Design And Optimization Of Commonly Used Sectional Cold-formed Steel Members And Structures

Cold-formed thin-walled steel structure has its advantages,such as high strength,easy to shape,thin wall,light weight,more flexible and diverse section,etc.It is found that the ultimate bearing capacity of cold-formed steel members can be improved by recombination and optimization design.At the same time,the optimized cold-formed steel members is applied to practical engineering,which can save the material and enhance the bearing capacity and reliability.This article mainly aims at the section size optimization of C-and Z-sections cold-formed thin-walled steel member and the stiffening angle of Z-section and lipped angle of L-section,.Then the optimized cross-section of the component is applied to the overall structure of the actual construction,and the optimization problem of the single-member-is extended to the optimization problem of the whole structure.A comparative analysis of the carrying capacity of low-rise houses and dome structures before and after optimization is proceeded.Firstly,the section optimization of C-and Z-sections cold-formed thin-walled steel member are carried out,that is,the cross-sectional area is selected,and the web,flange,rolled edge and thickness are optimized and combined for analysis.The main principle is the use of finite principle combined with genetic algorithm and direct strength method(DSM),The optimization procedure was programmed by Matlab in the axial compression conditions.At the same time,the different stiffening angles of the cold-formed Z-section with stiffening rib are optimized,the v-shaped stiffening angle is taken as the design variable,and the ultimate bearing capacity of the members is also taken as the objective function.It is found that the optimization of the Z-shaped members with v-shaped stiffeners is more effective than the ultimate load-bearing capacity of the non-stiffened members.Through the analysis of different cross-sectional dimensions and the same cross-section with different length of cold-formed lipped L-shaped steel member,it is found that the optimal lipped angle is 90 °,and also the shorter length of components,the less the buckling stress is affected by the change in lipped angle.Secondly,the optimized cold-formed thin-walled C-and Z-beams were applied to the composite frame of low-rise residential buildings.The critical buckling factors of residential structures under the same constant load,live load and wind load were analyzed,and it was found that the bearing capacity of Z-shaped steel frame after buckling was higher.Through the research on the wind direction angle under the weak bearing condition of the house,it is found that the axial force in the weak bearing area such as the eaves of the Z-shaped steel house is smaller than that of the C-shaped steel house.Finally,it is verified that the bearing capacity of the composite frame of the house with Z-shaped cross section is better.Finally,the dome structure established by a company in Ningbo is modeled and optimized.Using the corresponding optimization principle,the original double C-section steel member is transformed into the optimized single C-section with equivalent cross-sectional area,then add to the established 3d line model of the dome for buckling analysis and full-process stability analysis.The displacement and ultimate bearing capacity of the peak of the dome before and after optimization of the structure were compared.Finally,the optimized dome structure has the conclusion that the maximum deflection of crown is smaller and the bearing capacity is higher.