Fatigue behaviour of steel elements strengthened with stand CFRP sheets

CFRP sheets are extensively used to strengthen defected steel members through a wet layup process. Different techniques were used to control the quality of bonding, such as vacuum bags and rollers. Recently strand CFRP sheets were applied in the strengthening of steel elements with manufacturer suggested epoxy resin and a primary resin. This study investigated the fatigue behaviour of steel beams and double strap steel joints bonded with strand CFRP sheets. Eight beams were tested under four point bending and eight double strap steel joints were tested under axial tension. Comparisons were made on the failure modes and the fatigue life for specimens bonded with and without the primer epoxy resin. Results showed that the fatigue life of defected steel beams and double strap steel joints bonded with strand CFRP sheets are comparable to that of specimens strengthened with CFRP plates and other high modulus CFRP sheets, whereas a linear reduction in fatigue life was observed when the primer resin was applied on the steel surface of the samples.