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


Department of Civil Engineering,Amirkabir University of Technology


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.