Experimental Study And Analysis Of Joints Connected By U-connector And SHS With Self-tapping Screw

The steel tube structure has been widely used due to its superior performance.The design of joints is the key to the structural design of steel tubes.In this paper,a new type of joint is studied,which is made up of U-connectors with different indentation and holes on it and square steel pipe connected by the self tapping screw.It has light weight,easy connection,flexible use,short construction period,high degree of assembly,environmental pollution and other advantages,where the design of the same hole on the U-connector take into account the possibility of changing the angle of the web rod,which is very convenient for engineering applications.In this paper,the joint connected by U-connector and SHS with self-tapping screw joint of square steel pipe is studied.The force performance of the joint is studied by the test and the finite element method,the concrete work is as follows:By changing the indentation arrangement on the U-shaped connector,four Ushaped connectors were designed: plate-type connectors,punched-type connectors,transverse wave-type connectors,and longitudinal wave-type connectors.Four types of joints using four kinds of connecting pieces and square steel pipes connected by self-tapping screws are used as research objects.The reaction force frame is designed and the full-scale test of the joints is performed.The mechanical properties of the joints are tested,such as strain and deformation,and the ultimate bearing capacity and failure form of the joints are obtained.On this basis,using the finite element software ABAQUS to conduct nonlinear analysis of the test joint,and compared with the experimental results,the results are in good agreement,verifying the correctness and rationality of the finite element modeling method.The research shows that the ultimate bearing capacity of different U-joints is not much different,but there is a big difference in node failure mode.The ultimate bearing capacity of joint depends on factors such as the material selected,the geometric dimensions and the cross-sectional area.The failure mode of the joint is related to the out-of-plane stiffness of the Uconnector.The main failure modes of the joint specimens are: excessive deformation of U type connections,local buckling of chord and overall bending and buckling of the chord.Based on the precise finite element modeling method of joints,,without changing the mode of action of the load,analyzed the stress performance,damage form and ultimate bearing of the transverse wave joint by the four factors that affect the state of the chords,the ratio of the diameter and thickness of the chord,the ratio of the ratio of the web to the chord,the ratio of the thickness of the U-connector to the chord,and the ratio of length of chord to U-connector.The results show that the stress of the chord will weaken the bearing capacity of the joint,and the different chord thickness will have a great impact on the bearing mechanism,the ultimate bearing capacity and the damage form of the joint.The research results in this paper will be helpful to the popularization and application of the steel tube structure made of U type connections and square steel pipes connected by self-tapping screws.