Debonding of FRP from concrete in strengthening applications: Experimental investigation and theoretical validation.
Item
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Title
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Debonding of FRP from concrete in strengthening applications: Experimental investigation and theoretical validation.
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Identifier
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AAI3187469
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identifier
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3187469
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Creator
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Ali-Ahmad, Mohamad.
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Contributor
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Adviser: Kolluru V. Subramaniam
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Date
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2005
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Civil
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Abstract
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The last few years have witnessed a wider use of fiber reinforced polymer (FRP) sheets for strengthening existing reinforced and prestressed concrete structures. The success of this strengthening method relies on the effectiveness of the stress-transfer between the concrete and the FRP. Although previous studies have demonstrated the merits of using FRP composites, a number of issues are hampering the widespread implementation of this new technology. These issues are related to the shear debonding failure in the FRP-concrete interface. This study consists of the experimental investigation of the interfacial bond behavior between concrete and FRP. A material law for the FRP-concrete interface is established. The instability at failure of the FRP-concrete bond is found to be the result of snapback. The load response of the interfacial bond is shown to change from softening to snap-back upon increasing the bonded length of the FRP composite. The effect of harsh environmental conditions especially freeze-thaw cycles on the interfacial bond is also investigated. The results of the statistical analysis indicate that there is a significant drop in the interfacial fracture energy with freeze-thaw cycling. The results also suggest a progressive decrease in the fracture parameters with freeze-thaw cycling indicating continuous accrual of freeze-thaw damage in the interface. The nonlinear material law of the FRP-concrete interface, which considers the shear-debonding mode of failure, is incorporated into a numerical model for predicting the load-deflection response of FRP-strengthened beams. The load response obtained numerically is compared with existing experimental results. It is shown that the high stress concentration in the FRP-concrete interface close to a flexural crack is responsible for the initiation of debonding. A failure criterion based on a critical value of strain gradient, which can be obtained from a direct shear test, is proposed.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
