Research On Mechanical Properties And Design Method Of Cold-Formed Thin-Walled Steel Closed-Assembled L-Shaped Axial Compression Members

The cold-formed thin-walled steel(CFS)closed-assembled L-shaped compression member is composed of two basic components joined together by self-tapping screws.This paper presents an experiment and finite element analysis(FEA)of the static mechanical behavior of the built-up components.The bearing capacity of the components was verified using the effective width method(EWM)and the direct strength method(DSM).Based on the calculation results of the EWM,a proposed calculation method suitable for calculating the bearing capacity of the CFS closed-assembled L-shaped axial compression member is presented.The specific work is as follows:(1)The experiment was carried out on 18 CFS closed-assembled L-shaped members with different parameters.The design scheme,test device and failure mode of the test piece are introduced,and the test results are compared and analyzed.(2)The FEA software ABAQUS is used to simulate the test specimens.A finite element model is established based on the measured dimensions and material properties of the test specimens,and taking into account the initial defects of the specimens and the nonlinearity of the model during the analysis.Then the analysis results are then compared with the experimental results to verify the accuracy of FEA.(3)The validated finite element model is used to conduct a more extensive analysis of the related parameters of the built-up components.The analysis results show that the slenderness ratio has a significant effect on the static mechanical properties of the specimens;As the heightthickness ratio of the web decreases,the ultimate bearing capacity of the specimen increases significantly,especially when the thickness is small,where an increases in thickness of 1/3 leads to an increases of approximately 65% in the bearing capacity;In contrast,the influence of screw connection distance on the static mechanical properties of the built-up components is not significant.(4)The axial compressive capacity of the built-up components is calculated using the EWM and the DSM respectively,and the results are compared and analyzed with the test and the FEA.It was found that,in comparison,the calculated values of the majority specimens were smaller than the test values and finite element values.Compared to the EWM,the bearing capacity values calculated using the DSW were closer to the test and finite element,with smaller errors.(5)Based on the results of the EWM calculation and in combination with relevant calculation methods in Chinese standards,a theoretical calculation method for the axial compression capacity of CFS close-assembled L-shaped members is proposed.Through comparison with the test and the FEA,it was found that the accuracy of the proposed method was good.