PSI - Issue 62

Gallipoli Maria Rosaria et al. / Procedia Structural Integrity 62 (2024) 940–945 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1. Eigenfrequencies and corresponding mode shapes of the deck estimated by FDD. Deck Mode Direction of motion f FDD (Hz)

1 st

Vertical Bending

0.76 0.96 1.35 1.50 1.97 2.10

2 nd 3 rd 4 th 5 th 6 th

Vertical/Transverse Torsional

Vertical Bending

Vertical/Transverse Bending Torsional

Vertical Bending

Vertical/Transverse Torsional

Fig. 2. Mode shapes corresponding to the six eigenfrequencies of the deck. The red, blue and green lines refer to the X (transverse), Y (longitudinal) and Z (vertical) directions, respectively. The x-axis shows the position of the sensors for each mode and the y-axis shows the displacement values of each mode shape vector, normalised by the component with the largest modulus. The very good agreement between the results obtained with different methods (only some are given here) allows us to conclude that the estimates of the main structural characteristics of the Gravina Bridge are very reliable. Since the infrastructure was newly built, the eigenfrequencies values and their relative damping (not shown here), the mode shapes and the seismic wave propagation velocities (not shown here) can be considered as a zero-time reference point. Knowing the starting point of an infrastructure is fundamental for assessing the health state of a structure over time.