Lateral-torsional buckling of laterally unsupported single angle sections loaded along geometric axis

• Single angle sections (SAS) members studied for flexural loading along the geometric axis.
• Both material and geometrical nonlinearities with imperfections were incorporated.
• Results validate the upper limit on Cb in AISC-LRFD Specification for SAS members.
• Developed design equations using Perry-Robertson approach of IS 800: 2007.

Equal-leg single angle section (SAS) members were analyzed for flexural loading patterns along the geometric axis. Uniform, triangular, double-curvature and parabolic bending moment were produced using loading patterns over the span of member. Variations in orientation as well as in local and global slenderness ratio were considered to plot normalized moment rotation curves. Both material and geometrical nonlinearities with imperfections in member were also incorporated. These curves were compared with the existing provisions of AISC specification to verify the validity of the upper limit on Cb, which accounts for the effect of loading patterns on the elastic critical buckling moment of SAS members. Design specifications of Indian Standard (IS 800: 2007) for lateral-torsional buckling (LTB) of doubly and mono-symmetric sections were used to develop the design guidelines for limit state of LTB of SAS members. Moment capacity curves from proposed guidelines were compared with the AISC specification and were found to be safe and conservtive.