PSI - Issue 64

Federico Pinto et al. / Procedia Structural Integrity 64 (2024) 766–773 Author name / Structural Integrity Procedia 00 (2019) 000–000

768

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Table 1. Initial estimate of the thermo-mechanical parameters of concrete. Parameter Unit Value

Description

Elastic modulus of concrete

kN/m 2

E

4.00  10 7

0.15 2400

Poisson's coefficient Density of concrete

ν



kg/m 3

 

1/°C

Coefficient of thermal expansion

1.00  10  5

J/kg/°C W/m/°C

880 1.70

Specific heat capacity Thermal conductivity

c p

k

3. Instrumentation The numerical model includes the evaluation of the transient thermal behavior based on measured temperatures of the external surface that started two weeks before the actual pressurization process. These temperatures were obtained on the outer surface of the structure through 7 thermographic cameras (TC) that cover the upper dome and the complete perimeter of the cylindrical shell. Fig. 2 (left) shows the location of these cameras. The cylindrical wall was recorded by cameras TC1 through TC4 for the four quadrants, the dome by TC5 camera from the E direction, while the TC6 and TC7 cameras covered wall sectors with reduced visibility from the NE direction. In the area of permanent shadow produced by the proximity to the Service Building (thick line on the left side of Fig. 2), five temperature transducers were placed. Displacements induced by the internal pressure were recorded by means of 19 LVDTs that were fixed to both the containment and to the internal structure. Strains and temperature changes of the internal surface of the CS were also measured through 6 strain gauges and 24 temperature transducers. Fig. 2 (right) shows the position of lines L1, L2, L3 and L4 on which these transducers were located, while Table 2 shows their elevation. The upper face of the base slab is at level 93.80 m, while the free-soil surface is at level 100.00 m. The radial displacement of the spherical dome was measured only at the apex. Fig. 3 shows the evolution over time of the relative atmospheric pressure inside the CS with respect to the atmospheric pressure outside. Pressurization begun approximately on day 15: the time to reach a pressure of 43.8 kPa (6.35 psi) was 0.90 days (21.6 hours), which was then kept constant for 2.20 days (52.8 hours). The increase in pressure was then resumed up to 126.0 kPa (18.28 psi) in 1.41 days (33.8 hours), and then kept constant for 0.88 days (21.1 hours). Finally, the complete depressurization took place in 2 days (48 hours). The final/residual values were determined based on results of the 3 (72 hours) days after complete depressurization.

Table 2. Location of transducers on the Containment Structure. Dome Line L1

Line L2

Line L3

Line L4

Displacement transducers

Elev. [m]

Elev. [m]

Elev. [m]

Elev. [m]

Elev. [m]

Temp. trans.

Disp. trans.

Temp. trans.

Disp. trans.

Temp. trans.

Disp. trans.

Temp. trans.

Disp. trans.

Temp. trans.

Disp. trans.

TPI01 MD01 145.11 TPI11 MD11 100.00 TPI21 MD21 98.20

TPI31 MD31 100.00 TPI41 MD41 101.80 TPI12 MD12 106.71 TPI22 MD22 105.41 TPI32 MD32 106.71 TPI42 MD42 108.34 TPI13 MD13 112.50 TPI23 MD23 112.50 TPI33 MD33 112.50 TPI43 MD43 113.90 TPI14 MD14 117.45 TPI24 MD24 120.50 TPI34 MD34 117.45 TPI44 MD44 119.91 TPI25 MD25 128.12 TPI45 MD45 128.83 Strain gauges

Elev. [m]

Elev. [m]

Elev. [m]

Elev. [m]

Elev. [m]

Temp. trans. TPI02 TPI02

Strain trans.

Temp. trans.

Strain trans.

Temp. trans. TPI22 TPI23

Strain trans.

Temp. trans.

Strain trans.

Temp. trans. TPI42 TPI43

Strain trans.

SG01 145.11 SG02 145.11

SG22 105.91 SG23 113.00

SG42 108.84 SG43 114.00