integrity and good seismic performance.At present,reinforced truss concrete composite slab is the most widely used,but there are still some defects,such as large plate thickness,easy cracking,more supports,and the need to set the post pouring belt at the joint joint.Based on these defects,this research group proposes a new type of steel tube truss prestressed concrete composite slab,and studies its mechanical properties.The results show that it has the advantages of high stiffness,good cracking resistance and good overall performance.Moreover,because of its thin prefabrication and good stiffness,it can reduce the total thickness of composite plate,reduce the vertical support in construction,shorten the construction period greatly,and has a good application prospect.At present,the prestressed concrete composite slab prefabricated bottom plate of steel pipe truss usually has a short anchorage rib-beard rib at the end,which has problems such as inconvenient production,construction and transportation.In order to solve the above problems,the research group proposed to cancel the traditional short rib at both ends of the prefabricated bottom plate,namely beard rib,and adopt the indirect lap reinforcement instead of the end anchorage connection form.In order to study the mechanical properties of this kind of end joint,this thesis mainly considers the length of the end joint reinforcement,the structure form of the superimposed surface,the thickness of the superimposed layer and other factors,and designs and makes eleven concrete composite plate specimens for static loading test,and uses the finite element software ABAQUS to conduct nonlinear simulation analysis of the mechanical properties,and analyzes the relevant influencing factors.The research results show that under the premise that the reinforcement ratio of indirectly bonded steel bars meets the minimum structural requirements of the code,the influencing factors have different degrees of influence on the overlapping surface and mechanical properties of the composite plate specimens,which mainly include the following contents:(1)The end of the composite plate does not appear to break off or lack of anchorage on the composite surface near the simply supported end support,and the anchoring form of the end and strengthening measures have no obvious influence on the simply supported end support.(2)The main conclusions are as follows: Increasing the length of lapped steel bars can improve the mechanical properties of indirect lapped steel bars,and the anchorage length of15 d can ensure the yield of indirect lapped steel bars;The bonding properties of the end and the anchoring properties of the end can be enhanced by removing the indirect lap bar from the surface of the bottom plate and setting the connection strengthening measures(keyway,shear bar).The thickness of the superimposed layer has a great influence on the mechanical performance of the superimposed surface and the anchorage performance of the end.With the increase of the thickness of the superimposed layer,the degree of the superimposed surface’s release decreases and the release becomes later.When the superimposed layer meets the requirement of a certain thickness,it is feasible to use indirect lap reinforcement for anchorage at the end,and the shear reinforcement can be appropriately configured to improve the adverse effects of indirect lap reinforcement on the superimposed surface.(3)The roughness of the superposed surface has a great influence on the mechanical performance of the superposed plate,and if it is not handled properly,it will easily lead to the superposed surface detachment,and then affect the anchoring performance of the end.