Experimental Evaluation of PSC Structures from FRP with a Prestressing Strengthening Method
Abstract
:1. Introduction
2. Experimental Materials and Structural Test Details
2.1. Mixture Properties
2.2. Test Specimen Design and Fabrication
2.3. Test Method
3. Experimental Evaluation Results
3.1. Load–Displacement Tests
3.2. Load–Displacement Test Outcomes
3.3. Concrete Strain Measurements
3.4. Steel Strain Measurements
4. Conclusions
- (1)
- When comparing the design and the experimental values, the crack load showed a large difference in the NSM (no prestressing) method, but in terms of yield load, all experimental values were higher than the design values. In addition, the EP method values were 1.5 to 2 times higher than the NSM (prestressing or no prestressing) method for each load.
- (2)
- Both the EP and NSM (prestressing) methods applied to high-strength (40 MPa) and low-strength (20 MPa) concrete showed 5% to 60% higher stiffness than that of the control specimen. As the internal prestress force increased, the stiffness increased. Owing to the additional prestressing of the reinforced material according to the strengthening method, the specimens of EP and NSM methods showed higher stiffness than the control specimen, but a brittle behavior was observed for these specimens.
- (3)
- When the load–displacement curves of all specimens were compared, the stiffness up to the yield load increased almost two times compared with that of the control specimen in the cases of PH4EP and PL4EP, but in the case of specimens tested with the NSM method (no prestressing), there was no increase in stiffness and the overall trend was similar to that of the control specimen (strengthening effect: EP > NSM (prestressing) > NSM (no prestressing).
- (4)
- The strain of the reinforced bar was 0.002 or higher, and both the NSM (prestressing) and EP methods showed a higher yield strength than the control specimen owing to the strengthening effect. However, the NSM (no prestressing) method yielded a strengthening effect similar to that of the control specimen. It is thought that in the process of applying the NSM method, the gap between the anchorage and concrete led to a decrease in the strengthening effect.
- (5)
- Among the various strengthening methods discussed in this study, the EP method had problems at the interface between the anchorage and concrete, and the NSM method had problems with the gap between the anchorage and concrete, and with the integrated behavior of members. Furthermore, other common problems of different material characteristics were also noted depending on the manufacturer of the reinforced material. To address these problems, further investigations using a variety of strengthening methods, amounts of reinforced materials, and reinforced materials from different manufacturers are required.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Design Strength (MPa) | Unit Weight (kg/m3) | ||||||
---|---|---|---|---|---|---|---|
OPC | W | G | S | FA | GGBS | AE | |
20 | 265 | 162 | 905 | 954 | 30 | - | 2.36 |
40 | 258 | 151 | 1039 | 626 | 77 | 180 | 5.37 |
No. | Specimen | Specimen Prestressing (kN) | Strengthening Method | Strengthening Material | Strengthening Amount (ea) | Strengthening Prestressing |
---|---|---|---|---|---|---|
1 | PH4C | 280 | - | - | - | |
2 | PL4C | 140 | - | - | - | |
3 | PH2C | 280 | - | - | - | |
4 | PL2C | 140 | - | - | - | |
5 | PH4NP | 280 | near surface mounted (NSM) | carbon fiber-reinforced plastic or polymer (CFRP) | 1 | prestressing |
6 | PL4NP | 140 | NSM | CFRP | 1 | prestressing |
7 | PL2NN (H) | 140 | NSM | CFRP | 1 | - |
8 | PL2NN (S) | 140 | NSM | CFRP | 1 | - |
9 | PH4EP | 280 | external prestressing (EP) | steel | 2 | prestressing |
10 | PL4EP | 140 | EP | steel | 2 | prestressing |
11 | PH2EP | 280 | EP | steel | 2 | prestressing |
12 | PL2EP | 140 | EP | steel | 2 | prestressing |
Material Property | Steel Bar | CFRP Bar | Strands |
---|---|---|---|
Young’s modulus (GPa) | 200 | 165 | 200 |
yield stress (MPa) | 400 | - | 1597.9 |
ultimate stress (MPa) | 560 | 2750 | 1880.7 |
No. | Specimens | Crack Load (Pcr) (kN) | Yield Load (Py) (kN) | Ultimate Load (Pu) (kN) | ||||||
---|---|---|---|---|---|---|---|---|---|---|
Design * | Experimental | Displacement (mm) | Design * | Experimental | Displacement (mm) | Design * | Experimental | Displacement (mm) | ||
1 | PH4C | 96.0 | 94.5 | 5.90 | 198.7 | 218.8 | 28.14 | 227.5 | 237.6 | 79.35 |
2 | PL4C | 63.9 | 63.7 | 3.14 | 152.8 | 185.5 | 28.98 | 227.5 | 239.3 | 98.10 |
3 | PH2C | 81.3 | 83.3 | 5.58 | 194.8 | 219.6 | 33.29 | 213.7 | 233.3 | 63.03 |
4 | PL2C | 49.2 | 50.6 | 3.57 | 150.4 | 180.4 | 30.17 | 213.7 | 227.3 | 71.76 |
5 | PH4NP | 127.7 | 125.6 | 6.60 | 253.7 | 273.3 | 28.89 | 310.0 | 312.8 | 79.80 |
6 | PL4NP | 95.5 | 90.2 | 4.29 | 208.5 | 232.0 | 27.01 | 309.0 | 300.0 | 63.48 |
7 | PL2NN(H) | 56.9 | 46.2 | 3.36 | 168.4 | 198.1 | 32.32 | 227.0 | 271.4 | 82.64 |
8 | PL2NN(S) | 56.9 | 42.6 | 2.64 | 168.3 | 188.8 | 31.75 | 227.0 | 248.7 | 72.12 |
9 | PH4EP | 125.7 | 141.7 | 5.62 | 283.5 | 323.9 | 33.30 | 326.5 | 356.4 | 56.49 |
10 | PL4EP | 114.2 | 132.1 | 4.95 | 264.8 | 311.3 | 31.72 | 236.5 | 336.8 | 47.43 |
11 | PH2EP | 97.6 | 98.6 | 6.04 | 261.9 | 295.9 | 37.16 | 300.9 | 317.0 | 57.66 |
12 | PL2EP | 86.2 | 108.4 | 5.81 | 244.1 | 285.8 | 36.91 | 300.9 | 335.3 | 56.70 |
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Kim, T.-K.; Kim, S.-H.; Park, J.-S.; Park, H.-B. Experimental Evaluation of PSC Structures from FRP with a Prestressing Strengthening Method. Materials 2021, 14, 1265. https://doi.org/10.3390/ma14051265
Kim T-K, Kim S-H, Park J-S, Park H-B. Experimental Evaluation of PSC Structures from FRP with a Prestressing Strengthening Method. Materials. 2021; 14(5):1265. https://doi.org/10.3390/ma14051265
Chicago/Turabian StyleKim, Tae-Kyun, Sang-Hyun Kim, Jong-Sup Park, and Hee-Beom Park. 2021. "Experimental Evaluation of PSC Structures from FRP with a Prestressing Strengthening Method" Materials 14, no. 5: 1265. https://doi.org/10.3390/ma14051265