Experimental Research On Mechanical Properties Of Connection Joint Between Inclined Strut And Upright In Steel Storage Rack

The column plate of steel storage rack is a plane truss system which is connected by two columns and diagonal braces.The connection joint of braces and columns(brace-column connection joint)is often the weak part of the column plate and even the whole steel shelf.In practical engineering,the strengthening measures are mainly to change the cross-section form of braces and weld the thick plate.This thesis mainly studies the influence of spot welding thick plate on the mechanical properties of brace-column joints.Firstly,24 kinds of brace-column connection joints are designed according to the number of welding spot,the distance between welding spot and the thickness of thick plate.The axial tensile tests are carried out on the 24 kinds of connection joints and 72 test-pieces,and the test phenomena,load-displacement curve,load-strain curve and parameter influence of each group of specimens are detailed comparative analysis.Secondly,the three-dimensional finite element model of each test piece is established,and the strength of the welding spot is considered to be the design value of fillet weld and the equal strength value of parent material.According to the finite element results and test results,the bearing capacity,load-displacement curve,stress distribution and the influence of welding spot strength are compared and analyzed.Finally,the parametric analysis of brace-column joints is carried out,and the influence of the number of welding spot,the distance between the welding points and the thickness of the thick plate on the mechanical properties of the joint is studied.The design formula of the spot welding connection is obtained by modifying the design formula of the fillet weld strength in the code,which provides a reference for the application of this type of joint in the practical engineering.Through the above research,we can get the following main conclusions:(1)The strength of the connection joint in the side face of the thick plate is higher than that in the front.For the specimens with single side welding spots,the larger plastic deformation or direct fracture will occur in the welding spots,and the bearing capacity of the specimens with the same number of side welding spots is higher;(2)When solder joints are welded on both sides of the thick plate,the connection joint bearing capacity and the interaction between the thick plate and the diagonal brace are obviously improved.(3)When the strength of the welding spot is equal to the strength of the parent material,the finite element results are basically consistent with the test results,When the strength of the welding spot is the design value of the fillet weld,the bearing capacity of the joint is partial to safety;(4)When there are more than three welding spots at one end and the distance between the welding spots is three times the thickness of the thick plate,the interaction between the thick plate and the diagonal brace is the strongest;(5)The design formula of spot welding connection is applicable to the calculation of the number and distribution of the welding spots needed for the thick plate of the brace-column connection joint in the steel storage rack.