The Over-All Stability Analysis Of Gable Portal Frame Considering The Arch Effect Subjected To Uniform Loading

Steel structure of light-weight buildings with gabled frames is a widely used steel structural style in China at present. This paper starts with the deficiency of the Specificaion in calculating the effective length factors of gable portal frames. When the gable portal frame subjected to the vertical uniform loading, it conducts the arch effect—1.Rafter axial force is large when the slope of rafter is big. 2. Having the span change effect. 3. Low height-span gable portal frame occur snap through buckling. Global stability method is used to analysis the stability of gable portal frames.The linear elastic slope deflection equations of gable portal frames when occur the side-sway and non-sway buckling are derived. The equations considere the rafter slope and the vertical uniform loading subjected on the rafter. The Established equations of non-sway buckling can consider the effect of snap change effect of gable frame. Based on the equations, some portal frame model are calculated, also got the effective length factors of frames and comparared these factors with the Code.The ANSYS finite element program is used to analysis the over-all stability of portal frames, with considering axial force, moment, and geometrical nonlinear effect. The the accurate effective length factors of gable portal frames are got. The paper also found the unbraced low height-span ratio gable portal frames can produce the non-sway buckling, and the reason of non-sway buckling are given. Through over-all stability analysis, the influence of height-span ratio, rafter slope to the stability and the effective factors of gable portal frames are also presented in this paper.The snap through buckling of gable portal frames are studied. And related factors concerned with snap through buckling of portal frames are presented and studied. And the character of snap through buckling of gable portal frames is got.Through work of this paper, we have a deeper understanding of stability of gable portal frames, and give some suggestion in design and calculating portal frames.