| In the cold-formed steel(CFS)portal structures,the bolt connected beam-to-column joints prone to feature as the semi-rigid joint.The performance of the joint will affect the transverse stiffness and overall stability of the structure.In this paper,the finite element method(FEM)is used to investigate the load resistance capacity of the CFS beam-to-column joint,and the primary motivation of the study is to provide a guide to the future design of such joints.Founded on the theoretical analysis,the initial rotation stiffness of the group bolt joint can be considered as the vector combination of the initial tensile stiffness of single bolt lapped joint.It is also found that the initial tensile stiffness of the single bolt lapped joint will be influenced by shell thickness,bolt-hole tolerance,shear surfaces and layer numbers.Therefore,a series of parametric studies are conducted to achieve the design formula for initial tensile stiffness and to further propose the prediction model of the initial rotation stiffness of the beam-to-column joint.Optimized suggestion of the initial rotation stiffness is also presented by comparing the factors like bolt number,clear distance,sectional configuration and shell thickness.Moreover,strength of the beam-to-column joint is also studied numerically.The relationship between the factors and the failure modes and the ultimate load is presented herein.The result shows that the maximum service efficiency can be obtained when the thickness of the gusset plate is 1.5 times over supported members or the bolt distance is 1.5 times greater than the web depth.The moment to local pressure and moment to shear combinations are also considered in the study to investigate the ultimate capacity,failure modes and moment transfer coefficient.Optimum design suggestions are further presented according to the conclusions. |
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