PSI - Issue 64

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

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Fig. 2. Location of thermographic cameras outside (left) and transducer lines inside (right) the Containment Structure.

Fig. 3. Relative pressure inside the Containment Structure.

4. Evaluation of test results The numerical model, developed for a preliminary assessment of the design requirements imposed on the CS, was also used to filter out the associated uncontrolled thermal strains and displacement that took place during pressure test. Kim et al. (2018) and Wang et al. (2019) warn about the influence of thermal variations in the evaluation of structural behavior during pressure tests. Cheng et al. (2022) carry out a study with similar characteristics to the present one also for a CANDU Reactor Building using de ABAQUS program. However, these authors mainly analyze strains. Here, emphasis is placed on displacements whose experimental measurements are less affected by local conditions. The temperature records obtained for both the internal and external surfaces of the CS were imposed on the inner and outer surfaces of the model, considering a Fourier expansion along the circumferential direction and step functions in the vertical direction in order to interpolate the records over the entire surfaces (Ceballos et al, 2019). The initial value of the temperature of all nodes across the thickness of the CS walls and buttresses was initially assumed to vary linearly between the external nodes on each section. Then, the thermally induced strains and displacements at all nodes of the model were calculated until they were independent of the distribution of initial temperature values assumed at the beginning of the analysis. This state was reached at the 12 th day, and was adopted as the initial temperature for all nodes. The computed strains and displacements thereafter were taken as the thermally induced displacements and strains to be subtracted from the measured values in order to obtain those caused by the prescribed internal pressure. For the evaluation of the test results, the elastic parameters of the cylindrical wall concrete are expected to be different from those of the external dome due to their different thickness, construction procedure and exposition to the sun radiation over so many years. Two different uniform values are assumed to compare measured and computed deformations for the dome and the cylindrical wall. This criterion is also supported by the results of the pressure test performed in August 1981 prior to starting operation of the plant. In that occasion the measured displacements of the dome were appreciably smaller than those predicted by design calculations; in fact, the radial displacement calculated with the actual adjusted model is 24% lower than that measured in the last test. It should be noted that in the 1981