Strengthening of tensile steel members and bolted joints using adhesively bonded CFRP plates

The use of CFRP composites in the rehabilitation of structurally inadequate buildings and bridges is rapidly increasing but the majority of the applications covers reinforced concrete structures. The recent improvements both of the mechanical properties of the carbon fibers and the bonding techniques, provide the possibility of applying the same technologies for the strengthening and repairing of metallic structures. This paper presents an experimental and numerical study to verify the effectiveness of the use of CFRP pultruded plates to reinforce steel elements commonly used in structural steelworks. Both common applications of CFRP plates, such as double reinforcements of continuous steel plates and double lap joints, and so far less diffused solutions such as bolted joints, were considered. The specimens were prepared using CFRP plates and adhesives currently used in civil engineering applications. The experiments were extensively instrumented along the whole bond length of the CFRP lamina by means of several strain-gauges. The force transfer mechanism and the failure mechanism were evaluated from both analytical and numerical models. In particular, suitable finite element models were implemented for those cases where no analytical solutions were available.