PSI - Issue 44

Leqia He et al. / Procedia Structural Integrity 44 (2023) 1594–1601 Lequia He et al./ Structural Integrity Procedia 00 (2022) 000 – 000

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and 0.25m in thickness) and is prestressed by two external tendons. The tendons are formed by two bundles of 12 xΦ 15.2mmmono-strands grouted inside the galvanized steel tubes. The central part of the deck over the river simply rests on the cross beams, while the side parts of the deck hang down freely between the cross beams and the abutments. Operational modal analysis was performed with a total of 22 nodes that were measured on the bridge deck. In Figure 2 it is represented the setup for the measurement nodes. The acquisition system used was the GMSplus wireless measurement system of the GeoSIG company, sampling at 200 Hz. Two reference sensors and two roving sensors were used for a total of 11 experimental setups. For each setup, the reference sensors were fixed in Nodes 2 and 16. The choice of the reference nodes was derived from a study of the numerical modal characteristics as predicted by a preliminary FE model. The roving sensors, instead, were moved from the right side of the bridge to the left side of the bridge. The roving sensors were placed adjacent to the reference ones at the reference nodes. Each sensor unit was embedded with the tri-axial MEMS accelerometer, which allowed for the synchronous record of the structural vibration responses in all the vertical, transverse, and longitudinal directions. The measurements period was 15 min for each experimental setup. During the testing period, the bridge was under ambient excitation, which included mild winds and low-density pedestrians. In particular, the traffic situations can be classified as ‘individual pede strians and small groups’ (Feldman, 2008).

Fig. 2. Deployment of the measurement nodes, labelled from 1 to 22: top view (a), front view (b), sections (c). The reference nodes are Nodes 2 and 16 (units in cm).