Fatigue Rehabilitation of Coped Steel Beams Using Carbon Fibre Reinforced Polymers

Coped beams are susceptible to fatigue cracking in the web at the cope radius when subjected to tension in the coped region. Traditional repair methods such as gouging and re-welding the fatigue crack can cause residual stresses in the heat affected zone where new crack growth can be initiated. Drilling a stop-hole at the crack tip can cause a reduction in net section. Use of an adhesively bonded composite patch over the cracked area can reduce the stress concentration at the crack tip, delaying further crack growth. This research contains the results of a full-scale experimental study on the fatigue mitigation of coped beams using Carbon Fibre Reinforced Polymer (CFRP) patches. Six coped beams were tested. The specimens were pre-cracked to 10 mm prior to repair. Three of the specimens had three layer patches of different configurations of SikaWrap Hex 103C applied to one side. Two specimens had six layer patches; one with all six layers applied to one side, while the other had three layers applied to each side of the web over the crack. The sixth specimen remained unrepaired as a control specimen. This study showed that the single sided repairs provided a marginal increase in fatigue life over the unrepaired beam. The double sided repair was found to increase the fatigue life over three times the fatigue life of the unrepaired specimen. A small-scale experimental study of the effects of varying the pre-crack length prior to specimen repair was also conducted. It was found that the CFRP patch is much more effective at smaller pre-crack lengths. An analytical study of the fatigue mitigation method is also investigated.