PSI - Issue 10

K. Kaklis et al. / Procedia Structural Integrity 10 (2018) 129–134 K. Kaklis et al. / Structural Integrity Procedia 00 (2018) 000 – 000

133

5

confining pressures under cyclic loads. These diagrams show the different behavior of the mortar specimens tested in uniaxial and triaxial cyclic loading. From a regression analysis, exponential relationships between the plastic strain and deviator stress and linear relationships between the plastic strain and total strain are derived, with a correlation coefficient higher than 0.93. It should be noted that the fitting results for the triaxial cyclic compression tests were derived by including all the data points from the three different confining pressures. In addition, the exponential relationships in Fig.3a are not applicable near the zero deviator stress values, since there are no plastic strains at this loading condition.

20

25

Uniaxial 2.09 MPa 3.96 MPa 6.06 MPa

ε pl = 0.61e

0.38( σ 1 - σ 3 )

R 2 = 0.96

20

ε pl = 0.88 ε R 2 = 0.99

5 Plastic strain, ε pl (x10 -3 ) 10 15

5 Plastic strain, ε pl (x10 -3 ) 10 15

Uniaxial 2.09 MPa 3.96 MPa 6.06 MPa

ε pl = 0.26e

0.36( σ 1 - σ 3 )

R² = 0.95

ε pl = 0.44 ε R² = 0.93

0

0

0

5

10

15

20

25

30

0

2

4

6

8

10

Total strain, ε (x10 -3 )

Deviator stress, σ 1 - σ 3 (MPa)

(a)

(b) Fig. 3. (a) Plastic strain vs deviator stress, (b) Plastic strain vs total strain.

Fig.4 shows the Young’s modulus variation with the total strain for all mortar specimens tested in uniaxial and triaxial compression tests under three different confining pressures. The results indicate that the Young’s modulus decreases with increasing total strain, which may due to the initial defects propagation as the load and loading cycles increased. This degradation behavior is related to some kinds of damage (microvoids and microcracks). Thereafter, the elastic modulus of specimen remains almost constant.

25000

20000

Uniaxial 2.09 MPa 3.96 MPa 6.06 MPa

15000

10000

5000

0 Young's modulus, E (MPa)

0

5

10

15

20

25

Total strain, ε (x10 -3 )

Fig. 4 . The variation of Young’s modulus with the total strain for mortar specimen s tested in uniaxial and triaxial cyclic loading under three different confining pressures.

4. Conclusions In the present study, pozzolanic lime mortar uniaxial and triaxial compression tests under unloading-reloading (cyclic loading) conditions were conducted to elucidate the stress-strain and the deformation behavior of a pozzolanic lime mortar subjected to cyclic loading. This information derived can be fully exploited when modeling the behavior of these mortars for a specific application. Experimental results indicate that a strain-softening behavior