This paper presents the outcome of a study of an I-section Glass Fiber Reinforced Polymer (GFRP) beam including retrofitting for damage effects. A total of three beam tests were conducted in the following sequence: GFRP beam with no retrofitting and a single mid-span web brace; the partially damaged (cracked) beam with GFRP plates used for retrofitting; and the retrofitted beam re-tested with the lateral brace at the top flange level. Both cracking and lateral-torsional buckling behavior is studied and experimental load-deflection relationships recorded. Using the mechanical properties of GFRP based on the experimental data, theoretical predictions are made for the buckling load values. The results show that retrofitted damaged beam provided about half of the original strength of the undamaged beam. The study also shows that the mid-span brace played a significant role in beam behavior and strength.