Study On Axial Compression Performance Of Cold-Formed Thin-Walled Steel Geopolymer Foam Concrete Column

With the continuous development of green buildings,Cold-formed Thin-wall Steel(CFS)is gradually applied to low-rise and multi-storey residential buildings due to its advantages of energy saving,environmental protection,reasonable structure,light weight and high strength.However,existing studies have shown that CFS columns are prone to buckling under load,resulting in reduced bearing capacity.In addition,the geopolymer foam concrete made of solid waste is light in weight,energy-saving and environmentally friendly.Pouring it into CFS combined columns can limit the buckling of plates and give full play to their performance.The structural components composed of the two are used in low-rise residential buildings,which enriches the structural system of low-rise residential buildings,and is of great significance for the further study of light steel lightweight concrete structural system.Therefore,this paper systematically studies CFS-geopolymer foam concrete columns by combining experimental research,finite element numerical analysis and theoretical calculation.The main research results are as follows :(1)Firstly,the mechanical properties of geopolymer foam concrete were tested.Then,the axial compression tests of CFS single limb column,CFS combined column and CFS-geopolymer foam concrete composite column with C-section were carried out.The failure characteristics of the three columns were compared,and the load-displacement curve,load-strain curve and ultimate bearing capacity were analyzed.The influence of slenderness ratio on the axial compression performance of components was discussed.The main results are as follows :(1)The ultimate bearing capacity of the composite column is 1.4 times higher than that of the assembled column.(2)The ultimate bearing capacity of the three types of components decreases with the increase of slenderness ratio.(3)The lateral displacement of the composite column is smaller than that of the assembled column,indicating that the internally filled geopolymer foam concrete has a positive effect on suppressing the buckling deformation of CFS.(2)Using ABAQUS finite element analysis software,the finite element model is established,the correctness of the model is verified,and the variable parameter analysis is carried out.The main results are as follows :(1)The bearing capacity of the composite column is greatly affected by the slenderness ratio;when the slenderness ratio of the combined column reaches 45.44,it changes from local buckling to overall buckling.(2)The ultimate load of the combined column and the composite column decreases with the increase of the width-thickness ratio.When the width-thickness ratio of the board is in the range of60-100,the utilization rate of geopolymer foam concrete is higher;the internally filled geopolymer foam concrete can delay the local buckling of CFS plates,and the larger the width-to-thickness ratio,the more obvious the effect.(3)Increasing the number of solder joints can improve the ultimate load of the combined column.When welding the composite column,only the structural requirements are considered to ensure the stable connection of the two limb columns.For every grade increase in the density of foamed concrete,the ultimate load of CFS composite columns increases by about 1.5 %.(4)From the point of view of the amount of steel,the improvement of the ultimate bearing capacity of the composite column is more obvious by setting the symmetrical single rib.The setting of stiffeners increases the axial stress of geopolymer foam concrete,thereby increasing the ultimate load of CFS-geopolymer foam concrete composite columns.(3)The ultimate bearing capacity of the composite column was calculated according to the calculation methods in the ’ Code for Design of Composite Structures ’(JGJ138-2016),the ’ Load and Resistance Factor Design Specification for Structural Steel Buildings ’(AISC-LRFD),the ’ Recommendations for Design and Construction of Concrete Filled Steel Tubular Structures ’(AIJ)and the ’ Technical Code for Concrete Filled Steel Tubular Structures ’(GB50936-2014).It is found that the calculation method given in the ’ Code for Design of Composite Structures ’(JGJ138-2016)can roughly estimate the ultimate bearing capacity of the composite column.Based on the calculation method given in the ’ Code for Design of Composite Structures ’(JGJ138-2016),a calculation method suitable for the axial compression bearing capacity of composite columns is further proposed,and the accuracy of the formula is verified.