Role of Fiber Addition in GFRP-Reinforced Slender RC Columns under Eccentric Compression: An Experimental and Analytical Study
Publication: Journal of Composites for Construction
Volume 28, Issue 3
Abstract
Steel reinforcement is widely used in reinforced concrete (RC) constructions. However, the durability of the steel RC elements is often compromised due to corrosion under adverse environmental conditions. Glass fiber‒reinforced polymer (GFRP) bars have become an attractive alternative for replacing steel bars in several RC applications due to their excellent durability properties. However, the GFRP RC columns exhibit lesser stiffness and fail in a brittle manner compared to steel RC columns. Also, the second-order moments and deformations can increase in the GFRP RC columns due to the low elastic modulus of GFRP bars. The pseudoductility and postcracking behavior of GFRP RC columns can be improved by adding discrete fibers. In this study, 12 steel and GFRP RC slender columns are tested under eccentric compression (e/h ratio of 0.5), and the results are presented. The test matrix consists of (1) steel RC columns without fibers; (2) GFRP RC columns without fibers; and (3) GFRP RC columns with four different fiber dosages of (1) 0.50% and 1.0% of macrosynthetic polyolefin (PO); and (2) 0.5% and 1.0% of hybrid (HB) combination of PO and steel fibers. The test results are compared with analytical predictions considering the geometrical and material nonlinearities. The test results show that adding HB fibers resulted in higher strength and pseudoductile failure than columns reinforced with only PO fibers. HB fibers significantly increased flexural rigidity and the ultimate strength of slender GFRP RC columns.
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Data Availability Statement
Test data and analytical code generated during the study are available from the corresponding author upon reasonable request.
Acknowledgments
The authors thankfully acknowledge CSK Technologies, Hyderabad, for their generous support for sponsoring the GFRP bars. Scholarship to the first and second author was provided by the Ministry of Education, India, which is duly acknowledged. Taraka M. R. Balla and Sanket Saharkar share equal first authorship.
Notations
The following symbols are used in this paper:
- Abar
- area of the reinforcement bar;
- Alayer
- area of the concrete layer;
- B
- width of the column;
- e
- eccentricity of the axial load;
- e1
- eccentricity at the top of the column;
- e2
- eccentricity at the bottom of the column;
- Fci
- force in the ith concrete layer;
- cylinder compressive strength of concrete;
- fci
- compressive stress in the concrete at the ith layer;
- fi
- compressive stress in the ith reinforcing bar;
- fy
- yield stress of steel;
- H
- overall depth of the column;
- M
- bending moment;
- n
- number of grid points;
- nl
- number of layers;
- P
- axial compressive load;
- Pi
- force in the ith reinforcing bar;
- Pref
- maximum load at the ascending branch;
- U
- strain energy;
- ti,layers
- thickness of the ith concrete layer;
- Vf
- volume fraction of fibers;
- y
- depth of the layer measured from the extreme compression side;
- yci
- depth of the centroid of the ith layer from the extreme compression side;
- yi
- depth of the centroid of the ith reinforcement bar from the extreme compression side;
- yNA
- depth of neutral axis;
- δc1
- pseudoyield deflection;
- δi
- lateral displacement of the column at the ith grid;
- δi−1
- lateral displacement of the column at the i − 1 grid point;
- δi+1
- lateral displacement of the column at the i + 1 grid point;
- δu
- ultimate deflection;
- Δ
- midheight lateral displacement of the column;
- Δl
- distance between two grids;
- strain in the ith layer of concrete;
- maximum compressive strain in concrete at the extreme layer;
- strain in the ith reinforcing bar;
- λ
- slenderness ratio;
- ϕ
- curvature; and
- ϕi
- curvature at the ith grid point.
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Published In
Journal of Composites for Construction
Volume 28 • Issue 3 • June 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Feb 10, 2023
Accepted: Dec 21, 2023
Published online: Mar 28, 2024
Published in print: Jun 1, 2024
Discussion open until: Aug 28, 2024
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