Behavior Of Channel-Casing Reinforced SHS X-Joints Under Out-Plane Bending

SHS X-Joints are widely used in building structures due to their excellent performance,especially in single-layer reticulated shell structures.The single-layer reticulated shell structure has high requirements on the out-of-plane bending resistance of the node,and usually needs local reinforcement to meet the needs of rigid nodes.However,the research on the mechanical properties of the out-of-plane bending of the other steel tube reinforced node is still not perfect.In this paper,SHS X-Joints in single-layer reticulated shell structures are taken as the research object,and two strengthening methods are proposed,mainly to analyze and study the mechanical properties and failure modes of the joints under out-of-plane bending.And,according to the analysis results,it put forward more reasonable construction suggestions and design methods for SHS X-Joints.Firstly,the out-plane bending tests include 3 unreinforced joints,2channel-casing reinforced joints and 2 lifted-channel-casing reinforced joints,the results show that:(1)the main deformation of the unreinforced joints is the plastic deformation of the chord,the cracking of the weld in the intersecting area of the chord and brace,and the cracking of the corner of the tension zone of the chord,with the increase of?,side wall of chord more involved deformation;(2)the failure forms of the channel-casing reinforced joints are the yield of the flange of the chord and the flange of the collar-plate,and the crack at the root of the brace;which of the lifted-channel-casing reinforced joints are the yield of the flange of the lifted channel plate,and the crack between the brace and the lifted channel plate.Both reinforcement schemes have a better optimization effect on the out-of-plane bending performance of the joints.Among them,when?=0.7,the moment resistance of the collar-plate is increased by 208%compared to the unreinforced joint,and the moment resistance of the lifted-channel-plate is strengthened to increase 236%,it can be seen that the reinforced node has greatly improved the bending capacity of the node due to the change of the original damage form and the force transmission path.Then use the ABAQUS software to establish the node finite element models,and compare with the test results to verify the accuracy of the models.On this basis,further analysis of the parameters of the channel-casing is in progress,the main parameters including brace-to-chord width ratio?,chord width to thickness ratio 2?,length of reinforcement plate l_p,lifted height of reinforcement plate h_p,thickness of reinforcement plate t_p and so on.The parameter analysis found that the key parameters affecting the strengthened nodes are ?,lp and hp.When ?<0.6,the main failure mode of the node is the yield of the channel-casing flange;when ??0.6,the main failure mode of the node is the crack of the weld between the brace and the channel-casing.Among them,when ??0.6,as the h_p or l_p increases,the moment resistance of the reinforced node gradually increases;when ?<0.6,the h_p or l_p has basically no effect on the bending performance of the joints.Therefore,the lifted-channel-plate reinforcement method is more suitable for nodes with ??0.6.It is recommended that the lifted height h_p be 30%?40% of the chord width,and the length of reinforcement plate is not more than twice the width of the brace.Finally,this paper explores the out-of-plane bending mechanism of the channel-casing reinforced joints and lifted-channel-casing reinforced joints:The channel-casing reinforced joints:the flange of chord and the flange of the channel-casing are cooperatively bent,and the flange side yields,the channel-casing protects the flange of the chord,and the damage form changes into the crack at the root of the brace;The lifted-channel-casing reinforced joints:the out-of-plane bending moment acts on the brace,the lifted-channel-casing protects the flange of the chord,the weak position of the node is transferred from the chord flange to the flange side of the lifted-channel-casing,and the failure mode changes to yield of the lifted-channel-casing flange.According to the failure mode of the reinforced nodes,the calculation formula of the moment resistance is proposed,the formula calculation results are in good agreement with the calculated and simulated values,with an average value of 0.9 and a variance of 0.0095.The paper has 48 pictures,14 tables,and 92 references.