Creep-induced Distress on the Flexural Behavior of RC Beams Retrofitted with NSM CFRP

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Title: Creep-induced Distress on the Flexural Behavior of RC Beams Retrofitted with NSM CFRP

Author(s): Yail J. Kim and Fuad Khan

Publication: Structural Journal

Volume: 112

Issue: 4

Appears on pages(s): 493-504

Keywords: carbon fiber-reinforced polymer (CFRP); long-term; nearsurface- mounted (NSM); strengthening; sustained load

Date: 7/1/2015

Abstract:
This paper presents the long-term behavior of reinforced concrete (RC) beams strengthened with near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) strips. Various sustained load levels are applied to the strengthened beams and their performance is examined with a focus on residual capacity and failure characteristics. A comparative study with short-term beams is also reported. The NSM CFRP causes wider crack spacing in the strengthened beams relative to an unstrengthened control, implying stress redistribution, and enhances the effective moment of inertia of the beams. The sustained load significantly influences the residual load-carrying capacity of the long-term beams, while its effect is not critical on residual stiffness. The failure mode of the strengthened beams is controlled by the number of NSM CFRP strips and the degree of sustained load. The long-term load accelerates stress concentrations near the CFRP termination, and the accumulated damage propagates along the CFRP-concrete interface. Preliminary design considerations are elaborated and the need for developing long-term design factors is emphasized.