The Overall Stability Of Beams Under Loading End Moments With Transverse Load On The Flange

Overall stability is one of the most important factors which influence the carrying capacity of steel beams. However, at present the design method for the overall stability of steel beams is not perfect enough. In the current code for design of steel structures the calculation formula for equivalent critical moment of steel beams under concentrated load, uniform load and end moment are given respectively. This paper researches steel beams under the simultaneous action of end moment and lateral load. The formula above is suitable to these beams, because the axial distribution of moment is non-linear. Trahair proposed a calculation formula for equivalent critical moment of I-beam under the simultaneous action of end moment and lateral load acting on shear center. These formulas above are just suitable for beams under lateral load acting on shear center. However, in engineering practice lateral load mostly acts on the upper flange of the steel beam, which has adverse effect on the overall stability, this research has its certain research significance and application value.In this paper, by using of energy method the calculation formula of equivalent critical moment is derived for constant section I-beams with two symmetrical axes under the simultaneous action of equal end moment and lateral load acting on the upper flange.Using of finite element analysis software ANSYS for model building, the lateral buckling of constant section I-beams with two symmetrical axes of span length 6m, 8m,10m and 12m were simulated respectively, which is under the simultaneous action of equal end moment and lateral load acting on the upper flange. It was found that under the action of equal end moment, critical moment of the beam is somewhat increased because of the appearance of the inflection point, and being different from beams under equal end moment and lateral load acting on shear center, the lateral buckling has great relationship with end moment coefficient a and the parameterξ. The results of finite element analysis were close to theoretical calculation, and error analysis was performed in this paper.According to the results of finite element analysis, a relationship curve of equivalent critical moment coefficientβb and end moment coefficient a is established together with the fitting formula ofβb proposed here.This paper provide reference for further improvement on the calculation formula for equivalent critical moment of steel beams, and provide the production and application with certain reference value.