Lateral Torsional Buckling of Steel I-Beam Retrofitted Using FRP Sheets: Analytical Solution and Optimization

Abstract

This paper presents an analytical investigation on lateral stability of steel metal beam which is retrofitted using FRP patch. The methodology is based on implementing total potential energy and Rayleigh Ritz method. The laminate theory including first order shear deformation is included in this study. The linear elasticity solution is considered for determining of buckling critical load. The compound beam is assumed a simply supported under pure bending. Some combinations of FRP sheets on single or both sides of flanges and web are applied as different cases of section retrofitting in order to investigate the effectiveness of strengthening pattern on the lateral torsional buckling of the metal beam. The FRP sheet can be extended to the total or partial length, full or partial patch, of the beam. In each case, parametric study with variation of fiber orientation is examined to find out the optimum fiber direction for design purposes. The results of this study would be benefitted for retrofitting of existing steel bridges which many of them are exposed to the harsh environment.