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Title: Composite patch repair of fatigue-damaged steel members
Author: Aggelopoulos, Eleftherios S.
ISNI:       0000 0001 3399 3211
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2007
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The use of adhesively bonded composite reinforcements for strengthening metallic structures is a relatively new technique that has been introduced in the past few years. The technique was first applied for crack patching of aircraft components, with the first civil engineering applications on steel bridge members, which have been damaged due to corrosion or fatigue, being more recent. The finite element (FE) method was employed in order to analyse a steel plate containing a crack and reinforced with an adhesively bonded composite patch. The role of parameters such as the crack size and the properties (modulus and thickness) of the patch and the adhesive was examined. Results in tenns of the stress magnification factor at the crack tip and the shear and peel stress distributions at the steel/adhesive interface were obtained. Following this, the FE results were used in order to develop an analytical model for estimating the stress magnification factor (YJ for patched cracks. The effects of patch pre-stressing and thennal loading due to mismatch in thennal expansion coefficients of the materials involved were also examined. Patch debonding was also investigated. Two different cases were considered, namely a patched plate without a crack and a patched plate containing a crack. For the latter, apart from debonding being initiated from the patch extremities (patch end debonding), crack mouth debonding was also considered. The effect of debonding on Yp was determined. Following this, debonding was modelled as a crack located at the steel/adhesive interface and a fracture parameter, namely the energy release rate G, was obtained at the interface crack tip. An analytical model for G pertaining to patch end debonding was also developed. An experimental study was carried out in order to validate the model proposed for Yp' Fatigue tests of patched cracked specimens were performed and crack growth data was obtained and compared with predictions using the analytical model for Yp inside the well known Paris crack growth law. Prior to this, the tensile properties for steel and composite and the fatigue properties of steel were determined from tests. The results indicate that the models obtained can be used for the design of composite patch repairs of steel members. Therefore, they were included in a design methodology, which is also presented. The latter could form the basis of a more ,comprehensive future design guide, or even complete existing guides, such as the CIRIA . guide (Cadei et a1. 2004).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available