Axial Behavior of Concrete Prisms Confined by FRP Laminate and Spike Anchors
Publication: Journal of Composites for Construction
Volume 26, Issue 1
Abstract
Reinforced concrete (RC) buildings constructed before introducing ductile design requirements may exhibit undesirable seismic behavior. One such vulnerability is the lack of confinement to end regions that may lead to nonductile compression failures for RC walls. To overcome this vulnerability, strengthening nonductile RC walls is often required. The addition of confinement to end region concrete can be implemented using carbon fiber-reinforced polymer (FRP) laminate and spike anchors. The main issue encountered when applying this strengthening method is the lack of existing design guidance on this confinement method, due to a lack of experimental data to validate the approach. The objective of this study was to provide the necessary experimental data to quantify the behavior of concrete confined with FRP laminate and spike anchors. Static monotonic axial compression tests were conducted on 46 concrete prisms confined with FRP laminate and spike anchors and the other six unconfined concrete prisms. These prisms represented the end regions of RC walls. The variables investigated for the confined test prisms included anchor spacing, anchor cross-sectional area, and cross-sectional aspect ratio. It shows that peak strength increased significantly with the decrease of anchor spacing and the increase of anchor cross-sectional area. An increase in anchor cross-sectional area had a more considerable influence on the failure strain than a decrease in anchor spacing. The cross-sectional aspect ratio of the prisms had an insignificant impact on failure strain. When gross anchor cross-sectional area was constant in the confinement arrangement, larger peak strength, strain at peak, and failure strain were generally observed in prisms confined with smaller and more closely spaced anchors. Design recommendations were given on the test variables based on test results.
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Acknowledgments
Research funding was supported by the Earthquake Commission (EQC), Mapei New Zealand, and the University of Auckland. The authors thank Allied Concrete NZ for providing the ready-mix concrete and Mapei New Zealand and Sika New Zealand for providing the FRP products and epoxy resin products. The generous technical support from BBR Contech in the installation of the FRP materials is appreciated. Lastly, the authors acknowledge the contributions of Mark Byrami and Nimra Umair, the lab technicians at the University of Auckland.
Notation
The following symbols are used in this paper:
- Ad
- cross-sectional area of dry anchor products in mm2;
- b
- prism width in mm;
- Ec
- modulus of elasticity of concrete cylinders in GPa;
- fc′
- compressive strength of concrete cylinders in MPa;
- fccu (fccu,ave)
- stress at failure (average stress at failure) of confined prisms in MPa;
- fco (fco,ave)
- peak strength (average peak strength) of unconfined prisms in MPa;
- fcp (fcp,ave)
- peak strength (average peak strength) of confined prisms in MPa;
- fcu (fcu,ave)
- stress at failure (average stress at failure) of unconfined prisms in MPa;
- fft
- flexural tensile strength of concrete beams in MPa;
- ft
- split tensile strength of concrete cylinders in MPa;
- H
- prism height in mm;
- Lf
- fan length in mm;
- l
- prism length in mm;
- Sd
- anchor spacing in mm;
- Wf
- fan width in mm;
- ɛc′
- strain at peak of concrete cylinders in 10−3;
- ɛccr (ɛccr,ave)
- cracking strain (average cracking strain) of confined prisms in 10−3;
- ɛccu (ɛccu,ave)
- failure strain (average failure strain) of confined prisms in 10−3;
- ɛco (ɛco,ave)
- strain at the peak (average strain at the peak) of unconfined prisms in 10−3;
- ɛcp (ɛcp,ave)
- strain at the peak (average strain at the peak) of confined prisms in 10−3;
- ɛcr (ɛcr,ave)
- cracking strain (average cracking strain) of unconfined prisms in 10−3;
- ɛcu (ɛcu,ave)
- failure strain (average failure strain) of unconfined prisms in 10−3;
- ɛdowel
- maximum observed lateral strain of FRP anchor dowels in 10−3;
- ɛfan
- maximum observed lateral strain of FRP anchor fans in 10−3; and
- ρc
- density of tested concrete cylinders in kg/m3.
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Published In
Journal of Composites for Construction
Volume 26 • Issue 1 • February 2022
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Feb 5, 2021
Accepted: Sep 1, 2021
Published online: Nov 9, 2021
Published in print: Feb 1, 2022
Discussion open until: Apr 9, 2022
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