Research On Flexural Capacity Of Four Limbs Built-up Section Cold-formed Steel Box Beam Under Pure Bending

Four limbs built-up Cold-formed steel box beam is a commonly structural memberconsisting of two single C-sections and two single U-sections and connected by self-drillingscrews, but the mechanical performance has not been well studied. This paper mainlydescribes the flexural capacity of four limbs built-up Cold-formed steel box beam under purebending by numerical analysis, and the applied design method is proposed.At first, nonlinear finite element analysis based on ANSYS program involving geometriclarge deformation, materials nonlinear and contact problem is used to simulate the testmodels of Reynaud L. Serrette under eccentric edge load in this paper. In the comparison ofcomputer analysis and experimental results, the accuracy of the finite element model isproved, and provides evidence for the flexural capacity research of four limbs built-upCold-formed steel box beam under pure bending.Then finite element models of four limbs built-up Cold-formed steel box beam underpure bending were set up, and the parametric study was carried out to mainly determine theeffect of height to thickness ratio, width to thickness ratio, width to height ratio, span toheight ratio, material yield strength, the thickness of plates and spacing of screw. The resultsshows, the flexural capacity of four limbs built-up Cold-formed steel box beam under purebending can be dramatically improved by increasing the height to thickness ratio, the materialyield strength and the thickness of plates. The change of width to thickness ratio and width toheight ratio has a greater impact to the flexural capacity within a certain range, and the widthto thickness ratio should not be more than60. However, the span to height ratio and spacingof screw is not a main factor to the flexural capacity, and the spacing of screw between150mm and300mm is proposed. In the common span range, the failure mode of four limbsbuilt-up Cold-formed steel box beam under pure bending is local buckling with overallbending, but the overall bending and twisting instability will not occur.Finally, based on the numerical analysis, the applied design method of four limbsbuilt-up Cold-formed steel box beam under pure bending is proposed, and its feasibility isverified in this paper.