PSI - Issue 28

Flavio Stochino et al. / Procedia Structural Integrity 28 (2020) 1467–1472 Author name / Struc ural Integrity Procedia 00 (2019) 000– 0

1470 4

Temperatures ( ° C)

0.00

-20.00

-40.00

-60.00

-160.00 -140.00 -120.00 -100.00 -80.00

-0.0068

-0.0072 -0.007

-0.0074

-0.0076

Fig. 2. Time-history of temperature inside the liquid nitrogen tank.

Strain

-0.0078

-0.008

-0.0082

Fig. 3. Concrete axial strain Vs temperature on the cube inside the liquid nitrogen tank.

After emerging from liquid nitrogen, the concrete temperature tends to rise. A general temperature time trend has been detected considering all the cubes in all conditions. Figure 4 presents this trend and also the cubic polynomial expression that fits the data set. This information is relevant to understand how the successive loading cycles modify the concrete cubes temperature.

Time (h:min)

0 00:00

00:07

00:14

00:21

00:28

00:36

00:43

00:50

-20

-40

-60

-140 Temperature ( ° C) -120 -100 -80

-160

y = -3,805,906.583x 3 + 114,718.837x 2 + 4,110.364x - 173.309 R² = 0.913

-180

-200

Fig. 4. Concrete temperature time history after the emersion from the liquid nitrogen tank.

The secant elastic modulus has been calculated as the slope of the least squares linear regression of the axial stress strain diagram. Figure 5 presents a typical stress-strain diagram used to evaluate the secant elastic modulus.