Functional Periodicity for Debonding Control of Carbon Fiber-Reinforced Polymer Concrete Interface

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Title: Functional Periodicity for Debonding Control of Carbon Fiber-Reinforced Polymer Concrete Interface

Author(s): Yail J. Kim and Ahmed Ibraheem

Publication: Structural Journal

Volume: 115

Issue: 6

Appears on pages(s): 1791-1801

Keywords: carbon-fiber reinforced polymer (CFRP); debonding; failure; functional periodicity; interface; retrofit; strengthening

Date: 11/1/2018

Abstract:
This paper presents the efficacy of functional periodicity on controlling the occurrence of interfacial failure in concrete members strengthened with carbon fiber-reinforced polymer (CFRP) sheets. The hypothesis tested is that periodically placed stress reducers preserve the integrity of the CFRP-concrete interface by interrupting the progression of mechanical damage, unlike conventional debonding control methods based on a prescribed strain limit. To substantiate this novel debonding-control concept, an experimental program was conducted with three types of stress reducers: epoxy-filled grooves (PG), discrete U-wraps (PU), and silylmodified polymer (SMP) strips (PS). The load-carrying capacity of the PG and PU specimens is enhanced over 60% relative to the capacity of plain-bond control specimens (COT). The periodic configurations of these specimens (the number of grooves and U-wraps) influence the degree of the capacity increase and failure modes by distributing interfacial stresses. Although the capacity of the PS specimens is similar to that of the control, the permanent elastic nature of SMP improves the energy dissipation of the interface, which indicates the potential of the SMP-epoxy hybrid bond for seismic strengthening in tandem with other debonding-control methods. The groove and U-wrap near the loaded end dissipate interfacial fracture energy and impede stress progression. Statistical inference alongside a probability-based assessment corroborates that the individual debonding-control methods and their configurations affect the performance of the CFRP-concrete interface.