Fatigue Strengthening of Cracked Steel Beams with Different Configurations and Materials

This paper presents an experimental study on the fatigue behavior of cracked steel beams strengthened using different patch systems and high-strength materials. These materials included normal modulus carbon fiber-reinforced polymer (CFRP) laminate, high-strength steel (HSS) plate, and SafStrip (SAF) plate. Adhesive bonding and mechanical anchorage were selected to attach these overlays. A digital image correlation (DIC) system was adopted to detect stress distribution at the vicinity of the crack front. Different failure modes were observed for specimens with different retrofitting schemes. Test results showed that, in comparison with control specimens without strengthening, application of these retrofitting materials significantly retarded crack propagation and extended fatigue life of defected steel beams. The stiffness decay and crack mouth opening displacement (CMOD) were also reduced in repaired cases. Based on the fatigue cycles when the crack propagated to half-height of the steel beam, CFRP laminate with structural adhesive Araldite 420 led to the best strengthening performance. This study extends the understanding of fatigue repair for steel beams and provides some useful suggestions for the strengthening method. (C) 2016 American Society of Civil Engineers.