Research On Shear Performance Of U-shaped PBL Shear Connectors

In recent years,steel-concrete composite structures have developed rapidly under the prefabricated construction technology.Among them,the shear connectors at the key parts of the steel-concrete combination play an important role in the bearing capacity and deformation of the structure.With the further development of assembly construction,it is necessary to meet the high load-bearing shear connectors.Therefore,studying the mechanical properties of shear connectors is of great significance and engineering value.In this paper,the Twin-PBL shear connectors is optimized and a new type of shear connector structure(U-shaped PBL shear connectors)is proposed.And the experimental research on the influence factors of the ultimate bearing capacity of this kind of shear connectors is carried out.The main contents are as follows:(1)Based on the Twin-PBL shear connectors,an optimized structure of a new type of high load-bearing shear connectors(U-shaped PBL shear connectors)is proposed.The finite element modeling method is used to compare the difference in ultimate bearing capacity of the new shear connectors and Twin-PBL shear connectors,as well as the damage and stress of the stressed part.Studies have shown that the ultimate bearing capacity of the U-shaped PBL shear connectors is 40% higher than that of the Twin-PBL shear connectors under the condition of end bearing pressure;Under the condition of no end bearing,the ultimate bearing capacity of the new shear connectors is slightly smaller than that of Twin-PBL shear connectors.(2)Research on the mechanism of load transfer and bearing capacity improvement of U-shaped PBL shear connectors.A static push-out test of 16 shear connectors in 4sets of specimens was carried out.The test shows that the bearing capacity of the U-shaped PBL shear connectors under pressure at the end is significantly higher than that of the Twin-PBL shear connectors.In the early stage of the force,the shear force is borne by the bearing concrete corresponding to the end steel plate,and the end concrete gradually cracks,and gradually produces eight-shaped cracks;as the force increases,the shear force of the penetrating steel bars gradually increases,and cracks appear in the front concrete;When the ultimate bearing capacity is reached,the concrete cracks develop and are partially connected,the first penetrating steel bar yields,the pressure-bearing steel plate is bent,and the bottom weld is destroyed.The ultimate bearing capacity of the new shear connectors is mainly composed of three parts: the bearing concrete corresponding to the end steel plate,the penetrating steel bar and the concrete tenon.Compared with the Twin-PBL shear connectors,the increase in bearing capacity is mainly due to the shear force of the bearing concrete corresponding to the end steel plate.(3)Analyze the influencing factors of the ultimate bearing capacity of U-shaped PBL shear connectors.Analyze the parameters of the concrete strength grade,the diameter of the penetrating steel bar,the hole diameter of the steel plate and the end pressure,etc.The test results are compared with the ABAQUS finite element numerical simulation.Studies have shown that the strength grade of concrete has a greater impact on the ultimate bearing capacity of shear connectors.Changing the diameter of the penetrating steel bar and the diameter of the U-shaped steel plate has less impact on the ultimate bearing capacity of shear connectors.(4)Research on optimization of U-shaped PBL shear connectors structure.Combining the results of the push-out test and the finite element,the structure of the shear connectors is optimized,and its main stressed components are analyzed.The results show that the ultimate bearing capacity of the intermittently arranged new shear connectors can reach the carrying capacity of the twin-PBL shear connectors arranged in the full length;increase the center distance of the perforated steel plate rib,maintain the thickness of the pressure steel plate,and reduce the pressure steel plate The area can improve the continuity of the concrete inside and outside the U-shaped perforated steel plate,and make the shear force distribution more reasonable,thereby increasing the ultimate bearing capacity of the U-shaped PBL shear connectors.The main content and results of this article have reference value for further research on U-shaped PBL shear connectors,and provide a new idea for assembly construction of steel-concrete composite structures.