Research On The Out-Of-Plane Effective Length Factor Of Brace In SHS Truss Using Gapped K-Joint

In HSS (Hollow Structural Sections) truss, the chords provide great restraints on the braces. So the effective length factor of braceμis less than 1.0. According to the Eurocode3, The effective length factor of brace of directly welded HSS truss is 0.75. However, the effective length factor of HSS truss is not specified in Chinese Code. In practice, HSS truss is supposed to be pinned. So it is necessary to do some research on the effective length factor of HSS truss. In this paper, a systematic parametric research on effective length factor of compression brace is carried out by ANSYS.Firstly, the compression brace is simplified as an axial compression member with elastic rotational restraints. According to stability theory of steel structures, the equilibrium differential equation is established. From the equation, the stability formula of compression brace is obtained. Then, the effective length factor of brace is obtained by stability formula and the Euler formula when the rotational stiffness is available.Secondly, the FE model of gapped K-joint is established. Then the out-of-plane rotational stiffness of the joint is calculated. Extensive FE analysis for out-of-plane rotational stiffness of the joint is conducted. Considering the parameters such asβ,γ,τ, g,η,θ, C, more than 300 joints are analyzed and the variation of rotational stiffness of the joint with geometrical parameters are available.Through the multi-parameter regressive analysis, equations calculating out-of-plane rotational stiffness of the joint are acquired. The out-of-plane rotational stiffness of the joint calculated from the equations coincide with the results that are obtained by finite element analysis.According to the stability formula of brace and the rotational stiffness of the joint, the effective length factor is calculated. The variation of effective length factor with the geometrical parameters is obtained. The equation calculating the effective length factor is acquired through multi-parameter regressive analysis.