Research On Compressive Behavior And Design Method Of Novel Cold-Formed Steel Built-Up Closed Column With T-Shaped Section

With the continuous development in the field of “green building”,the cold-formed steel(CFS)structural system has been widely used in the construction industry,especially abroad.As the main load-bearing members,the cold-formed steel built-up members have been widely concerned by scholars at home and abroad.In this paper,a novel cold-formed steel built-up closed column with T-shaped section is proposed.The T-section built-up closed column can not only have advantages of large torsional stiffness and section moment of inertia,which are the characteristics of the traditional closed section,but also can directly be connected to the wall panels in two directions without adding C-section steel,like the traditional open section.The axial compression performance is investigated by axial compression test and finite element numerical models.Refering to the calculation methods of the ultimate axial bearing capacity in the existing codes,the proposed calculation method for the ultimate axial bearing capacity of the T-shaped built-up closed column is proposed.The specific work is as follows:(1)The experimental investigated was completed,and 18 T-shaped built-up columns with different parameters were compressed axially.The section form,test setup,test method and test phenomena of specimens were introduced in detail.The test results of T-shaped built-up closed columns were compared and analyzed.(2)Based on measured dimensions and actual boundary condition of test specimens,the finite element method models of the test specimen were established using the software ABAQUS.The finite element results were summarized,and the finite element results are compared with the test results to verify the reliability of finite element method models in this paper.(3)Based on the reliability of the numerical models,in order to investigate the influence of the slenderness ratio,the height-thickness ratio of the web and the screw spacing on the axial compression performance of the T-shaped built-up closed columns,the variable parameter analysis of the above factors of T-shaped built-up closed columns were carried out.The results showed that reducing the slenderness ratio and the height-thickness ratio of the web can significantly improve the axial compression performance of T-shaped built-up closed columns.When the spacing between screws was changed from 150 mm to 450 mm,it can have little impact on the ultimate axial bearing capacity and failure mode of the specimen.(4)The ultimate axial bearing capacity of the test specimen and the finite element specimen can be calculated by using the calculation methods in the Chinese code GB50018-2002 and the American AISI code,respectively.The results showed that comparing to the test results and finite element results,the effective width method(EWM)in the American AISI code was relatively conservative.On this basis,the calculation method in the existing codes was modified by multipling a factor,and the suggested calculation method for the ultimate axial bearing capacity of the T-shaped built-up closed columns was proposed,and its accuracy was verified.