PSI - Issue 64

Alessandra De Angelis et al. / Procedia Structural Integrity 64 (2024) 327–334 De Angelis et al./ Structural Integrity Procedia 00 (2019) 000 – 000

332 6

=( +1 − )/

(1)

Table 3. Evolution of the natural frequencies during the AVTs

AVT n. 1

AVT n. 2

AVT n.3

Comparison

Mode

f [Hz]

f [Hz] 2.466 3.296 3.833 6.543 10.059

f [Hz] 2.099 2.913 3.027 5.989 9.195

D f1-2 [%]

D f2-3 [%]

1 2 3 4 5

3.19 3.89 4.16 8.69 9.88

-22.70 -15.27 -7.86 -24.71

-14.88 -11.62 -21.03 -8.47

1.81 -8.59 As can be seen, for each mode of vibration, the resonance frequencies decrease from AVT n. 1 to AVT n.3, because of the overall stiffness decrement due to the removal of the internal partitions (AVT n. 2) and the removal of infill walls at the staircase and some infills at the semi-basement.

Fig. 6. Evolution of the mode shapes during AVTs

Fig. 6 depicts the evolution of the first five mode shapes for each test. As can be seen, during all the stages, the first mode corresponds to the first translational mode in transverse direction. However, in the as-built condition (AVT n. 1) there is rotation component instead after the removal of internal partition walls (AVT n. 2) the shape is purely translational. The second and third mode that are rototranslational in the as built condition (AVT n.1) became the first translation mode in the longitudinal direction and the torsional mode, respectively, during the other tests (AVT n.2 and AVT n.3). Moreover, it can be seen that the mode shapes of the higher modes, i.e., fourth and fifth mode, are always characterized by an IP floor deformation, with higher modal displacements at mid-length of the floors and lower displacements at the ends. This effect is more visible in the last two AVTs. In general, it is possible to say that the removal of the internal partitions (AVT n. 2) has led to a regularization of the mode shapes eliminating the rotational components coupled to the translational modes. Whereas with AVT n.3, following the removal of the infill only along the staircase, irregularities in the stiffness distribution are again introduced leading to the presence of rotational components. 3. Model updating Experimentally identified dynamic behavior can be used for multiple purposes, including calibration of numerical models that can be used to develop seismic analysis and evaluation of buildings. The calibration process is based on