Several studies concerning the lateral torsional buckling of horizontally curved I-beams have been made by different researchers. However, these studies are mostly limited to linear analysis and involving only single girders having single span. Nonlinear analysis of horizontally curved I-beams have been very limited or almost none. The aims of this study are to give a brief summary of the studies that have been made involving several factors concerning the lateral torsional buckling capacity of horizontally curved I-beams and to show several analyses that focused on determining the behavior of the horizontally curved I-beams that experience lateral torsional buckling failure. Subjects discussed in this study include: (1) different design provisions involving LTB of curved I-beams; (2) different equations that can be used concerning LTB of curved I-beams; (3) effect of cross frames; (4) effects of cross frame spacing; and (5) analysis results and trends comparing LTB strength of curved I-beams to straight beams. The summary of these studies will be essential in determining the future studies that has to be made involving the lateral torsional buckling of horizontally curved I-girder bridges which should cover single girder and multi girder systems as well as single span and multi span curved bridge systems.

It has been proven in recent studies that for monosymmetric I-section beams, in considering bending moment diagrams caused by any combination of applied end moments and transverse loads acting at the shear centre, the lowest critical lateral torsional buckling moment does not necessarily correspond to uniform bending. This finding is different from the intuitive expectation that researchers have that for lateral torsional buckling of thin walled beams, the lowest critical lateral torsional buckling moment always corresponds to a uniform bending moment diagram. To determine the applicability of the findings stated, considering stepped beams, this study will be focusing on the comparison of the lateral torsional buckling strength trends in monosymmetric I-beams having doubly stepped and compact cross section. Several loading conditions will be applied to see the effect of different moment diagrams having different inflection points on the lateral torsional buckling strength of stepped beams. The study will be made using the finite element program, ABAQUS. The study will investigate stepped beams having monosymmetric ratios ranging from 0.5 to 0.9. These ratios correspond to varying bottom flange width while keeping the top flange width unchanged. Both elastic and inelastic analysis will be carried out for this study. Finally, the findings for this study will be shown using illustrative figures and conclusions will be made.