PSI - Issue 64

Amedeo Caprino et al. / Procedia Structural Integrity 64 (2024) 2149–2156 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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in early 2012, immediately after the structural assessment previously described. The system consists of six uniaxial accelerometers (acceleration transducers), sixteen linear potentiometers (displacement transducers) and seven strain gauges sensors for strain readings. Since the bridge consists of 3 spans (2 symmetrical side spans and a longer central one), it was decided to install the sensors in the following order: • PZ1, PZ2, PZ3 and PZ4 in the first right lateral span

• PZ5, PZ6, PZ7, PZ8, PZ9, PZ10 and PZ11 in the middle span • PZ12, PZ13, PZ14, PZ15 and PZ16 in the left side span.

Fig. 4. Structural Monitoring system of Ponte Nuovo bridge

Some sensors exhibited abnormal behavior related to electrical disturbances and malfunctions therefore they were excluded. However, the working sensors are installed on the beams with the most degradation (PZ4, PZ6, PZ12, PZ16). The system experienced two major shutdowns due the failure of some electrical components between June 2014 and March 2016 and between December 2018 and September 2022. Hence, in this work data only covering 2016-2022 are reported. The monitoring of static parameters enables a judgment about the deformational changes of the bridge deck beams (Fig. 5). The totality of the sensors and their displacements show a clear seasonal cyclic behavior strongly related to thermal variations. It can be seen that the maximum displacements measured in the centerline at the girders are very small, on the order of a tenth of a millimeter (0.3 to 0.4 mm) and inversely follow temperature variations. In fact, the analysis of displacements as a function of temperature shows a decrease in displacements (reduction in the distance between the measurement bases) at high temperatures (warm season) and a return to the original distance between the measurement bases during the winter season. For sensors PZ4 (second beam on the right span) and PZ12 (second beam on the left span), installed on two of the most damaged beams, there is a slight accumulation of deformation on the order of tenths of a millimeter (about 0.15 mm per year). For the other sensors, on the other hand, there is an almost perfect correlation between displacements and thermal changes indicative of reversible phenomena, with no cumulative deformation phenomena typical of progressive structural damage. Therefore, the presence of severe worsening of damage phenomena can likely be ruled out based on the recorded data. The substantial stability of most of the measured parameters allowed to maintain the bridge in operation, whereas the strain accumulation recoded by the sensors (PZ4 and PZ12) installed on the most damaged girders, together with the structural assessment carried out, indicates some critical issues for the health of the bridge and makes repair work essential.