1 Introduction
2 Experimental Program
2.1 Description of Tested Slabs
Group | Specimen | Cutout aspect ratio | Cutout size (mm) | Use of CFRP sheets |
---|---|---|---|---|
Reference | S0 | None | None | None |
1 | S1 | 1:1 | 200 × 200 | None |
S2 | 2:1 | 200 × 400 | None | |
2 | S3 | 1:1 | 200 × 200 | Around cutout at tension surface |
S4 | 2:1 | 200 × 400 | Around cutout at tension surface |
2.2 Materials
Nominal diameter (mm) | Yield load (kN) | Ultimate load (kN) | Yield stress (N/mm2) | Ultimate tensile strength (N/mm2) | Ultimate strain (%) |
---|---|---|---|---|---|
10 | 35.5 | 47.8 | 450 | 610 | 16 |
Sikawrap Hex®-230C properties | |
Areal weight (±10) | 230 ± 10 (g/m2) |
Density | 1.76 (g/cm3) |
Adhesive strength on concrete | 4 (MPa) |
Density | 1.31 (Kg/lit) |
CFRP unidirectional properties | |
Tensile strength of fibers (nominal) | 4300 (MPa) |
Tensile E-modulus of fibers (nominal) | 238,000 (MPa) |
Strain at break of fibers | 1.8 (%) |
Fabric design thickness | 0.13 (mm) |
Tensile strength | 30 (MPa) |
Tensile E-modulus in flexural | 3800 (MPa) |
2.3 Sensors and Measurements
2.4 Loading Arrangement and Test Procedure
3 Experimental Results and Dissusion
3.1 Flexural Failure Mode
Group | Specimen | Ultimate load (kN) | Failure mode |
---|---|---|---|
Reference | S0 | 67 | Flexure |
1 | S1 | 56 | Flexure |
S2 | 41 | Flexure | |
2 | S3 | 62 | Rupture of CFRP sheets |
S4 | 45 | Rupture of CFRP sheets |
3.2 Rupture of CFRP Sheets
3.3 Behavior of Tested Slabs
4 Finite Element Analysis
4.1 Element Type and Meshing
4.2 Concrete
4.3 FRP Composites
4.4 Steel Reinforcement
4.5 Loads and Boundary Conditions
5 Comparison Between FE and Experimental Results
Group | Specimen | Experimental ultimate load pue (kN) | Finite element ultimate load Puf (kN) | Puf/Pue
|
---|---|---|---|---|
Reference | S0 | 67 | 65 | 0.97 |
1 | S1 | 56 | 55.2 | 0.99 |
S2 | 41 | 42 | 1.02 | |
2 | S3 | 62 | 60 | 0.97 |
S4 | 45 | 45.8 | 1.02 |
Model | Cutout size, mm | No. of layers | Layer width, mm | Area of CFRP layers, mm2
| Ultimate load (kN) | % increase ultimate load |
---|---|---|---|---|---|---|
S1 | 200 × 200 | – | – | – | 55.2 | – |
S2 | 200 × 400 | – | – | – | 42.0 | – |
S3 | 200 × 200 | 1 | 100 | 13.0 | 60.0 | 8.7 |
150 | 19.5 | 62.4 | 13.0 | |||
200 | 26.0 | 63.0 | 14.1 | |||
2 | 100 | 26.0 | 63.0 | 14.1 | ||
150 | 39.0 | 65.2 | 18.1 | |||
200 | 52.0 | 67.2 | 21.7 | |||
3 | 100 | 39.0 | 64.8 | 17.4 | ||
150 | 58.5 | 69.0 | 25.0 | |||
200 | 78.0 | 71.4 | 29.3 | |||
S4 | 200 × 400 | 1 | 100 | 13.0 | 45.8 | 9.0 |
150 | 19.5 | 47.4 | 12.9 | |||
200 | 26.0 | 48.6 | 15.7 | |||
2 | 100 | 26.0 | 49.2 | 17.1 | ||
150 | 39.0 | 51.6 | 22.9 | |||
200 | 52.0 | 52.8 | 25.7 | |||
3 | 100 | 39.0 | 51.6 | 22.9 | ||
150 | 58.5 | 54.6 | 30.0 | |||
200 | 78.0 | 57.6 | 37.1 | |||
4 | 100 | 52 | 53.4 | 27.1 | ||
150 | 78 | 58.2 | 38.6 | |||
200 | 104.0 | 64.2 | 52.9 | |||
5 | 100 | 65.0 | 56.4 | 34.3 | ||
150 | 97.5 | 63.0 | 50.0 | |||
200 | 130.0 | 69.0 | 64.3 |
5.1 Calculations of CFRP Amount Required for Strengthening
5.2 Effect of Cutouts Location
Section | Location | Model | Ultimate load, Pu (kN) | Pu/Pu (s0)
| Moment of resistance Mr (kN m) | Ult.Ld. after strengthening, Pu (kN) | % increase ultimate load |
---|---|---|---|---|---|---|---|
1 | At support (M1 = 19.5 kN m) | S0 | 65.0 | 1.00 | 19.0 | Reference | – |
2 | Hogging zone (M2 = 17.9 kN m) | S1 | 55.2 | 0.85 | 16.0 | S3 = 60.0 | 8.7 |
S2 | 42.0 | 0.65 | 11.7 | S4 = 45.8 | 9.0 | ||
3 | Quarter span (M3 = 14.6 kN m) | S1′ | 63.0 | 0.97 | 16.0 | S3′ = 63.6 | 1.0 |
S2′ | 55.0 | 0.85 | 11.7 | S4′ = 59.4 | 8.0 | ||
4 | Mid span (M4 = 11.3 kN m) | S1′′ | 64.2 | 0.99 | 16.0 | S3′′ = 64.8 | 1.0 |
S2′′ | 63.6 | 0.98 | 11.7 | S4′′ = 64.2 | 1.0 |
5.3 Effect of Changing of CFRP Configurations Around Cutouts
Model | CFRP sheets configuration around cutout | Ultimate load (kN) | % increase ultimate load |
---|---|---|---|
S1 | – | 55.2 | – |
S3 | Parallel to cutout edges | 60.0 | 8.7 |
Inclined 45° at cutout corners | 57.0 | 3.2 | |
S4 | Parallel to cutout edges | 45.8 | 9.0 |
Inclined 45° at cutout corners | 43.4 | 3.3 |