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
DOI:
10.14359/51702417
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.
Related References:
1. Sayin, B., and Manisali, E., “An Investigation of Interfacial Stresses in Reinforced Concrete Beams Using FRP Laminates,” The Journal of Adhesion, V. 86, No. 11, 2010, pp. 1132-1157. doi: 10.1080/00218464.2010.519260
2. Rabinovitch, O., “Bending Behavior of Reinforced Concrete Beams Strengthened with Composite Materials Using Inelastic and Nonlinear Adhesives,” Journal of Structural Engineering, ASCE, V. 131, No. 10, 2005, pp. 1580-1592. doi: 10.1061/(ASCE)0733-9445(2005)131:10(1580)
3. Baky, H. A.; Ebead, U. A.; and Neale, K. W., “Flexural and Interfacial Behavior of FRP-Strengthened Reinforced Concrete Beams,” Journal of Composites for Construction, ASCE, V. 11, No. 6, 2007, pp. 629-639. doi: 10.1061/(ASCE)1090-0268(2007)11:6(629)
4. ACI Committee 440, “Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures (ACI 440.2R-17),” American Concrete Institute, Farmington Hills, MI, 2017.
5. Mostofinejad, D., and Mahmoudabadi, E., “Grooving as Alternative Method of Surface Preparation to Postpone Debonding of FRP Laminates in Concrete Beams,” Journal of Composites for Construction, ASCE, V. 14, No. 6, 2010, pp. 804-811. doi: 10.1061/(ASCE)CC.1943-5614.0000117
6. Kim, Y.; Quinn, K.; Ghannoum, W. M.; and Jirsa, J. O., “Strengthening of Reinforced Concrete T-Beams Using Anchored CFRP Materials,” ACI Structural Journal, V. 111, No. 5, Sept.-Oct. 2014, pp. 1027-1035. doi: 10.14359/51686805
7. Eftkhar, M. R., and Ya’ghubi, M., “Using Boring to Postpone Debonding of CFRP-Composite Concrete Beams,” Journal of Composites for Construction, ASCE, V. 20, No. 1, 2016, p. 04015035. doi: 10.1061/(ASCE)CC.1943-5614.0000595
8. Lee, J., and Lopez, M. M., “Characterization of FRP Uwrap Anchors for Externally Bonded FRP-Reinforced Concrete Elements: An Experimental Study,” Journal of Composites for Construction, ASCE, V. 20, No. 4, 2016, p. 04016012 doi: 10.1061/(ASCE)CC.1943-5614.0000642
9. Wu, Y.-F.; He, L.; and Bank, L. C., “Bond-Test Protocol for Plate-to-Concrete Interface Involving All Mechanisms,” Journal of Composites for Construction, ASCE, V. 20, No. 1, 2016, p. 04015022 doi: 10.1061/(ASCE)CC.1943-5614.0000581
10. Smith, S. T., and Teng, J. G., “Interfacial Stresses in Plated Beams,” Engineering Structures, V. 23, No. 7, 2001, pp. 857-871. doi: 10.1016/S0141-0296(00)00090-0
11. Montgomery, D. C., Design and Analysis of Experiments, eighth edition, Wiley, Hoboken, NJ, 2013.