On the evaluation of lateral-torsional buckling of web-tapered cantilevers with doubly symmetric I-section

Recently, structural engineers have tended to design stronger and lighter structures due to economic reasons, technical developments in computer-aided design, and improvements in manufacturing. The demand for designing stronger and lighter structures has led to the compulsory considering structural efficiency and stability loss at the design level. Lateral-torsional buckling (LTB) is a major stability loss for web-tapered cantilevers with doubly symmetric I-section, which are aesthetic and structurally efficient. The elastic LTB loads of these cantilevers should be calculated at the design level since the LTB may happen before bending stress reaches yield. Studies related to the LTB of cantilevers are rare and require numerical solutions since the LTB mode shape of cantilevers is complex compared to simply supported beams. The present study introduces an analytical procedure based on the energy method for calculating elastic LTB of web-tapered cantilevers with doubly-symmetric I-section in two different forms. The analytical model considers different transverse load types, positions of loads, and web tapering degrees. The analytical solutions were validated with one-dimensional finite element analysis using a beam element. Excellent accordance between results was demonstrated. The general LTB behavior of web-tapered cantilevers with doubly symmetric I-section was clarified with detailed comments based on results obtained from the presented analytical model.