FRP Tension Ties: State-of-the-Art Review of Existing Design Guidance for Debonding Capacity and Applicability to Concrete Diaphragm Seismic Strengthening
Publication: Journal of Composites for Construction
Volume 26, Issue 2
Abstract
Fiber-reinforced polymer (FRP) ties can be used to provide tensile capacity to seismic-deficient concrete diaphragms, but there are no existing research or design provisions and guidance on how to design such ties is limited. Three commonly used design guidelines, ACI 440.2R, CNR-DT 200, and fib bulletin 90, have various provisions for calculating the axial tension capacity of FRP ties. These provisions have been summarized and their predictive ability compared with two databases, one for unanchored FRP ties and another one for FRP-anchored FRP ties. The unanchored tie data, compiled previously by others, consist of 855 test results from 135 documents; however, the range of parameters is limited, reporting primarily short, thin, and narrow FRP ties that are not representative of real practice. The second database was compiled by the authors and consists of 213 test results from eight papers; although it too is limited to short, thin, and narrow FRP ties anchored with small and shallowly anchored FRP anchors. Nevertheless, the behavior of anchored FRP ties from the database is described and guidance is provided to shape future research, necessary to confirm the suitability of FRP for diaphragm retrofits and develop design guidance.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article. The databases are included as Supplemental Materials, including the following references: (Maeda 1997; Yuan et al. 2001; Yao 2004; Takeo et al. 1997; Zhao et al. 2000; Ueda et al. 1999; Nakaba et al. 2001; Wu et al. 2001; Ren 2003; Zhou 2009; Lu et al. 2005; Bilotta et al. 2011; Ferracuti 2006; Savoia et al. 2009; Pham and Al-Mahaidi 2007; Liu 2012; Taljsten 1994; Faella et al. 2007; Chajes et al. 1996; Woo and Lee 2010; Wu and Jiang 2013; Dai et al. 2002; Sharma et al. 2006; Fen et al. 2008; Adhikari and Mutsuyoshi 2001; Xu et al. 2001; Ueno et al. 2015; Zhang and Smith 2013; Ko et al. 2014; Pellegrino et al. 2008; Kamiharako et al. 2003; Kanakubo et al. 2001; Birmal and Hiroshi 2001; Czaderski and Olia 2012; Hosseini and Mostofinejad 2014; Ormeno et al. 2019; Zhang and Smith 2012a; Ozbakkaloglu et al. 2017; Flores et al. 2019; Zhang et al. 2012; Zhang and Smith 2012b; Smith et al. 2011; Niemitz et al. 2010; Breña and McGuirk 2013).
Notation
The following symbols are used in this paper:
- b
- width of concrete block in shear tests (mm);
- bf
- width of FRP sheet in shear tests (mm);
- danc
- anchor diameter (mm);
- Ef
- modulus of elasticity of FRP materials (MPa);
- FC
- confidence factor;
- fc′
- specified concrete compressive strength (MPa);
- fcm
- mean concrete compressive strength (MPa);
- fctm
- mean concrete tensile strength (MPa);
- ffbk
- IC debonding strength in accordance with fib bulletin 90 (MPa);
- ffdd
- IC debonding strength in accordance with CNR-DT 200 (MPa);
- GFd
- specific fracture energy (MPa);
- hanc
- anchor embedment depth (mm);
- k
- design or predictive multiplier to calculate specific fracture energy;
- kb
- geometry factor to account for ratio of FRP to substrate width;
- kcr
- design or predictive multiplier to calculate IC debonding strength;
- kG
- design or predictive multiplier to calculate specific fracture energy;
- kq
- multiplier to account for loading type;
- k1
- multiplier to normalize by concrete compressive strength;
- k2
- multiplier to account for number of end peeling situations in shear strengthening;
- Le
- active bond length (mm);
- lb
- bonded length (mm);
- ldf
- minimum bond length (mm);
- le
- effective bond length (mm);
- n
- number of FRP sheets or plies;
- P
- applied load;
- ranc
- anchor length (mm);
- s
- offset distance between FRP sheets or plies;
- s0
- slip at point of total debond;
- s1
- slip at point of peak stress;
- tf
- thickness of FRP sheet or ply;
- Vc
- contribution of concrete to shear capacity of element;
- αanc
- fanning angle (degrees);
- γfb
- safety factor, equal to 1.5;
- γf,d
- safety factor, ranging from 1.2 to 1.5;
- δ
- displacement of initial bond line, elongation of FRP sheet;
- ɛfd
- design FRP strain for flexural applications;
- ɛfdd
- IC debonding strain (mm/mm);
- ɛfe
- effective FRP strain for design (mean minus three standard deviations);
- ɛfu
- ultimate FRP strain from testing;
- κν
- multiplier for shear applications; and
- τb1
- peak shear stress.
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Journal of Composites for Construction
Volume 26 • Issue 2 • April 2022
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© 2022 American Society of Civil Engineers.
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Received: Mar 10, 2021
Accepted: Nov 18, 2021
Published online: Feb 14, 2022
Published in print: Apr 1, 2022
Discussion open until: Jul 14, 2022
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