Experiments On Double Limb Channel Steel Built-up Open Sections With Complex Edge Stiffeners And Web Holes Under Eccentric Compression

Cold-formed steel(CFS)members have been widely used in low or multi-rise residential and commercial construction due to its flexible and efficient cross-section and good structural behavior.With the development of production capacity and the gradual maturity of technology,the cross-section shapes of cold-formed thin-walled steel members are more complicated and diverse.In order to meet the requirements of different layout and higher capacities of the actual building construction,the built-up sections formed by connecting two or more single members together become a new trend.At the same time,considering the convenience of installing electrical,plumbing and heating facilities,perforations become a common phenomenon in cold-formed steel structure.However,perforations cause the reduction of structural stiffness and make the stress distribution around the hole more complicated.It also has a significant influence on the buckling behavior and ultimate load-carrying capacity of the columns.Therefore,the structural behavior about perforated cold-formed built-up I section beam-columns with longitudinal web and complex edge stiffeners is necessary to be tested.A total of eight built-up open section columns were tested subject to eccentric compression.The single limb contained two section shapes with web holes,lipped channel with complex edge stiffeners and ?-shaped section with complex edge stiffeners.The bearing capacity and bucking mode were studied.Finite Element Analysis(FEA)was carried out to simulate the eccentric compression tests by ANSYS,and it was verified by experimental results.The influence of load eccentricity,plate thickness,flange width,web height,hole height,hole width and hole shapes on the structural behavior of built-up I section beam-columns is analyzed by ANSYS.A finite element analysis was carried out on perforated cold-formed built-up I section beam-columns with longitudinal web and complex edge stiffeners.The results show that the stiffeners on the web can increase the ultimate load of built-up section beam-columns within a certain eccentric load range,while,which has limited improvement on the bending stiffness of the specimen around the weak axis.If the bending moment is excessively larger the difference in the two kinds of cross-section members is gradually reduced.However,the failure modes do not change with the increase of eccentricity,the failure mode of double limb channel steel built-up open sections with complex edge stiffeners and web holes(DC1-section)is the interaction of local,distortional and overall flexural buckling;The failure mode of double limb ?-shaped channel built-up section with complex edge stiffeners and web holes(DC2-section)is the interaction of distortional and overall flexural buckling;According to above literature review,it is necessary to carry out the experimental study and finite element analysis on perforated cold-formed built-up I section column with longitudinal web and complex edge stiffeners.In addition,the current domestic andinternational related regulations do not clearly define the ultimate bearing capacity of the double-limbed section beam-column with holes.Therefore,based on the existing direct strength method calculation formula of single-limb beam-column with holes,the calculation formula of bearing capacity of built-up section members with holes is proposed.Applicability of above formulas were verified well and could be used as a reference for related researchers and designers.