Abstract
Determination of fiber-reinforced polymer (FRP) confinement-induced improvements in the mechanical properties of concrete columns under compression is a current concern, particularly if partial confinement applied on a noncircular cross-sectional shape is to be considered. Although several design-oriented predictive formulations have been proposed for the calculation of axial strength and axial strain ductility of FRP-confined concrete, their applications are, in general, limited to a specific cross-sectional shape (circular, square, or rectangular cross section) and a certain confinement arrangement (fully or partially confining system). Accordingly, the aim in this study is to establish new unified strength and ductility models for concrete columns of circular or noncircular cross sections with fully or partially confining FRP systems. To achieve the highest level of predictive performance through a nonlinear regression technique, two datasets, consisting of 2,117 test data of peak strength and 2,050 test data of strain ductility, available in the literature, were collected. The dominance degrees of size effect, sectional noncircularity (corner radius ratio), cross-sectional aspect ratio, and confinement configuration type on confinement effectiveness were evaluated and reflected in the development of these regression-based models. Through predictions of test data compiled in the datasets and a comparison with the performances of available predictive models, the proposed unified formulations demonstrated a high level of reliability and were found to be proper for design purposes.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
This study is a part of the project “Sticker—Innovative technique for the structural strengthening based on using CFRP laminates with multifunctional attributes and applied with advanced cement adhesives” (reference POCI-01-0247-FEDER-039755). The first author also acknowledges support provided by a FCT PhD individual fellowship 2019 (reference SFRH/BD/148002/2019).
Notation
The following symbols are used in this paper:
- A0
- regression coefficient;
- A1
- regression coefficient;
- A2
- regression coefficient;
- A3
- regression coefficient;
- A4
- regression coefficient;
- A5
- regression coefficient;
- B0
- regression coefficient;
- B1
- regression coefficient;
- B2
- regression coefficient;
- B3
- regression coefficient;
- b
- section dimension (shorter side of section);
- Ef
- FRP modulus elasticity;
- fcc
- peak axial strength of FRP-confined concrete;
- fcu
- ultimate axial strength of FRP-confined concrete;
- fc0
- peak axial strength of unconfined concrete;
- fl,u
- confinement pressure at FRP ultimate tensile strain;
- fl,rup
- confinement pressure at FRP rupture;
- h
- longer side of section;
- KL
- FRP confinement stiffness;
- kh
- reduction factor;
- kv
- reduction factor;
- k0
- constant coefficient;
- L
- column height;
- Rca
- cross-sectional aspect ratio, Rca = h/b;
- Rr
- nondimensional parameter, Rr = 2r/b;
- Rsf
- nondimensional parameter, Rsf = sf/b;
- r
- corner radius;
- sf
- distance between FRP strips;
- tf
- nominal thickness of FRP layer;
- wf
- FRP width;
- Y1
- error index;
- Y2
- error index;
- Y3
- error index;
- αSE
- calibration factor for size effect;
- αR
- calibration factor for noncircularity;
- αUF
- unification factor;
- αλ
- calibration factor for sectional aspect ratio effect;
- βSE
- calibration factor for size effect;
- βR
- calibration factor for noncircularity;
- βUF
- unification factor;
- βλ
- calibration factor for sectional aspect ratio effect;
- β0
- calibration factor;
- Δc
- FRP confinement-induced improvements;
- ɛcu
- ultimate axial strain;
- ɛc0
- axial strain corresponding to fc0;
- ɛfu
- ultimate tensile strain of FRP sheet;
- ɛh,rup
- rupture strain of FRP jacket;
- μɛ
- axial strain ductility;
- νu
- ultimate secant Poisson’s ratio;
- ρɛ
- rupture strain ratio of FRP jackets;
- ρK,e1
- FRP confinement stiffness index;
- ξ
- calibration factor;
- ξ0
- calibration factor;
- Ψc
- FRP confinement-induced improvements; and
- ψ
- strain reduction factor.
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Published In
Journal of Composites for Construction
Volume 27 • Issue 6 • December 2023
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© 2023 American Society of Civil Engineers.
History
Received: Mar 31, 2023
Accepted: Aug 2, 2023
Published online: Sep 12, 2023
Published in print: Dec 1, 2023
Discussion open until: Feb 12, 2024
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