Study On Axial Compression Performance Of Cold-formed Steel Composite Walls With Infilled Lightweight EPS-Gypsum Based Material

With the development of the cold-formed steel(CFS)residential structure system from low-level to mid-rise or high-rise,CFS composite walls as the main force components,is required for higher requirements on its axial compression performance.Compared with the traditional CFS wall,the CFS composite wall with infilled lightweight EPS-gypsum based material(LEGM)is an innovative wall,filling composite lightweight materials including industrial waste polystyrene(EPS),desulfurized gypsum and other raw materials,which can significantly improve the thermal insulation,fire prevention and sound insulation of buildings,and also increase the overall stability and load-bearing capacity of composite walls.In this paper,the axial compression performance of CFS composite walls with infilled LEGM is investigated through experimental research,numerical simulation and theoretical analysis methods,and a proposed design method is proposed.First of all,axial compressive loading test on four full-scale specimens including one unfilled wall and walls filled with three different strength grades of LEGM,were carried out to investigate the axial compression performance of CFS composite walls.The test equipment,test methods,failure process of specimens,analysis of test data were introduced,and the working mechanism and failure mode of CFS composite walls with LEGM were analyzed.The test results show the failure mode of unfilled specimen was local buckling of studs,and final crippling at stud ends,whereas for the infilled walls,it was strength failure of stud cross-sections.Compared with the unfilled wall,the axial bearing capacities of the infilled walls were significantly increased,with the enhancements by 1.88~2.99 times.With the increase of the compressive strength and density of infilled gypsum based material,the axial bearing capacity of the walls accordingly increased.The encased wall studs were in or close to yield states.Secondly,finite element method based on ABAQUS program considering geometric large deformation,materials and boundary nonlinear was used to simulate the tested speimens.It was found that the results of finite element models and experiments are in good agreement,which verify the correctness of the numerical model and the feasibility of numerical analysis.Based on the verified finite element models,parameters analysis was carried out to mainly determine the effects of the number of studs,wall thickness,thickness of steel cross-sections,and LEGM strength on the axial performance of composite walls.The results show that increase the number of studs,wall thickness,steel thickness and LEGM strength,the axial compression bearing capacity of the CFS composite wall with infilled LEGM also increased.Finally,based on experimental research and finite element analysis,a calculation formula for the axial bearing capacity of CFS composite walls with infilled LEGM,considering the coefficient α of reduction of the bearing capacity of CFS columns and the LEGM correlation coefficient η is proposed.The reduction coefficient α is suggested to be taken as 0.9 and the LEGM correlation coefficient η proposes two calculation methods.Through comparison and verification of the results of that obtained from the proposed and numerical investigations,it is recommended to adopt the multiple linear regression formula that takes into account the composite action of different influencing factors.