Research On The Bearing Capacity And Optimization Design Of Cold-Formed Thin-Walled C-Shaped Members

In recent years,the technology and products of cold-formed thin-walled steel structure have been developed rapidly in China’s construction industry because of its green,efficient and convenient construction characteristics.Prophase research found that the cross-section design of cold-formed thin-walled steel C-shaped members used by domestic light-weight steel housing production enterprises are modeled on the cross-section commonly used in foreign countries,and the cross-section form is single.This common cross-section form is not necessarily the one with the highest bearing capacity in the C-shaped members,which may lead to the low utilization rate of cold-formed thin-walled steel structure design materials and is not economical.Therefore,the research focus of this paper is to compare the bearing capacity of cold-formed thin-walled C-shaped members with different cross-sections when they only bear axial compression,axial compression and transverse uniform load,to study the influence of different cross-sections on the bearing capacity of members,and to set V-shaped stiffeners in the middle of member webs to study the influence of stiffeners on the bearing capacity of members.The main work is as follows:(1)Compiling MATLAB calculation program,according to the current specifications and general calculation methods,carrying out theoretical calculation on the bearing capacity of members with different cross-sections and automatically optimizing the cross-sections.The optimization results show that the calculation results of direct strength method may be more in line with the real response of members under axial compression load for general section forms;The shorter the curling length,the easier it is for members to have distortion and integral buckling.The higher the web height(h)is,the more likely it is for members to buckle locally and globally.When 1 < h/(a + b)< 2,the bearing capacity of the member is higher.The load-bearing capacity of members can be greatly improved after V-shaped web stiffening.(2)Through the axial compression test of the optimized section with high bearing capacity,it is found that the failure modes of the specimen are mainly related to the local bulging of the web and the whole bending around the weak axis,and the distortion failure of the flange and the curling combination.Setting a V-shaped stiffener can significantly improve the bearing capacity of the specimen.Through the finite element simulation of axial compression test,the accuracy of the finite element calculation method is verified,and the trend of ultimate bearing capacity of each specimen under axial compression test is in good agreement with the trend of theoretical optimization results and finite element calculation results.(3)In the low-rise cold-formed thin-walled steel residential system,there are basic components that bear both axial compression load and transverse load.According to the calculation method in the code,the program is written to calculate the theoretical bearing capacity of components with different cross-sections and optimize the cross-sections.Combining the theoretical and finite element calculation results,if the components bear the combined action of axial pressure and asymmetric bending moment in the plane,when h≈(a+b),the bearing capacity of the member is higher.If the member is subjected to axial compression and bending moment in symmetry plane,when h ≈ 1.5(a+b),the bearing capacity of the unstiffened member is higher,when h≈2(a+b),the bearing capacity of the stiffened member is higher.With the same amount of materials(that is,a certain cross-sectional area),and considering the influence of different geometric parameters of the cross-section,the cross-section with the highest ultimate bearing capacity and the best comprehensive performance is selected.In practical engineering application,it can obviously reduce material utilization and optimize product comprehensive performance;Or make the design of the structure more reliable without changing the arrangement form of the structure.