Research On The Local Buckling Behavior Of Cold-formed Thin-walled SHS And RHS Based On CSM

Local buckling is the deformation behavior of steel pipe components that needs to be avoided or utilized in the design.The current design specifications for steel structures refer to plastic deformation of the section in the component and the ability of which to resist local buckling.Therefore specifications divide the section into categories that exhibit different flexibility within a range of aspect ratios of plates,and use the corresponding bearing design.For the thin flexible section members with buckling bearing capacity less than the yield capacity,the “Effective Width Method” based on the edge yield of the plate subjected to post-buckling is usually used.Which failures to fully consider the plate-related effects and post-buckling plasticity development. “Continuous Strength Method” is a component design method based on section deformation and can effectively use steel strain reinforcement.This method is mainly applicable to non-thin section members,and has a relatively perfect theory in the bearing capacity design of stainless steel,high strength steel components.However,its application to cold-formed steels,thin flexible sections,and eccentric compressive loads remains to be studied.In this paper,comparing the experimental results of the finite element method and the collected data,the validity of the modeling method for the local buckling performance of the cold-formed square-rectangular steel pipe members which considering the initial geometric imperfection and the material nonlinearity is verified.The magnified parameter model was established by this modeling method.The influence of section softness,steel strength grade,section height-width ratio and the angle of action of eccentric pressure on the local buckling performance of cold-formed thin-walled rectangular steel pipe members was studied.The concept of equivalent strain was introduced.Based on the results of finite element method,the “Continuous Strength Method” was extended to the design of bearing capacity of cold-formed thin-walled rectangular steel tubes under axial compression,pure bending or eccentric compressive loads.The proposed “continuous strength method”for considering the section softness,aspect ratio and eccentric angle is proposed.The steel structure design specifications of China,Europe,and North America were applied to the examples,and the applicability of the national standard and continuous strength design methods to the calculation of the local buckling bearing capacity of a cold-formed thin-walled square rectangular section was analyzed.