Residual Tensile Strength and Bond Properties of GFRP Bars after Exposure to Elevated Temperatures
Abstract
:1. Introduction
1.1. Background
1.2. Basic Mechanical Properties of GFRP
1.3. Bond of GFRP with Concrete
1.4. GFRP-Reinforced Concrete Members
1.5. Research Significance
2. Materials and Methods
2.1. Tensile Strength Tests
2.2. Bond Pull-out Tests
3. Results
3.1. Tensile Test Results
3.2. Bond Test Results
4. Discussion
4.1. Discussion of Tensile Test Results
4.2. Discussion of Bond Test Results
5. Conclusions
- The residual tensile strength and modulus of vinyl ester GFRP bars generally decreases as the exposure temperature increases. However, the residual strength of the bar that was exposed to 200 °C was larger than the bar exposed 100 °C, which is attributed to the post-cure phenomenon.
- Vinyl ester GFRP bars retain a significant percentage of their tensile strength and elastic modulus after they have cooled from elevated temperatures of up to 400 °C. For example, after exposure to a temperature of 400 °C, the average residual strength of the bar (upon cooling) was 83% of its ambient temperature strength. This contrasts with the percentage of retained properties during exposure to elevated temperature. According to Wang et al. [8], GFRP bars retain about 35% of their ambient temperature strength while subjected to a temperature of 400 °C.
- Generally, the residual pull-out bond strength of the GFRP bars decreased as the exposure temperature increased. There was no significant change in bond stiffness with exposure temperatures of less than 100 °C. The mechanisms of bond transfer also change for different levels of temperature exposure. There is a drastic reduction in bond strength and bond stiffness as prior exposure temperatures reach 400 °C. This is believed to be a major factor affecting post-fire strength assessments of GFRP-reinforced concrete beams, and must be carefully considered in such assessments.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Specimen | No. of Tests | Test Type 1 | Description |
---|---|---|---|
T-A | 3 | TS | Test at ambient temperature. No heat exposure. |
T-100 | 3 | TS | Test at ambient temperature after exposure to temperature of 100 °C at constant load. |
T-200 | 3 | TS | Test at ambient temperature after exposure to temperature of 200 °C at constant load. |
T-400 | 3 | TS | Test at ambient temperature after exposure to temperature of 400 °C at constant load. |
B-A | 3 | PO | Test at ambient temperature. No heat exposure. |
B-100 | 3 | PO | Test at ambient temperature after exposure to temperature of 100 °C. |
B-200 | 3 | PO | Test at ambient temperature after exposure to temperature of 200 °C. |
B-400 | 3 | PO | Test at ambient temperature after exposure to temperature of 400 °C. |
Specimen | Temperature Exposure, °C | Mean Failure Load, kN | COV (%) of Strength | Mean Residual Tensile Strength, MPa | Mean Residual Modulus of Elasticity, MPa | COV (%) of Modulus of Elasticity | Ratio of Residual Strength to Ambient Temperature Strength | Ratio of Residual Modulus to Ambient Temperature Modulus |
---|---|---|---|---|---|---|---|---|
T-A | 22 | 191.7 | 4.1 | 648.9 | 39603 | 3.9 | 1 | 1 |
T-100 | 100 | 167.3 | 1.3 | 566.1 | 38969 | 2.2 | 0.87 | 0.98 |
T-200 | 200 | 187.3 | 4.2 | 633.8 | 38388 | 5.2 | 0.98 | 0.97 |
T-400 | 400 | 158.3 | 1.4 | 535.7 | 32839 | 3.1 | 0.83 | 0.83 |
Specimen Name | Temperature at Embedded Portion of Bar, °C | Mean Failure Load, KN | COV (%) of Failure Load | Mean Residual Bond Strength, MPa | Ratio of Residual Bond Strength to Ambient Temperature Bond Strength |
---|---|---|---|---|---|
B-A | 22 | 64.2 | 7.9 | 11.3 | 1.00 |
B-100 | 100 | 61.9 | 13.3 | 10.9 | 0.96 |
B-200 | 200 | 48.6 | 4.6 | 8.5 | 0.76 |
B-400 | 400 | 17.6 | 64.7 | 3.1 | 0.27 |
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Ellis, D.S.; Tabatabai, H.; Nabizadeh, A. Residual Tensile Strength and Bond Properties of GFRP Bars after Exposure to Elevated Temperatures. Materials 2018, 11, 346. https://doi.org/10.3390/ma11030346
Ellis DS, Tabatabai H, Nabizadeh A. Residual Tensile Strength and Bond Properties of GFRP Bars after Exposure to Elevated Temperatures. Materials. 2018; 11(3):346. https://doi.org/10.3390/ma11030346
Chicago/Turabian StyleEllis, Devon S., Habib Tabatabai, and Azam Nabizadeh. 2018. "Residual Tensile Strength and Bond Properties of GFRP Bars after Exposure to Elevated Temperatures" Materials 11, no. 3: 346. https://doi.org/10.3390/ma11030346