Experimental Research On Mechanical Properties Of Connection Joint Between Upright And ?/C Type Beam In Steel Storage Rack

With the booming social economy in China,the demand for safe storage of goods and efficient operation in various industries is increasing,and the demand for steel shelf structure is also increasing.As a new type of beam,?/C beam has its unique advantages and has been widely used in steel storage rack.However,relevant research on the connection joint between this type beam and upright can hardly be found in the academia.The study of connections joint between upright and ?/C type beam in this paper can provide guidance for the application of this type of beam in practical engineering.There are two types of connections joint between upright and ?/C type beam that are currently used: the beam through-length connection joint and the beam disconnected connection joint.This paper will discuss the mechanical properties of these previous two types of joints,as well as three different types of enhanced disconnected connection joint whose stiffness and bearing capacity have been significantly improved.Firstly,the double cantilever beam test method is used to carry out the lowcycle reversed loading experiment of the joints,and the test data are analyzed in detail.The mechanical properties of the joints,such as bearing capacity,flexural stiffness,ductility and energy dissipation are studied.Secondly,the finite element model of the joints is established and simulated,and the mechanisms of joints under bending moment is further studied in combination with the experimental phenomena.Finally,parametric analysis is carried out to study the influence of upright thickness,beam thickness,bolt end spacing,bending plate thickness and bolt size on the mechanical properties of bending plate reinforced joints,which provides a reference for the application of this type of joints in practical engineering.Through the above research,the following main conclusions can be drawn:(1)The mechanical mechanism of connections joint between two types of beam and upright under bending moment is basically similar.The experimental phenomena,failure modes and stress distributions of the two types of joints are similar,but the bending stiffness,ultimate bearing capacity and total dissipated energy of the connections joint between ? type beam and upright are larger due to the larger bolt hole spacing and the existence of longitudinal stiffened rib on web plate.(2)The mechanical properties of the beam disconnected connection and the beam through-length connection are quite different.In beam disconnected connection,the distribution of stress in the flange of the beam is relatively small during the loading process,which basically does not play the role of resisting bending moment,resulting in the smaller bending stiffness and ultimate flexural capacity of the beam disconnected connections.The flexural stiffness and ultimate flexural capacity of the beam through-long joints are larger,but after the compressive buckling of the flange of the beam,the flexural bearing capacity of the joints will decline rapidly and the ductility of the joints is poor.(3)Three kinds of strengthening measures can effectively improve the bending stiffness and ultimate bearing capacity of the beam disconnected connection,and have little effect on improving the seismic energy dissipation capacity of the connections.The three strengthening measures have effectively limited the rotation of the beam in the joint area,fully exerted the role of the flange of the beam in resisting bending moment,significantly improved the stiffness and load-carrying capacity of the joint,but did not change the essence of force transmission between the members in the joint through shearing.The bolt hole wall is prone to plastic deformation due to extrusion,and its seismic energy dissipation capacity is poor.(4)Increasing the thickness of beam and bolt size can effectively improve the flexural rigidity and ultimate bearing capacity of bending plate reinforced connection,but with the increase of the bolt size,the improvement effect decreases gradually;Increasing the bolt end spacing of beam has obvious effect on the ultimate bearing capacity of joints,but has little influence on the bending stiffness of joints;and the thickness of upright has little effect on the mechanical properties of joints.(5)When the thickness of the bending plate is thin,the failure mode of the bending plate reinforced connections will be changed.The economic thickness of the bending plate is 1.25 times of the thickness of the beam.When the thickness of the bending plate is thin,it is easy to produce "bulging" deformation during the loading process,and the bending plate will be damaged before the beam,which will have a negative impact on the bearing capacity of the joint.When the bending plate can well restrict the rotation of the beam in the joint area,the effect of increasing the thickness on further improving the stiffness and bearing capacity of the joint is very small.