## 3 Testing Methodology
### Dynamic Proof Tests  
The dynamic characterization of the whole bridge was obtained through ambient vibration tests (AVTs) that were performed during all the proof load test phases as previously described (Table 1). The AVT measured the vibrations on the investigated bridge that were produced by the so-called ambient noise. For the case at hand, the excitation sources were mainly due to ground microtremors and wind, with the bridge close to traffic during the proof tests. Probably, some ambient noise was also produced by the nearby railway and roads, which were located almost 50 m from the bridge. Each AVT consisted of 15 min-long acceleration records that were sampled at 2048 Hz; AVTs started at 8:15 a.m. and finished at 2:30 p.m., so 25 AVTs were performed during the whole proof test day. Among the static tests, 5 main loading phases can be recognized and hence 5 main dynamic tests (Dyn.1-Dyn.5) can be individuated, as shown in Table 2.  
Test Dyn.1 was used to capture the modal parameters of the whole bridge (in terms of natural frequencies, damping ratios, and mode shapes) at unloaded conditions (configuration U). Tests Dyn.2 and Dyn.4 were used to investigate the changes in the bridge dynamics due to the maximum applied load (configurations C1 and C2). Tests Dyn.3 and Dyn.5, in absence of load, were performed to detect the possible variations of the structural behavior with respect to the initial unloaded configuration (Dyn.1). For the vibration measurements, PCB- and B&K-type piezoelectric uniaxial accelerometers with high sensitivity and low noise were used (Figure 5b). The sensors were connected by means of coaxial cables to both 4-channels NI 9234 and 3-channels NI 9230 acquisition modules that were mounted on an 8-slot NI cDAQ 9178 control unit that allowed a synchronous acquisition of signals. A laptop that was equipped with a dedicated LabVIEW software was also adopted to manage activities and to store data. Only one sensor configuration was adopted for all AVTs, placing 20 accelerometers throughout the bridge: 16 sensors were positioned above the deck and 4 fixed to the two downstream pylons at the level of the lower stay-cable anchorages (Figure 5a). The high number of sensors and their layout allowed the identification of the global dynamics of the bridge with a good accuracy. A further investigation of the dynamic parameters was obtained through impact load tests (ILTs) and braking load tests (BLTs), in which vibrations of much higher amplitude than those that were induced by the ambient noise were measured. ILTs were performed \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Time** & **Dynamic Test** & **Loading Phase** & **Load Configuration** \\ \hline
8:15–8:30 a.m. & Dyn.1 & L1 & U0 \\
8:30–10:00 a.m. & — & L2 to L4 & U to C1 \\
10:00–11:15 a.m. & Dyn.2 & L5 & C1 \\
11:15–12:00 a.m. & Dyn.3 & L6 & U1 \\
12:00 a.m.–12:30 p.m. & — & L7 to L9 & U to C2 \\
12:30–14:5 p.m. & Dyn.4 & L10 & C2 \\
1:45–2:15 p.m. & — & L10 to L11 & C2 to U \\
2:15–2:30 p.m. & Dyn.5 & L11 & U2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Main AVTs that were performed during the loading phases. by adopting a fully loaded truck passing over an artificial bump (Figure 5c); two bump positions were adopted (one in the mid-span, ILT 1, and one in the south lateral span, ILT 2, as shown in Figure 5a) in order to energize as many vibration modes as possible. It is worth observing that the bump was always positioned on the upstream side of the carriageway in order to excite both bending and torsional modes of the deck. ILTs were performed in two different ways: firstly, the truck passed slowly with each axis over the bump, secondly, the truck passed the bump with a constant and relatively high speed. BLTs, which were able to induce longitudinal vibrations of the deck, were executed through the same fully loaded truck that was used for ILTs, which braked on the deck approximately at mid-span (Figure 5a).