Severely Damaged Reinforced Concrete Circular Columns Repaired by Turned Steel Rebar and High-Performance Concrete Jacketing with Steel or Polymer Fibers
Abstract
:1. Introduction
2. High-Performance Fiber Reinforced Concrete to Repair RC Components
2.1. Concrete Mix Design
2.2. Concrete Mechanical Characterization
2.2.1. Compression Test
- (1)
- The concrete with steel fibers (UHS) showed an increase in strength as the fiber volume fraction increased (Figure 1a). That phenomenon was not constant but it tended to reduce increasing the fiber percentage.
- (2)
- The concrete with polymer fibers (UHP) presented a decrease in the strength when the fiber volume fraction increased (Figure 1b).
2.2.2. Bending Tests
- (1)
- Concrete with 2% volume fraction of steel fibers because this fiber content is a typical value used in the literature [38,39,40,41,42] that considerably improves the concrete mechanical characteristics. A greater volume content produces a further increase in the compressive and tensile strength of the concrete but causes segregation during concrete mix and casting.
- (2)
- Concrete with 4% volume fraction of polymer fibers to guarantee concrete workability and cast of the new concrete part and greater possible values of ductility measured on the load-CTOD curve, tensile strength, and the equivalent strength. This volume fraction is equivalent to one proposed in the literature [38,39,40,41,42] and was studied for the first time in the present study.
2.3. Code Equation to Determine the Tensile Strength
3. Design Equation for the HPFRC Concrete Jacketing
4. Case Study
4.1. Longitudinal Rebar Substitution
4.2. Concrete Restoration by HPFRC Jacket
5. Experimental Validation of the Repair Strategy
5.1. Test Setup
5.2. Test Protocol
6. Test Results
6.1. Columns Hysteretic Response
6.2. Stiffness Evolution
6.3. Dissipated Energy
6.4. Hysteretic Damping and Force Reduction Factor
6.5. Shear Strength of Columns
6.6. Jacket Strains
6.7. Damage to the Columns
7. Numerical Investigation
7.1. Numerical Fiber Models and Section Analisys
- (1)
- (2)
- The experimental stress-strain curve for the UHS concrete used to repair the column R16-UHS (region P2 of the BB section, Table 7);
- (3)
- The experimental stress-strain curve for the UHP concrete used to repair the column R16-UHP (region P2 of the BB section, Table 7);
- (4)
- The skeleton curve that approximates the experimental curves obtained for the turned and unturned steel rebar in Figure 8.
7.2. Maximum Flexural Strength
8. Conclusions
Author Contributions
Funding
Conflicts of Interest
References
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Specimen | Vol (%) | Rcm (MPa) | SD | Fiber | Specimen Failure Mode |
---|---|---|---|---|---|
No fiber | 0 | 93.6 | 2.6 | | |
Steel | 1 | 100.9 | 3.0 | ||
Steel | 2 | 110.2 | 2.7 | ||
Steel | 3 | 116.3 | 3.7 | ||
No fiber | 0 | 75.7 | 4.0 | | |
Polymer | 2 | 51.4 | 3.9 | ||
Polymer | 4 | 56.9 | 4.2 |
Steel Fiber Volume Fraction | feq2 (MPa) | fFtu (MPa) | fctm (MPa) |
---|---|---|---|
2% Mean (Min.) | 12.2 (12.2) | 4.1 (4.1) | 4.9 |
3% Mean (Min.) | 15.1 (14.8) | 5.0 (4.9) | 5.0 |
Polymer Fiber Volume Fraction | feq2 (MPa) | fFtu (MPa) | fctm (MPa) |
---|---|---|---|
2% Mean (Min.) | 6.1 (5.7) | 2.0 (1.9) | 3.5 |
4% Mean (Min) | 8.2 (7.1) | 2.7 (2.4) | 3.7 |
Column | Lt | ϕt | Concrete Jacket | Trans. Steel Reinforced |
---|---|---|---|---|
P16A, P16B | 0 | 18 | No fibers | ϕ 4/60 |
R16-UHS | 250 | 15 | 2% vol steel fiber | - |
R16-UHP | 250 | 15 | 4% vol Polymer fiber | - |
Specimen | Load Direction | μΔ | BSmax (kN) | Ktang (kN/m) | K1sec (kN/m) |
---|---|---|---|---|---|
P16B | Pos. | 6 | 229.0 | 22,485.5 | |
Neg. | >7 | –229.0 | 53,846.1 | ||
R16-UHS | Pos. | >6 | 233.0 | - | 22,011.8 |
Neg. | >7 | –227.0 | 53,846.2 | ||
R16-UHP | Pos. | >6 | 215.0 | 21,271.7 | |
Neg. | >7 | –229.6 | 51,851.85 |
Column | R16-UHS | R16-UHP |
---|---|---|
VRd,cc | 29.2 | 29.2 |
VRd,cj (VRd,cjmin) | 254.5 (234.5) | 230.2 (206.1) |
VRd (VRdmin) | 283.7 (263.7) | 259.4 (235.3) |
BSmax | 186.4 | 172.0 |
Header | P16B | R16-UHS | R16-UHP | Fiber Sections | Concrete Stress–Strain Curves |
---|---|---|---|---|---|
zc_num (mm) | 130.8 | 78.9 | 107.2 | | |
Mmax_num (kNm) | 276.7 | 267.6 | 241.5 | ||
Fmax_num (kN) | 237.1 | 229.3 | 207.6 | ||
BSmax (kN) | 229.0 | 233.0 | 215.0 |
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Xue, J.; Lavorato, D.; Bergami, A.V.; Nuti, C.; Briseghella, B.; Marano, G.C.; Ji, T.; Vanzi, I.; Tarantino, A.M.; Santini, S. Severely Damaged Reinforced Concrete Circular Columns Repaired by Turned Steel Rebar and High-Performance Concrete Jacketing with Steel or Polymer Fibers. Appl. Sci. 2018, 8, 1671. https://doi.org/10.3390/app8091671
Xue J, Lavorato D, Bergami AV, Nuti C, Briseghella B, Marano GC, Ji T, Vanzi I, Tarantino AM, Santini S. Severely Damaged Reinforced Concrete Circular Columns Repaired by Turned Steel Rebar and High-Performance Concrete Jacketing with Steel or Polymer Fibers. Applied Sciences. 2018; 8(9):1671. https://doi.org/10.3390/app8091671
Chicago/Turabian StyleXue, Junqing, Davide Lavorato, Alessandro V. Bergami, Camillo Nuti, Bruno Briseghella, Giuseppe C. Marano, Tao Ji, Ivo Vanzi, Angelo M. Tarantino, and Silvia Santini. 2018. "Severely Damaged Reinforced Concrete Circular Columns Repaired by Turned Steel Rebar and High-Performance Concrete Jacketing with Steel or Polymer Fibers" Applied Sciences 8, no. 9: 1671. https://doi.org/10.3390/app8091671
APA StyleXue, J., Lavorato, D., Bergami, A. V., Nuti, C., Briseghella, B., Marano, G. C., Ji, T., Vanzi, I., Tarantino, A. M., & Santini, S. (2018). Severely Damaged Reinforced Concrete Circular Columns Repaired by Turned Steel Rebar and High-Performance Concrete Jacketing with Steel or Polymer Fibers. Applied Sciences, 8(9), 1671. https://doi.org/10.3390/app8091671