PSI - Issue 11

Petr Stepanek et al. / Procedia Structural Integrity 11 (2018) 12–19 Petr Stepanek at al. / Structural Integrity Procedia 00 (2018) 000–000

15

4

It is evident from Fig. 3 that the elasticity modulus of the specimens was not significantly affected by any of the test exposure times and temperatures of the alkaline environment. The results oscillate around the mean value corresponding to the reference sample; see the linear approximation of results (dot lines).

50,5

50,0

49,5

49,0

20°C 40°C 60°C

48,5 Elastic modulus [GPa]

48,0

Immersion time [days]

47,5

42

92

142

192

242

292

342

Fig. 3. Dependence of GFRP-E reinforcement elasticity modulus on exposure time and temperature of solution Table 2. Tensile test results of GFRP E reinforcement immersed in alkaline solution.

Coefficient of variation [-]

Standard deviation [MPa]

Change with respect to the reference value [%]

Elastic modulus,

Coefficient of variation [-]

Standard deviation [MPa]

Change with respect to the reference value [%]

Tensile strength,

Immersion time [days]

Temperature of the alkaline solution [°C]

mean value [GPa]

mean value [MPa]

-

818

100.00

8.63

0.01

48.9

100.0

2.21

0.05

Reference sample

42 90

707 699 653 676 661 660 611 634 678 615 600 619

86.45 85.47 79.86 82.64 80.89 80.66 74.75 77.58 82.90 75.23 73.44 75.73

70.83 64.94 54.23 67.10 78.00 71.01 39.53 69.06 84.51 87.52 60.57 76.03

0.01 0.09 0.01 0.10 0.12 0.11 0.03 0.11 0.12 0.14 0.03 0.12

50.1 47.9 48.5 50.0 49.6 48.6 48.6 49.4 49.5 48.9 49.3 49.6

102.4 97.8 99.1 102.1 101.4 99.3 99.3 101.0 101.2 99.9 100.8 101.4

0.46 2.07 1.48 0.71 0.68 1.92 0.97 0.77 2.02 1.52 0.63 1.16

0.01 0.04 0.03 0.01 0.01 0.04 0.02 0.02 0.04 0.03 0.01 0.02

20

180 365

42 90

40

180 365

42 90

60

180 365

3. GFRP reinforcement behaviour under fatigue loading FRP rebar fatigue tests can be performed on bars provided with anchors for reliable anchoring of the specimen to the test device, or through concrete elements, in which the FRP reinforcement is encased in concrete. The advantage of the first type is the simple configuration of the test, but the frequent problem is the unwanted premature failure of the sample near the anchors. Anchors used in static tensile tests have to be modified for cyclic loading. The length of the concrete end blocks must be sufficient for secure anchoring of the bars by second type. For this reason, the sample sizes may be considerable, especially for bars with high tensile strength. The advantage, however, is the elimination of premature failure of the FRP reinforcement in the anchoring area. Noël and Soudki (2014) compared the fatigue life of bare GFRP bars to the fatigue life of a beam specimens reinforced with the same type of reinforcement. The beam was in the middle of the span equipped with a joint that simulated a flexural crack. The bare samples showed a fatigue life of about one level higher than for bars embedded in the beams. The authors justify this difference by the friction between the reinforcement and concrete and the different type of loading. The bare samples were loaded with an axial load, while the reinforcement in the beams