Basic Mechanical Properties of Duplex Stainless Steel Bars and Experimental Study of Bonding between Duplex Stainless Steel Bars and Concrete
Abstract
:1. Introduction
2. Duplex Stainless Steel Bar Room Temperature Tensile Test
2.1. Specimen Design
2.2. Experimental Method and Procedure
2.3. Analysis of Experimental Results
2.3.1. Analysis of the Fracture Position of Duplex Stainless Steel Bars
2.3.2. Stress–Strain Curve Analysis of Duplex Stainless Steel Bars
2.3.3. Duplex Stainless Steel Bar Basic Mechanical Properties Index
2.4. Recommendations for the Basic Mechanical Properties of Duplex Stainless Steel Bars
- Hypothesis that : the measured data (random variable ) follows a normal distribution.
- Sort the measured data from smallest to largest and calculate the measured frequency .
- Calculate the theoretical distribution of the distribution function .
- Calculate the theoretical frequency and the theoretical frequency .
- Calculate the value
- Look up the table, calculate , and make statistical judgments: if
- k: number of groups; and,
- r: estimate the number of parameters, which is 2 in this article.
3. Bonding Performance Test
3.1. Experimental Overview
3.1.1. Specimen Design and Production
3.1.2. Loading Device
3.2. Analysis of Test Results
3.2.1. Forms of Damage
- Duplex stainless steel bar pull-out damage
- 2.
- Concrete splitting damage
3.2.2. Bond Stress
- : Bond stress;
- : Duplex stainless steel bar diameter (mm);
- : The length of the bonded section of duplex stainless steel bars (mm); and,
- : Test load.
3.2.3. The Influence of Various Factors on the Bonding Performance
- The effect of concrete strength on bonding performance
- 2.
- The effect of duplex stainless steel bar diameter on bonding performance
- 3.
- The influence of the ratio of concrete cover to reinforcing steel diameter on bonding performance
- 4.
- Effect of relative anchorage length on bonding performance
4. Regression Model of Bond Stress
5. Summary and Conclusions
- The tensile process of duplex stainless steel bars is different from that of ordinary steel bars, which can be divided into three stages: elastic stage, strengthening stage, and necking stage. The mechanical properties of duplex stainless steel bars are stable, and their strength is high. Additionally, there is no significant yield strength, but the elastic modulus is low.
- Duplex stainless steel reinforcement center pull-out specimens have two forms of damage, respectively, pull-out damage and concrete splitting damage. In duplex stainless steel bars in the extraction process, its raised ribs will produce squeezing force on the surrounding concrete matrix. The squeezing force causes tension in the surrounding concrete. When this tensile stress exceeds the tensile strength of the concrete, the specimen cracks internally, which involves cracks developing from the inside out. When the tensile strength of the concrete specimen is small, the internal cracks develop to the surface of the specimen and splitting damage occurs. When the tensile strength of concrete is higher, no cracks are visible on the surface of the specimen, the concrete in front of the reinforcing rib is crushed, and the reinforcing bar is pulled out, at which time the specimen undergoes pull-out damage.
- The higher the strength of the concrete, the greater the bond stress between the duplex stainless steel reinforcement and the concrete, and the bond stress is proportional to the square root of the concrete strength. The change in the diameter of duplex stainless steel reinforcement has an effect on the damage form of the specimen: the larger the diameter of duplex stainless steel reinforcement the lower the bond stress. The increase in the ratio of concrete cover to rebar diameter can enhance the crack resistance of the specimen: when the ratio of concrete cover to rebar diameter is less than 4.5 and when the concrete has a small tensile strength, the specimen is prone to splitting damage and the bond stress increases with the ratio of concrete cover to rebar diameter; when the ratio of concrete cover to rebar diameter is greater than 4.5 and when the concrete has a higher tensile strength, the specimen is prone to pull-out damage and bond stress remains basically unchanged. Because the duplex stainless steel reinforcement has higher strength, which greatly enhances the bond strength with concrete and duplex stainless steel reinforcement, bond stress is more uniformly distributed along the anchorage length direction, so that, when the relative anchorage length increases, the mechanical bite between the duplex stainless steel reinforcement and concrete increases, and the bond strength increases accordingly.
- The duplex stainless steel bar bond stress expression that is established by regression analysis can better fit the test value and predicted value for different concrete strengths, the duplex stainless steel bar diameters, the ratio of concrete cover to bar diameter, relative anchorage length, and the formula established, and the test results are in good agreement. It shows that the bond stress formula is scientific and reliable.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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Model Number | C | Si | Mn | P | S | Ni | Cr | Mo | Cu | N |
---|---|---|---|---|---|---|---|---|---|---|
1.4362 | 0.03 | 1.0 | 2.5 | 0.035 | 0.03 | 3.0–5.5 | 21.5–24.5 | 0.05–0.60 | 0.05–0.60 | 0.05–0.20 |
Number | Diameter/mm | Original Scale Distance/mm | Total Length/mm | Number of Test Roots |
---|---|---|---|---|
L12 | 12 | 60 | 250 | 32 |
L16 | 16 | 80 | 300 | 35 |
L25 | 25 | 125 | 450 | 33 |
L28 | 28 | 140 | 450 | 39 |
L32 | 32 | 160 | 500 | 38 |
Diameter (mm) | Number of Specimens | Tensile Strength (MPa) | Yield Strength (MPa) | Elastic Modulus (105 MPa) | Elongation after Break (%) | ||||
---|---|---|---|---|---|---|---|---|---|
Average Value | Standard Deviation | Average Value | Standard Deviation | Average Value | Standard Deviation | Average Value | Standard Deviation | ||
12 | 32 | 842 | 9.32 | 636 | 23.92 | 1.56 | 0.06 | 33.00 | 1.43 |
16 | 35 | 768 | 5.96 | 531 | 16.67 | 1.56 | 0.08 | 36.39 | 2.43 |
25 | 33 | 760 | 9.21 | 542 | 26.94 | 1.40 | 0.11 | 34.13 | 1.25 |
28 | 39 | 743 | 9.19 | 514 | 17.21 | 1.38 | 0.09 | 39.53 | 1.21 |
32 | 38 | 748 | 4.30 | 527 | 15.48 | 1.39 | 0.13 | 36.89 | 0.75 |
Rebar Type | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation after Break (%) |
---|---|---|---|
500 MPa grade ordinary carbon steel bars | 630 | 500 | 15 |
Duplex stainless steel bars | 750 | 514 | 33 |
Category | Number of Specimens | Test Results | ||
---|---|---|---|---|
Tensile strength | 177 | 5.36 | 5.891 | Accepted |
Elongation after break | 95 | 12.3 | 12.69 | Accepted |
Modulus of elasticity | 175 | 5.62 | 7.85 | Accepted |
Yield strength | 175 | 10.33 | 12.92 | Accepted |
Indicators | Tensile Strength (MPa) | Yield Strength (MPa) | Modulus of Elasticity (×105 MPa) | Elongation after Break (%) |
---|---|---|---|---|
Average value | 755 | 529 | 1.43 | 36.74 |
Standard deviation | 9.82 | 10.02 | 0.07 | 1.92 |
Coefficient of variation | 0.01 | 0.02 | 0.05 | 0.05 |
Standard value | 739 | 513 | 1.43 | 33.58 |
Concrete Strength | Water-Cement Ratio | Sand Rate (%) | Cement (kg/m3) | Water (kg/m3) | Sand (kg/m3) | Coarse Aggregate (kg/m3) | Admixtures |
---|---|---|---|---|---|---|---|
C25 | 0.68 | 38 | 287 | 195 | 729 | 1189 | Not used |
C30 | 0.60 | 37 | 325 | 195 | 696 | 1184 | Not used |
C40 | 0.49 | 36 | 398 | 195 | 651 | 1156 | Not used |
Number | Concrete Strength | Concrete Compressive Strength, fc′ (MPa) | Diameterd/mm | c/d | la/d | Specimen Side Length/mm | Number of Test Pieces |
---|---|---|---|---|---|---|---|
C25R16T4.5L5 | C25 | 28 | 16 | 4.5 | 5 | 160 | 3 |
C30R16T4.5L5 | C30 | 38.1 | 16 | 4.5 | 5 | 160 | 3 |
C40R16T4.5L5 | C40 | 43.7 | 16 | 4.5 | 5 | 160 | 3 |
C30R12T4.5L5 | C30 | 38.1 | 12 | 4.5 | 5 | 120 | 3 |
C30R25T4.5L5 | C30 | 38.1 | 25 | 4.5 | 5 | 250 | 3 |
C30R16T3.3L5 | C30 | 38.1 | 16 | 3.3 | 5 | 120 | 3 |
C30R16T5.8L5 | C30 | 38.1 | 16 | 5.8 | 5 | 200 | 3 |
C30R16T7.3L5 | C30 | 38.1 | 16 | 7.3 | 5 | 250 | 3 |
C30R16T4.5L3 | C30 | 38.1 | 16 | 4.5 | 3 | 160 | 3 |
C30R16T4.5L4 | C30 | 38.1 | 16 | 4.5 | 4 | 160 | 3 |
C30R16T4.5L6 | C30 | 38.1 | 16 | 4.5 | 6 | 160 | 3 |
Number | Form of Damage | Damage Load (KN) | Bond Stress (MPa) |
---|---|---|---|
C25R16T4.5L5-1 | Pull-out | 73.3 | 18.2 |
C25R16T4.5L5-2 | Pull-out | 66.3 | 16.5 |
C25R16T4.5L5-3 | Pull-out | 70.3 | 17.5 |
C30R16T4.5L5-1 | Pull-out | 84.0 | 20.9 |
C30R16T4.5L5-2 | Pull-out | 79.6 | 19.8 |
C30R16T4.5L5-3 | Pull-out | 80.4 | 20.0 |
C40R16T4.5L5-1 | Splitting | 88.4 | 22.0 |
C40R16T4.5L5-2 | Pull-out | 88.8 | 22.1 |
C40R16T4.5L5-3 | Pull-out | 89.1 | 22.2 |
C30R12T4.5L5-1 | Pull-out | 44.0 | 19.5 |
C30R12T4.5L5-2 | Pull-out | 46.9 | 20.7 |
C30R12T4.5L5-3 | Splitting | 42.0 | 19.6 |
C30R25T4.5L5-1 | Splitting | 207.1 | 20.1 |
C30R25T4.5L5-2 | Pull-out | 179.4 | 19.3 |
C30R25T4.5L5-3 | Splitting | 190.6 | 19.4 |
C30R16T3.3L5-1 | Splitting | 61.9 | 15.8 |
C30R16T3.3L5-2 | Splitting | 69.9 | 16.8 |
C30R16T3.3L5-3 | Splitting | 64.7 | 16.1 |
C30R16T5.8L5-1 | Pull-out | 81.4 | 20.3 |
C30R16T5.8L5-2 | Pull-out | 77.7 | 19.3 |
C30R16T5.8L5-3 | Pull-out | 83.4 | 20.8 |
C30R16T7.3L5-1 | Pull-out | 80.3 | 20.0 |
C30R16T7.3L5-2 | Pull-out | 78.9 | 19.6 |
C30R16T7.3L5-3 | Pull-out | 82.4 | 20.5 |
C30R16T4.5L3-1 | Pull-out | 45.0 | 18.7 |
C30R16T4.5L3-2 | Pull-out | 46.6 | 19.3 |
C30R16T4.5L3-3 | Pull-out | 44.9 | 18.6 |
C30R16T4.5L4-1 | Pull-out | 66.2 | 19.6 |
C30R16T4.5L4-2 | Pull-out | 62.4 | 19.4 |
C30R16T4.5L4-3 | Pull-out | 61.1 | 19.0 |
C30R16T4.5L6-1 | Pull-out | 101.3 | 21.0 |
C30R16T4.5L6-2 | Pull-out | 107.1 | 22.2 |
C30R16T4.5L6-3 | Pull-out | 100.3 | 20.8 |
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Li, Q.; Cui, Y.; Wang, J. Basic Mechanical Properties of Duplex Stainless Steel Bars and Experimental Study of Bonding between Duplex Stainless Steel Bars and Concrete. Materials 2021, 14, 2995. https://doi.org/10.3390/ma14112995
Li Q, Cui Y, Wang J. Basic Mechanical Properties of Duplex Stainless Steel Bars and Experimental Study of Bonding between Duplex Stainless Steel Bars and Concrete. Materials. 2021; 14(11):2995. https://doi.org/10.3390/ma14112995
Chicago/Turabian StyleLi, Qingfu, Yunqi Cui, and Jinwei Wang. 2021. "Basic Mechanical Properties of Duplex Stainless Steel Bars and Experimental Study of Bonding between Duplex Stainless Steel Bars and Concrete" Materials 14, no. 11: 2995. https://doi.org/10.3390/ma14112995
APA StyleLi, Q., Cui, Y., & Wang, J. (2021). Basic Mechanical Properties of Duplex Stainless Steel Bars and Experimental Study of Bonding between Duplex Stainless Steel Bars and Concrete. Materials, 14(11), 2995. https://doi.org/10.3390/ma14112995