A Study on the effect of adjacent segments of a steel I-Beam with lateral supports on its critical moment

Abstract

One of the most common failure modes in a steel beam structure is lateral torsional buckling (LTB). The unbraced length of the beam is a crucial factor for LTB analysis. The current formula to calculate the critical moment with respect to LTB analysis has not considered the effect of adjacent segments of steel beams with lateral supports. The adjacent segments of beams actually provide restraints to the torsional rotation while maintaining the possibility of warping to occur. This research was intended to observe the effect of the adjacent segments on its critical moment by using the linear buckling analysis and collapse analysis of a finite-element model. The results from the FEM analysis were compared to the value of the critical moment obtained from the available formula in the standard. The linearised buckling analysis results show an increase in the critical moment by 7.02% to 154.83%, while the collapse analysis results show an increase of 2% to 40.41%. As the adjacent segments becomes longer, the increase is less due to the yielding of adjacent beam segments, contributing less stiffness to the beam spanning in between lateral supports.