Study On Behavior And Design Method Of Cold-Formed Steel Box Built-Up Section Columns

Built-up columns are widely used in cold-formed thin-walled steel structure housing systems,which are generally arranged in the corners of the wall,door openings and other important parts,and are key structural components.Therefore,it is very important for the safety of cold-formed thin-walled steel structural systems to study the mechanical behavior of cold-formed steel double-limbed box built-up section columns and to study its ultimate bearing capacity.However,although some research results have been obtained on the mechanical properties of cold-formed thin-walled steel built-up columns,most of the domestic and foreign codes do not give the calculation method of its axial compression bearing capacity.Although a few standards have proposed relevant calculation methods,they are mainly based on the sum of the bearing capacities of the individual limbs.They have not been analyzed from the mechanical properties of the integral components and are not theoretically strict.Therefore,the study of the axial compression performance of coldformed steel box built-up section columns,and the proposed and improved design methods of such components have become a problem to be solved.In this paper,the Q345 cold-formed steel box built-up section columns as the research object,its axial compression performance and bearing capacity calculation methods have been experimentally studied and theoretical analysis,mainly completed the following aspects:(1)The experimental study on the axial compression performance of 32 cold-formed steel double-limbed box built-up section columns was completed.The mechanical properties,failure modes and deformation characteristics of the cold-formed steel box built-up section columns were investigated systematically.The influence of the slenderness ratio and the ratio of height to thickness on the stability of the components was studied.(2)The numerical simulation analysis of the axial compression performance and ultimate bearing capacity of the cold-formed steel double-limbed box built-up section columns was carried out.Firstly,based on the test results,the rationality of the finite element model was verified.Based on this,the variable parameters analysis of the axial compression stability of the cold-formed steel double-limbed box built-up section columns was performed using the finite element simulation method.The influence of the slenderness ratio and the ratio of web height to thickness on the bearing capacity of the component was further discussed.(3)The calculation method of axial compression bearing capacity of the coldformed steel box built-up section columns was completed.The following work has been done: Firstly,the ultimate bearing capacity of the cold-formed steel box built-up section columns was calculated according to domestic and international regulations,and compared with the test results to evaluate the practicability of the existing standard calculation methods for the double-limbed columns.On the basis of this specification,using the effective width method,a calculation method for the ultimate bearing capacity of the cold-formed steel double-limbed box built-up section columns was proposed.