| The steel beam may buckle out of the plane of loading before yield,this is called the loss of overall stability.The design of steel beams is often controlled by the lateral buckling of beams.In addition to balanced method,energy method can be used in the solution of lateral buckling of beams.However, in the solving process when energy method was used,diversities existed among different theories,which led directly to the diffenence on the expressions of total potential.The comparison and analysis of different expressions mentioned above suggested that the consideration of transverse stresses is necessary.Based on energy method, the elastic critical moment of simply supported beams was obtained.The checking calculations for the overall stability of steel beams in the current code were based on the analysis of simply supported beams.However,the checking methods for the beams with rigid constraint or semi-rigid constraint at the end was not involved.In view of present situation,the author investigated the lateral buckling of beams with the simultaneous action of end negative moment and transverse loads .Using finite element software ANSYS, 540 specimen beams with 20 kinds of different cross section constants and span lengths were analyzed.The loading condition was the simultaneous action of equal end negative moment and transverse loads on the top flange.The critical moment of the test beams can be calculated from the critical value of loads,which was contained in the results of the eigenvalue buckling analysis by using of ANSYS.Using equivalent critical moment coefficientβb to define the overall stability,The analysis indicated that the influence which the geometry constants of the beams have onβb can be determined by using the parameterξ,and the influence of the negative end moment can be determined by using moment coefficientα.Trough the nonlinear regression analysis of the correlation of the variable parameters above,the approximative formula ofβb was proposed. |
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