Uniaxial Compression Behavior of Short Square and Circular RC Piles Constructed with GFRP Bars and Spirals Preconditioned in Simulated Marine Environments
Publication: Journal of Composites for Construction
Volume 26, Issue 3
Abstract
The current experimental investigation assessed the durability of reinforced concrete (RC) piles with glass fiber-reinforced polymer (GFRP) bars and spirals exposed to simulated marine environments. A total of 18 specimens—9 square (300 mm in cross section) and 9 circular (304 mm in diameter)—and short RC piles were prepared and tested under uniaxial compression. For each pile geometry, three specimens were reinforced with pristine GFRP bars as reference piles. The other six piles were reinforced with GFRP bars that had been exposed to marine environments at subtropical regions (22°C) or accelerated aging temperature (60°C) for 12 months, three specimens for each environment. Mechanical property and microstructural analysis tests were carried out to characterize the conditioned/aged GFRP bars. The GFRP-RC piles conditioned at 60°C exhibited similar behavior to their reference counterparts. The current environmental reduction factors for GFRP reinforcing bars stipulated in design codes and guidelines are conservative. A more accurate design equation to calculate the axial capacity of piles should consider the contribution of longitudinal GFRP bars even when exposed to marine environments.
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Acknowledgments
The authors express their gratitude and sincere appreciation to the Natural Science and Engineering Research Council of Canada (NSERC), the NSERC Research Chair in Innovative FRP Reinforcement for Concrete Structures, the Tier-1 Canada Research Chair in Advanced Composite Materials for Civil structures, the Fonds Québécois de la Recherche sur la Nature et les Technologies (FQRNT), the Canadian Foundation for Innovation (FCI), and the significant efforts of the technical staff of the CFI structural laboratory in the Department of Civil Engineering at the University of Sherbrooke. The authors are very grateful to Pultrall Inc. (Thetford Mines, Quebec, Canada), who donated FRP materials to support this investigation. The third author also acknowledges the Advance Queensland Industry Research Fellowship Program (AQIRF 119-2019RD2) for financial support.
Notation
The following symbols are used in this paper:
- Af
- total area of longitudinal GFRP bars;
- Afrp
- nominal cross-sectional area of the longitudinal bar;
- Ag
- gross sectional area of a concrete pile;
- CE
- environmental reduction factor specified in AASHTO (2018a);
- db
- nominal bar diameter;
- ds
- cross-section diameter of ties, hoops, and spirals;
- Ef
- tensile modulus of elasticity of GFRP bars;
- Efc
- compressive modulus of elasticity of the GFRP bars taken as equal to the tensile modulus of elasticity of bars;
- Fb-eu-mod.
- theoretical buckling stresses;
- concrete cylinder strength at 28 days;
- kl/r
- slenderness ratio of GFRP bars;
- l
- unbraced bar length (spiral pitch);
- ld
- bonded length;
- P
- tensile load of the bond test;
- Pb
- theoretical load carried by GFRP bars;
- Pbar
- experimental load carried by longitudinal bars;
- Pexp
- ultimate compression load;
- Pexp2
- second peak load;
- Pr-AASHTO
- factored axial-load resistance of FRP-RC piles specified in AASHTO (2018a);
- Pr-AASHTO-Modified
- factored axial-load resistance of GFRP-RC piles calculated with the AASHTO (2018a) modified equation;
- Pr-S6
- factored axial-load resistance of FRP-RC columns specified in CSA (2019a);
- Ps
- shear failure load;
- r
- radius of gyration for the nominal cross section of the longitudinal bars;
- rs
- bent portion radius of square spirals or ties;
- S
- spacing between transverse reinforcement (unbraced bar length);
- SH
- average horizontal shear strength;
- α1
- ratio of average stress in rectangular compression block;
- ɛa
- overall axial strain;
- ɛr
- lateral strain;
- ɛv
- volumetric strain of concrete core;
- ν
- Poisson’s ratio of plain concrete;
- ρl
- longitudinal reinforcement ratio;
- ρv
- transverse reinforcement ratio;
- τ
- average bond strength;
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Journal of Composites for Construction
Volume 26 • Issue 3 • June 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Aug 24, 2021
Accepted: Feb 3, 2022
Published online: Apr 15, 2022
Published in print: Jun 1, 2022
Discussion open until: Sep 15, 2022
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