Theoretical And Experimental Research Of Cold-formed Steel Residential Building Wall Stud System Subject To Centric Axial Loads

Light-gauge steel residence is a new type of residential building system which is composed of cold-formed steel frame and wallboard. Wall-stud system is composed of steel stud with plasterboard or OSB attached to both flanges of the stud with screws at regular intervals. It is the main vertical bearing structure in this system.The wallboard is simplified to elastic springs distributed continually along the axial direction of stud. The total potential energy equation of stud braced on both sides wallboard of different material and one side wallboard is established using energy principle. Displacement functions are introduced, which satisfy the end condition that the bottom is fixed and the top end is a roller support. The buckling load equation of stud braced on both sides wallboard of different material and one side wallboard is obtained using variation principleFinite element model is established to analyze the wall-stud system. Shell element is employed to model the stud and wallboard .And beam element is used to model screws which connect the stud and wallboard together. The material parameters of stud and wallboard are gained from the material tests. The effect of both material and geometric non-linear are considered during the process of solving. As a result, the ultimate load and failure mode are gained.Firstly, material tests of both steel stud and wallboard are taken to get the elastic modulus and ultimate strength. Furthermore, since the stud and wallboard are connected by self-drilling screws, the fastening pieces between steel and wallboard tests are taken to get the shear rigidity. Secondly, both hinged end condition could be realized by special clamp and knife edge support. A single studs subject to centric axial loads are tested to get the ultimate load and failure mode. Thirdly, steel frame has different types of bracings, such as steel belt bracing, channel steel bracing and X-shape steel belt bracing. The full-scale tests subject to centric axial loads are carried out for three different types of bracings. The ultimate load and the corresponding failure mode are obtained from tests. Lastly, several factors, such asdifferent wallboard materials, screw spacing, stud distance, web hole have an influence on the ultimate load and failure mode of wall-stud system. In order to estimate them, the full-scale tests of stud braced on one side and both side wallboards subject to centric axial loads are carried out.Based on a series of research, some conclusion can be drawn.(1) Tests have shown satisfactory agreement with finite element result. It shows that the finite element model established by this paper is correct.(2) The tests of steel frame show that the ultimate load of braced stud is 20 percent higher than it of non-bracing stud.(3) The tests of wall-stud system show that the ultimate load of studs braced on both sides wallboard is as twice as it of steel frame. Furthermore, the ultimate load of stud braced on one side wallboard is 25 percent higher than it of steel frame. So the effect of wallboard is obvious.(4) Special clamp and knife edge support can model the hinged end condition well. Chinese cold-formed code is safe enough to design the steel member , subject to centric axial loads , whose thickness is below 2mm.(5) Predictions and observed strengths from the experimental dates are in good agreement. It shows that the effective length factor of stud suggested by this paper is reasonable and feasible.(6) The simplified design formulas based on the Chinese code are derived by this paper. The ultimate load of stud braced by one side or both side wallboards can be gained exactly by these formulas.