In this paper, the torsional moment of the right-angle fastener bolt is taken as the main research parameter, and the torsional stiffness performance of the right-angle fastener under different working conditions is studied experimentally. By establishing the moment–rotation relationship model of the node, the mechanical performance and rotation characteristics of the semirigid connection of the node are studied. According to the joint stiffness value determined by the experimental study and the theory of semirigid connection frame with lateral displacement, the calculation formulas of the stiffness correction coefficient αu of the transverse bar and the constraint coefficient K at the end of the vertical bar are derived, and the effective length coefficient μ of the vertical bar and the theoretical value of the stable bearing capacity of the vertical bar under different working conditions are given. Compared with the current standard values, it is found that the theoretical calculation results of the percentage increase of the stable bearing capacity of the vertical bar are 3 to 4 times larger than the standard calculation results when the step distance is reduced. The theoretical calculation method can better consider the semirigid characteristics of the joint and the influence of adjacent members on the stable bearing capacity of the vertical bar.
The calculation method of steel pipe support in current specifications is not uniform, and it is unsafe to directly apply the stability coefficient of the vertical bar in the current code, which leads to frequent safety accidents of fastener steel pipe supports. Through the field statistics of the initial defects of the steel pipe, it is found that the initial bending values of the 3 m and 6 m steel pipes with the largest size are larger in L/400. The stability coefficient table is obtained by taking the initial bending of L/400 as the initial defect, which is 43.15% smaller than the stability coefficient given by the specification. Through the comparative analysis of the actual engineering monitoring results, the calculation results of the original specification and the calculation results after the correction of the stability coefficient, it is concluded that the stress calculated by the stability coefficient proposed in this paper is similar to the actual monitoring results of the project and is greater than the stress of the vertical rod calculated by the stability coefficient of the original specification. It is suggested that the corrected stability coefficient should be applied to the actual project.
Direct analysis method (DAM) is a second-order nonlinear analysis approach widely used for its high accuracy and simple flow. It is suitable for pinpointing the internal force response and nonlinear behavior of steel tubular scaffold with couplers (STSC), which has large initial defects arising from repeated use. This paper firstly quantifies the initial defects of steel tubes of the scaffold and draws the column curves of the tubes with different initial bending and residual stresses. On this basis, a reference value was derived for the overall initial defect of the tubes with different initial bending. Through a calculation example, a finite-element model was established in view of the overall initial defect, the initial defects of components, and the nonlinear semi-stiffness of nodes and the DAM flow was introduced for the STSC. The calculation example verifies the rationality of the reference value for the overall initial defect, making it easier to apply the DAM to actual engineering.
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