Lateral-Torsional Buckling of Retrofitted Steel I-Beams Using FRP Sheets

This study intends to present an analytical solution of lateral-torsional buckling of an Ibeam, which is retrofitted using FRP sheets. The analytical solution is based on calculating the total potential energy and applying the Rayleigh-Ritz method. It is supposed that the FRP sheet can be used on anges. Therefore, two cases of retro tting are the I-beam with Top-Bottom retrofitted anges (TB) and Bottom retrofitted ange Only (BO). It is also assumed that the ange and the FRP sheet are considered as a continuous hybrid element and the Classical Lamination Theory (CLT) can be applied. Subsequently, from the energy method, sti ness parameters of retro tted sections are produced for both cases of TB and BO and the critical moment is presented for the retro tted I-beam under positive end moments. Finally, numerical consideration and a parametric study with various fiber angles in a [+=􀀀] laminate sequence are used for both simple and clamped beams under some typical loadings, to inspect the e ects of FRP sheets on the development of the lateral-torsional buckling capacity. Moreover, FEM results are produced from numerical models made up of 2D shell elements to verify the analytical solution.