1 Introduction
Type | Tensile strength (MPa) | Rupture strain | Elastic modulus (GPa) | Density (g/mm3) | Remarks |
---|---|---|---|---|---|
Carbon fiber | 1970 | 0.012 | 169.0 | 0.0018 | |
Aramid fiber | 2209 | 0.028 | 80.1 | 0.0014 | |
Glass fiber | 792 | 0.018 | 45.0 | 0.0025 | |
Basalt fiber | 1226 | 0.019 | 68.4 | 0.0027 | |
PEN fiber | 842 | 0.090 | 17.5 | 0.0014 | Nonlinear σ–ε relationship |
PET fiber | 613 | 0.150 | 7.1 | 0.0014 | Nonlinear σ–ε relationship |
2 Research Background and Objectives
- Expand test data on confinement effect of low to normal strength concrete by LRS PEN FRP as well as by BFRP;
- Compare and identify the differences, if any, in the behavior of the concretes confined by LRS PEN FRP and more conventional BFRP including stress–strain relationship, failure mode, and effectiveness of fibers;
- Investigate the overlap length of LRS PEN FRP; and
- Suggest a simplified modeling method of FRP-confined concrete.
3 Material Properties and Test Preparation
3.1 Fibers and Adhesive
Type | Density (g/mm3) | Width (mm) | Thickness (mm) | Cross-sectional area (mm2) | Shape of cross-section |
---|---|---|---|---|---|
Basalt fiber roving | 0.0027 | 4.00 | 0.113 | 0.45 | Rectangular |
PEN fiber roving | 0.0014 | 2.37 | 0.840 | 2.00 | Circular |
Type | Strength (MPa) | Rupture strain (%) | E1 (GPa) | E2 (GPa) | ||
---|---|---|---|---|---|---|
Mean | Standard deviation | Mean | Standard deviation | |||
BF roving | 1226 | 62.7 | 1.95 | 0.17 | 68.4 | – |
PEN fiber roving | 822 | 18.1 | 8.03 | 0.51 | 17.4 | 8.30 |
PEN fiber sheet | 842 | 25.9 | 9.01 | 0.71 | 17.5 | 8.33 |
PEN FRP | 912 | 27.1 | 9.13 | 0.63 | 21.4 | 8.59 |
Adhesive | 41 | 1.7 | 2.58 | 0.25 | 1.6 | – |
3.2 Preparation for Confinement Test
3.2.1 Concrete Cylinders Used for Main Confinement Test and Additional Confinement Test
Test program | Type | No. of cylinders | No. of FRP layers |
---|---|---|---|
Main confinement test | Control | 3 | – |
BFRP wrap | 9 | 2, 4, 6 | |
PEN FRP wrap | 9 | 1, 2, 3 | |
Additional confinement test | Control PEN FRP wrap | 1 3 | – 2 |
3.2.2 Fiber Wrapping
Fiber type | No. FRP layers | Cylinder diameter (mm) | Ef (GPa) | Tf (mm) | El (MPa) | Fiber vol. ratio (%) |
---|---|---|---|---|---|---|
BF | 2 | 150 | 68.4 | 0.226 | 206 | 0.60 |
4 | 0.452 | 412 | 1.21 | |||
6 | 0.678 | 618 | 1.81 | |||
PEN FRP | 1 | 21.4 | 0.840 | 239 | 2.25 | |
2 | 1.680 | 479 | 4.50 | |||
3 | 2.520 | 719 | 6.74 |
3.2.3 Procedure of Confinement Test
4 Confinement Test Results
4.1 Results of Main Confinement Test
4.1.1 Stress–Strain Behavior of Confined Concrete
Index | \(f'_{co}\) (MPa) | \(f'_{cc}\) (MPa) | εco (m/m) | εccu (m/m) | fcc @ εco (MPa) | εh @ εco (m/m) | εh,rup (m/m) | \(f_{l}\) (MPa) | \(f_{l}\) / \(f'_{co}\) | Failure mode |
---|---|---|---|---|---|---|---|---|---|---|
C-C-1 | 25.0 | 0.0024 | ||||||||
C-C-2 | 24.6 | 0.0019 | ||||||||
C-C-3 | 24.8 | 0.0020 | ||||||||
C-B2-1 | 37.0 | 0.021 | 25.6 | 0.0014 | 0.019 | 3.99 | 0.16 | RP | ||
C-B2-2 | 35.4 | 0.021 | 26.3 | 0.0010 | 0.021 | 4.39 | 0.18 | RP | ||
C-B2-3 | 33.2 | 0.020 | 23.2 | n/a | 0.023 | 4.79 | 0.19 | RP | ||
C-B4-1 | 47.9 | 0.027 | 25.5 | 0.0009 | 0.022 | 9.16 | 0.37 | RP | ||
C-B4-2 | 50.2 | 0.025 | 29.8 | 0.0006 | 0.019 | 7.64 | 0.31 | RP | ||
C-B4-3 | 48.9 | 0.025 | 29.6 | 0.0009 | 0.018 | 7.40 | 0.30 | RP | ||
C-B6-1 | 62.0 | 0.034 | 26.8 | 0.0011 | 0.020 | 12.59 | 0.50 | RP | ||
C-B6-2 | 62.7 | 0.031 | 28.9 | 0.0008 | 0.022 | 13.80 | 0.55 | RP | ||
C-B6-3 | 62.9 | 0.031 | 28.0 | 0.0010 | 0.019 | 12.04 | 0.48 | RP | ||
C-P1-1 | 33.9 | 0.033 | 20.7 | 0.0011 | 0.032 | 4.51 | 0.18 | DB | ||
C-P1-2 | 33.9 | 0.034 | 22.8 | 0.0013 | 0.031 | 4.41 | 0.18 | DB | ||
C-P1-3 | 33.9 | 0.033 | 23.6 | 0.0009 | 0.038 | 5.09 | 0.20 | DB | ||
C-P2-1 | 42.0 | 0.035 | 26.6 | 0.0006 | 0.034 | 9.32 | 0.37 | DB | ||
C-P2-2 | 40.7 | 0.037 | 24.8 | 0.0012 | 0.040 | 10.62 | 0.42 | D-R | ||
C-P2-3 | 41.6 | 0.039 | 27.7 | 0.0005 | 0.046 | 11.75 | 0.47 | D-R | ||
C-P3-1 | 62.6 | 0.061 | 26.7 | 0.0008 | 0.067 | 23.51 | 0.94 | DB | ||
C-P3-2 | 62.6 | 0.052 | 27.3 | 0.0009 | 0.043 | 16.67 | 0.67 | DB | ||
C-P3-3 | 62.6 | 0.054 | 27.9 | 0.0008 | 0.050 | 18.85 | 0.75 | DB |
4.1.2 Strength Enhancement
4.1.3 Strain Enhancement and Ultimate Poisson’s Ratio
4.2 Simplified Modeling for Stress–Strain Relationship
4.3 Results of Additional Confinement Test
Index | f’co (MPa) | εco (m/m) | \(f'_{cc}\) (MPa) | εccu (m/m) | εh,rup (m/m) | \(f_{l}\) (MPa) | \(f_{l}\) / \(f'_{co}\) | Failure mode |
---|---|---|---|---|---|---|---|---|
Control | 35.0 | 0.002 | ||||||
C-P2-0 mm | 52.5 | 0.033 | 0.037 | 9.96 | 0.31 | RP | ||
C-P2-50 mm C-P2-150 mm | 52.7 60.3 | 0.042 0.037 | 0.040 0.039 | 10.64 10.43 | 0.33 0.32 | D-R RP |
5 Discussion on Confinement Test Results and Validation of Suggested Model
5.1 f′co and fcc at εco
5.2 Failure Mode and Overlap Length
5.3 Hoop Rupture Strain and FRP Efficiency Factor
5.4 Validation of Suggested Model in View of Merged Test Data
Index | f′co (MPa) | tf (mm) | E1, E2 (GPa) | f′cc (MPa) | εccu (m/m) | εh,rup (m/m) | Index | f′co (MPa) | tf (mm) | E1, E2 (GPa) | f′cc (MPa) | εccu (m/m) | εh,rup (m/m) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Control | 39.2 | Control | 39.2 | ||||||||||
AT-1-1 | 0.169 | 115.2, n/a | 61.4 | 0.0233 | 0.0316 | PET900-1-1 | 1.262 | 18.9, 7.4 | 46.9 | 0.0599 | 0.0502 | ||
AT-1-2 | 0.169 | 115.2, n/a | 62.7 | 0.0233 | 0.0313 | PET900-1-2 | 1.262 | 18.9, 7.4 | 533 | 0.0541 | 0.0526 | ||
AT-1-3 | 0.169 | 115.2, n/a | 55.8 | 0.0207 | 0.0321 | PET900-1-3 | 1.262 | 18.9, 7.4 | 43.7 | 0.0329 | 0.0475 | ||
Control | 39.2 | Control | 39.2 | ||||||||||
AT-2-1 | 0.338 | 115.2, n/a | 90.1 | 0.0380 | 0.0289 | PET900-2-1 | 2.524 | 18.9, 7.4 | 77.5 | 0.0530 | 0.0505 | ||
AT-2-2 | 0.338 | 115.2, n/a | 88.3 | 0.0345 | 0.0305 | PET900-2-2 | 2.524 | 18.9, 7.4 | 69.5 | 0.0582 | 0.0510 | ||
AT-2-3 | 0.338 | 115.2, n/a | 83.3 | 0.0368 | 0.0296 | PET900-2-3 | 2.524 | 18.9, 7.4 | 67.2 | 0.0692 | 0.0520 | ||
Control | 39.2 | Control | 39.2 | ||||||||||
AT-3-1 | 0.507 | 115.2, n/a | 113 | 0.0439 | 0.0274 | PET900-3-1 | 3.786 | 18.9, 7.4 | 97.8 | 0.0966 | 0.0409 | ||
AT-3-2 | 0.507 | 115.2, n/a | 116 | 0.0460 | 0.0246 | PET900-3-2 | 3.786 | 18.9, 7.4 | 97.2 | 0.0796 | 0.0460 | ||
AT-3-3 | 0.507 | 115.2, n/a | 118 | 0.0478 | 0.0297 | PET900-3-3 | 3.786 | 18.9, 7.4 | 107.1 | 0.0743 | 0.0483 | ||
Control | 39.2 | Control | 32.5 | ||||||||||
PEN-1-1 | 0.848 | 27.0, 12.0 | 54.9 | 0.0364 | 0.0423 | PET600-1-1 | 0.841 | 18.9, 7.4 | 41.6 | 0.0510 | 0.0817 | ||
PEN-1-2 | 0.848 | 27.0, 12.0 | 52.6 | 0.0370 | 0.0501 | PET600-1-2 | 0.841 | 18.9, 7.4 | 41.7 | 0.0492 | 0.0797 | ||
PEN-1-3 | 0.848 | 27.0, 12.0 | 50.4 | 0.0371 | 0.0439 | PET600-1-3 | 0.841 | 18.9, 7.4 | 42.2 | 0.0430 | 0.0676 | ||
Control | 39.2 | Control | 32.5 | ||||||||||
PEN-2-1 | 1.696 | 27.0, 12.0 | 78.7 | 0.0410 | 0.0521 | PET600-2-1 | 1.682 | 18.9, 7.4 | 64.5 | 0.0661 | 0.0722 | ||
PEN-2-2 | 1.696 | 27.0, 12.0 | 77.6 | 0.0424 | 0.0430 | PET600-2-2 | 1.682 | 18.9, 7.4 | 65.8 | 0.0724 | 0.0786 | ||
PEN-2-3 | 1.696 | 27.0, 12.0 | 77.1 | 0.0427 | 0.0362 | PET600-2-3 | 1.682 | 18.9, 7.4 | 67.4 | 0.0753 | 0.0784 | ||
Control | 39.2 | Control | 32.5 | ||||||||||
PEN-3-1 | 2.544 | 27.0, 12.0 | 105 | 0.0580 | 0.0468 | PET600-3-1 | 2.523 | 18.9, 7.4 | 77.4 | 0.0646 | 0.0640 | ||
PEN-3-2 | 2.544 | 27.0, 12.0 | 102 | 0.0496 | 0.0416 | PET600-3-2 | 2.523 | 18.9, 7.4 | 85.0 | 0.0732 | 0.0666 | ||
PEN-3-3 | 2.544 | 27.0, 12.0 | 101 | 0.0541 | 0.0454 | PET600-3-3 | 2.523 | 18.9, 7.4 | 86.5 | 0.0740 | 0.0480 | ||
Control | 24.1 | ||||||||||||
CL-1 (PET) | 0.841 | 19.7, 7.55 | 37.5 | 0.0560 | 0.0561 | ||||||||
CL-2 (PET) | 1.682 | 19.7, 7.55 | 63.7 | 0.0923 | 0.0821 | ||||||||
CL-3 (PET) | 2.523 | 19.7, 7.55 | 88.5 | 0.1104 | 0.1030 |