The use of Carbon Fibre Reinforced Polymer (CFRP) to strengthen steel structures has attracted the attention of researchers in recent years. The book is extracted from an experimental study about steel sections which strengthened with CFRP plate. I-section steel beams and double lap shear specimens were employed to investigate the bonding behaviour between steel and CFRP. The study focused on the effect of diverse environmental conditions on the mechanical properties of specimens. The book contains beneficial information about strengthening of steel beams, ductility and flexural properties of strengthened beams, and the changes in mechanical properties of steel beams and failure modes. The results of experimental program have been used to find an appropriate analytical procedure to predict the performance of steel/CFRP bonding systems in various conditions. Reading of this book is recommended to all civil engineers who are working in strengthening projects, especially in the field of FRP retrofitting.