Abstract:

In steel structures, beams are usually assembled so as to be under bending about their major axis in order to use the structural material economically. Two major problems take place in design of these steel beams. First problem is exceeding of yield stress at the extreme fiber of the section. External force magnitude for any loading case which causes exceeding of yield stress on a steel beam can be easily calculated. Second problem is loss of stability. In beams which are loaded so as to be under bending about their major axis an equilibrium state is also possible for a certain load magnitude, in which the beam is twisted and buckled about its weak axis. This case is called lateral torsional buckling. Depending on the loading case, yield stress of the structural material and slenderness of the beam, which is related to section properties and length of the element, lateral torsional buckling may occur before the extreme fiber of the section reaches to yield stress. In this case, instead of first yield moment, lateral torsional buckling moment should be considered in design of the beam. In this paper, application of finite differences method for determining elastic critical lateral torsional buckling moment of cantilever I sections which are loaded from shear center is presented. The results are compared with ABAQUS software and it is seen that results obtained from the presented 1D model and ABAQUS software coincide.

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