PSI - Issue 28

Jamal A. Abdalla et al. / Procedia Structural Integrity 28 (2020) 1295–1302 Author name / Structural Integrity Procedia 00 (2019) 000–000

1298

4

(a)

(b) Fig. 2. (a) Instrumented test specimen with strain gauges; (b) mounted test specimen

3. Results and Discussions 3.1. Bond stress-slip curves and other relationships

The relationship between shear stress ( ), slip ( ) and distance ( ) is illustrated in charts along with the load-strain and load-extension curves as shown for two specimens, 60-P-L4 and 20-P-L4 in Fig. 3 and Fig. 4. The two specimens were cast from concrete with compressive strength of 60 MPa and 20 MPa and have untreated plain AA plate with bonded length of 200 mm. Concrete prisms strengthened with AA-R plates exhibits higher bond stress, slip and strains compared to the AA-P strengthened samples since it takes much longer for the debonding to occur in case of AA-R samples, as the bond is strong between the plate and concrete. It can be shown from Fig. 3 and Fig. 4 that for the AA P, the maximum shear stress and maximum load for the 60 MPa and 20 MPa concrete strength samples is approximately the same, with a shear stress value of around 1.0 MPa for both samples and a failure load of 7.07 kN and 5.75 kN, respectively. This shows that the concrete strength has a negligible effect in increasing the shear stress and ultimate load in the case of AA-P plates, since the failure occur in the plate adhesive interface and not in concrete except in a few cases due to stress concentration when the bonded length is short with low concrete strength.

(a)

(b)

(c)

1

0 0.01 0.02 0.03 0.04 0 100 200 300 400 500

6000

SG1 SG2 SG3 SG4

2000 4000

0.5

Slip (mm)

Load (kN)

Stress (MPa)

0

0

0

100

200

0

100

200

0

200 400 600

Distance (mm)

Distance (mm)

Strain (  )

(d)

(e)

(f)

1

6000

Strain(  )

4000

0.5

0 2000

Load(kN)

Stess (MPa)

0

0

0.02

0.04

0

100

200

0

1

2

Slip (mm)

Distance (mm)

Extension (mm)

0.2P

0.4P

0.6P

0.8P

1.0P

Fig. 3. Specimen 60-P-L4 (a) stress-distance; (b) slip-distance; (c) load-strain; (d) shear stress-slip (e) strain-distance; (f) load-extension.