# Engineering Properties of New Claw Connectors for Alkali-Resistant Glass-Fiber-Reinforced Plastics

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Experimental Materials and Equipment

#### 2.2. Experimental Protocol

#### 2.2.1. Pull-Out Test

^{2}. According to a study by Woltman et al. on the mechanical properties of GFRP connectors with diameters ranging from 6 to 13 mm [3], the connecting rod was designed as a solid cylinder with a diameter of 10 mm for the pull-out experiments.

#### 2.2.2. Shear Test

#### 2.2.3. Durability Test

## 3. Analysis of Experimental Results

#### 3.1. Analysis of Pull-Out Test Results

#### 3.2. Analysis of Shear Test Results

#### 3.3. Analysis of Durability Test Results

## 4. Numerical Simulation

_{b0}/f

_{c0}is the ratio of the biaxial ultimate compressive strength to the uniaxial compressive ultimate strength, K

_{c}is the ratio of the second stress invariance on the tensile radial plane to that on the compressive radial plane, and µ is the viscosity coefficient.

#### 4.1. Comparative Analysis of the Experimental and Simulated Pull-Out Results

#### 4.2. Comparative Analysis of the Experimental and Simulated Shear Results

## 5. Engineering Applications

#### 5.1. Project Overview

^{2}, and the total construction area of the project is about 120,000 m

^{2}.

#### 5.2. Monitoring Program

^{2}. The building insulation exterior wall adopts the claw-type connector insulated concrete sandwich-wall-panel structure designed in this study. The anchorage depth of the claw-type connector is 35 mm, the thickness of the insulation layer is 60 mm, and the size of the exterior-leaf wall panel is 800 × 400 × 60 mm, as shown in Figure 15.

#### 5.3. Analysis of the Monitoring Results

## 6. Discussion

## 7. Conclusions

- (1)
- In the comparison experiment with the same anchorage depth and insulation thickness, the average pull-out and shear loads of the claw-type connector were 21.27 and 9.69 kN, respectively. Similarly, the average pull-out and shear loads of the rod connector were 8.70 and 2.21 kN, respectively, indicating that the anchorage and shear performances of the claw connector are better than those of the rod connector.
- (2)
- In the experiments, it was determined that the optimal cross-section parameters of the hollow connecting rod were 14 mm in outer diameter and 9.8 mm in inner diameter, and the optimal anchorage depth of the anchorage end was 3.5 cm. Moreover, the ultimate tensile strength was 24.33 kN, which was four times the standard value, whereas the shear capacity was 9.89 kN, which was 12.36 times the standard value.
- (3)
- After the durability test, the residual tensile strength of the claw connectors was 86.24% of the normal value, whereas the residual shear strength was 78.22% of the normal value after 180 days of alkali corrosion. This indicates that the FGFRP material had superior durability.
- (4)
- A numerical model of the insulation wall board was constructed using ANSYS finite-element-analysis software. The simulation results showed that the simulated pull-out and shear load–displacement curves had similar variations with those of the experimental load–displacement curves, with the deviation of the pull-out and shear limit loads less than 5%. This indicates that the numerical model can accurately predict the load–displacement relationship of the connector.
- (5)
- In the engineering application, the maximum shear displacement of the claw-type connector was 1.22 mm, and the maximum standard deviation of the displacement of the same insulation board was 0.37. Therefore, the performance of the connector is stable and has a high engineering application value.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**Physical image and dimensions of the connection parts (Unit: mm): (

**a**) Claw connectors; (

**b**) Rod connectors.

**Figure 6.**Schematic diagram of shear specimen and loading method (Unit: mm): (

**a**) Specimen-loading diagram; (

**b**) Specimen size.

**Figure 7.**Damage state of pull-out-test specimens: (

**a**) Rod connectors are pulled out; (

**b**) Lateral concrete fracture of the claw connectors; (

**c**) Cross-splitting of the upper part of the claw connectors; (

**d**) Broken anchor-end jaws.

**Figure 8.**Load–displacement curves of the pull-out test: (

**a**) Comparison of the rod and claw connectors. Tensile strengths of the rod and claw connectors at (

**b**) 3 cm anchorage depth; (

**c**) 3.5 cm anchorage depth; (

**d**) 4 cm anchorage depth; (

**e**) 4.5 cm anchorage depth; (

**f**) 5 cm anchorage depth.

**Figure 9.**Shear-specimen damage state: (

**a**) Damage state of the rod connector; (

**b**) Damage state of the claw connector.

**Figure 10.**Load–displacement curves of the shear test: (

**a**) Comparison of rod and claw connectors. Shear strengths of claw connectors of (

**b**) 12 mm outer diameter; (

**c**) 14 mm outer diameter; (

**d**) 15 mm outer diameter.

**Figure 11.**Load–displacement curves of the durability test: (

**a**) Load–displacement curve for the pull-out test; (

**b**) Load–displacement curve for the shear test.

**Figure 12.**Precast, insulated, concrete sandwich-wall-panel unit-force model: (

**a**) Grid division; (

**b**) Pull-out-force loading direction; (

**c**) Shear-force loading direction.

Material | Tensile Strength (fy/MPa) | Shear Strength (fv/MPa) | Modulus of Elasticity (Es/10 ^{5} MPa) | Elongation |
---|---|---|---|---|

FGFRP | 1086 | 281 | 0.54 | 2% |

Equipment | Specification Model | Precision | Usage |
---|---|---|---|

Standard constant-temperature-and-humidity-maintenance machine | 40 | / | Specimen maintenance |

Electronic universal-testing machine | WAW-600F | 0.5% | Strength-resistance test |

Group | Number | Insulation-Layer Thickness (mm) | Diameter of Connecting Rod (mm) | Length of Connecting Rod (mm) | Anchorage Depth (mm) |
---|---|---|---|---|---|

T0 | T0/1–T0/5 | 80 | 10 × 6 (Board type) | 140 | 30 |

T1 | T1/1–T1/5 | 80 | 10 | 140 | 30 |

T2 | T2/1–T2/5 | 80 | 10 | 150 | 35 |

T3 | T3/1–T3/5 | 80 | 10 | 160 | 40 |

T4 | T4/1–T4/5 | 80 | 10 | 170 | 45 |

T5 | T5/1–T5/5 | 80 | 10 | 180 | 50 |

Group | Number | Insulation-Layer Thickness (mm) | Outer Diameter of Connection (mm) | Inner Diameter of Connection (mm) | Anchorage Depth (mm) |
---|---|---|---|---|---|

L0 | L0/1–L0/5 | 80 | 10 × 6 (Board type) | 30 | |

L1 | L1/1–L1/5 | 80 | 10 | 0 | 30 |

L2 | L2/1–L2/5 | 80 | 12 | 6.6 | 30 |

L3 | L3/1–L3/5 | 80 | 14 | 9.8 | 30 |

L4 | L4/1–L4/5 | 80 | 16 | 12.5 | 30 |

Solution | Grams of Solute in 1 L of Water (g/L) | ||
---|---|---|---|

Ca(OH)_{2} | KOH | NaOH | |

Alkali solution | 118.5 | 4.2 | 0.9 |

Group | Ultimate Pulling Load (kN) | Average Load (kN) | Standard Deviation | ||||
---|---|---|---|---|---|---|---|

T0 | T0/1 | T0/2 | T0/3 | T0/4 | T0/5 | 8.70 | 0.12 |

8.34 | 8.75 | 8.25 | 9.02 | 9.13 | |||

T1 | T1/1 | T1/2 | T1/3 | T1/4 | T1/5 | 21.27 | 3.70 |

21.14 | 23.58 | 20.37 | 18.22 | 23.02 | |||

T2 | T2/1 | T2/2 | T2/3 | T2/4 | T2/5 | 24.28 | 1.63 |

22.19 | 24.33 | 25.09 | 23.82 | 25.98 | |||

T3 | T3/1 | T3/2 | T3/3 | T3/4 | T3/5 | 25.13 | 1.77 |

24.39 | 25.87 | 25.03 | 27.15 | 23.21 | |||

T4 | T4/1 | T4/2 | T4/3 | T4/4 | T4/5 | 26.81 | 5.30 |

23.04 | 25.68 | 28.01 | 29.83 | 27.48 | |||

T5 | T5/1 | T5/2 | T5/3 | T5/4 | T5/5 | 28.47 | 1.68 |

26.25 | 29.71 | 28.06 | 28.53 | 29.79 |

Group | Ultimate Shear Load (kN) | Average Load (kN) | Standard Deviation | ||||
---|---|---|---|---|---|---|---|

L0 | L0/1 | L0/2 | L0/3 | L0/4 | L0/5 | 2.21 | 0.05 |

1.93 | 2.05 | 2.17 | 2.52 | 2.37 | |||

L1 | L1/1 | L1/2 | L1/3 | L1/4 | L1/5 | 9.69 | 0.27 |

9.72 | 9.51 | 8.8 | 9.92 | 10.44 | |||

L2 | L2/1 | L2/2 | L2/3 | L2/4 | L2/5 | 8.82 | 4.67 |

4.68 | 8.85 | 9.91 | 10.83 | 9.82 | |||

L3 | L3/1 | L3/2 | L3/3 | L3/4 | L3/5 | 9.77 | 1.02 |

11.14 | 10.08 | 9.72 | 9.89 | 8.01 | |||

L4 | L4/1 | L4/2 | L4/3 | L4/4 | L4/5 | 9.98 | 0.48 |

10.57 | 9.99 | 9.82 | 9.20 | 10.34 |

Density (kg·m^{3}) | Ft (MPa) | Fc (MPa) | Ψ (°) | f_{b0}/f_{c0} | K_{c} | µ |
---|---|---|---|---|---|---|

2500 | 2.39 | 42.5 | 15° | 1.16 | 0.667 | 0.0005 |

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## Share and Cite

**MDPI and ACS Style**

Wang, Q.; Zhang, X.; Jing, D.; Hu, Z.; Tian, Y.; Wang, D.; Liu, W.; Tian, C.; Shi, Z.; Wang, K.
Engineering Properties of New Claw Connectors for Alkali-Resistant Glass-Fiber-Reinforced Plastics. *Materials* **2022**, *15*, 2631.
https://doi.org/10.3390/ma15072631

**AMA Style**

Wang Q, Zhang X, Jing D, Hu Z, Tian Y, Wang D, Liu W, Tian C, Shi Z, Wang K.
Engineering Properties of New Claw Connectors for Alkali-Resistant Glass-Fiber-Reinforced Plastics. *Materials*. 2022; 15(7):2631.
https://doi.org/10.3390/ma15072631

**Chicago/Turabian Style**

Wang, Qingbiao, Xu Zhang, Dongya Jing, Zhongjing Hu, Yuanyuan Tian, Dong Wang, Wenxia Liu, Chenglin Tian, Zhenyue Shi, and Keyong Wang.
2022. "Engineering Properties of New Claw Connectors for Alkali-Resistant Glass-Fiber-Reinforced Plastics" *Materials* 15, no. 7: 2631.
https://doi.org/10.3390/ma15072631