Sharif University of Technology Scientia Iranica 1026-3098 17 4 2010 07 01 Lateral-Torsional Buckling of Retrofitted Steel I-Beams Using FRP Sheets 3153 EN M.Z. Kabir Department of Civil Engineering,Amirkabir University of Technology A.E. Seif Department of Civil Engineering,Amirkabir University of Technology Journal Article 2010 09 19 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, stiness 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 eects 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. https://scientiairanica.sharif.edu/article_3153_22346c19e70e93adac9602e52c90b73f.pdf