Study On Mechanical Performance Of Semi-rigid Joints Of Disc-buckled Steel Pipe Scaffold

Disc-buckled steel pipe scaffold(hereinafter referred to as " disc-buckled scaffold ")is widely used in construction because of its simple structure,large bearing capacity,rapid disassembly and strong versatility.By the end of 2022,in order to ensure the safety of housing construction and related municipal infrastructure,various ministries and commissions across the country have issued a number of policies to promote disc-fastened scaffold,and the requirements for its structural bearing capacity and safety performance have also increased.As an important part of the bearing capacity and stability of the structure,the mechanical performance of the joints is of great significance to ensure the smooth construction of the project and the safety of workers.At present,a large number of literatures at home and abroad have expounded the research methods and results on the performance of the disc-buckled joints,and show that the disc-buckled joints show typical semi-rigid connections.However,the relevant research content is about the determination of the stiffness value of the joints.The stiffness values obtained from different research results are different.In addition to the material factors,the depth of the pin wedge designed by the joint test schemes in different studies is different.The influence of the pin wedge tightness on the disc-buckled is ignored,and the pin wedge tightness of the neutral bar joints during the erection of the formwork is uncertain.The stiffness of frame joints is not a specific value but distributed in a certain range,so the stiffness data obtained from the test can not be used as a general conclusion to guide the construction.Therefore,in view of this situation,in order to fully obtain the influence degree of the pin wedge tightness on the semi-rigid joints of the disc-buckled frame,and to grasp the mechanical performance of the disc-buckled frame joints,this paper carried out the research on the semi-rigid joints of the disc-buckled steel pipe scaffold.The main research contents are as follows:1)By constructing the Φ48 type and Φ60 type disk buckle connection joint specimens,the torsional stiffness test of the joints under different wedge tightness is carried out.It is concluded that the vertical bar connection joint is a typical semi-rigid connection,but its rigidity degree is quite different.Through the quantitative discussion and analysis of the semi-rigidity of the joints,the influence degree of the wedge tightness of the pin on the initial torsional stiffness of the joints is obtained.Combined with the experimental phenomena,the reasonable range of the wedge tightness of the pin and the recommended value of the initial torsional stiffness of the joints are comprehensively determined.By using statistical nonlinear regression analysis,the relationship between the initial torsional stiffness of the connection joint and the wedge tightness of the pin is obtained.2)The coupling node model is established by mechanical analysis and finite element simulation of the disc-buckled steel pipe scaffold joint.According to the coupling model,the numerical relationship between the initial wedge tightening torque and the friction torque of the pin of the disc-buckled scaffold and the rod end torque of the semi-rigid node is obtained by statistical fitting,and then the complete simulation conditions of the node are obtained.The mechanism of the wedge tightness of the pin on the disc-buckled scaffold node is revealed,and the mechanical performance of the semi-rigid node of the disc-buckled steel pipe scaffold is described in detail.3)Aiming at the uncertainty of the wedge tightness of the bolt,the characteristics of the interval number theory and the convex model method of the set theory are used to solve the stiffness of the whole frame joint,and the finite element software is used to analyze the influence of the wedge tightness of the pin on the nonlinear ultimate bearing capacity of the disc buckle.Taking the basic lateral element of the lateral steel frame structure as the object,the deformation diagram is used to represent the overall buckling instability mode when the frame body reaches the ultimate bearing capacity.The importance of the wedge tightness of the pin to the structure is obtained by synthesizing the nonlinear ultimate bearing capacity under different wedge tightness,and the reasonable range of the wedge tightness of the pin proposed in this paper is further verified.