PSI - Issue 44

Andrea Nettis et al. / Procedia Structural Integrity 44 (2023) 1996–2003 Andrea Nettis et al. / Structural Integrity Procedia 00 (2022) 000 – 000 5 5) Deformation parameters are calculated for the investigated bridge. The first parameter is the global deformation velocity (GDV) which is equal to the average values of for the selected bridge (Equation (1). The GDV is considered to resume the intensity of the global displacement affecting the whole structure. The second parameter is the differential deformation velocity (DDV) (Equation (2) measuring the presence and intensity of ongoing differential displacement involving different parts of the bridge having relevant potential for inducing structural and non-structural damages. Additionally, a “population” parameter (POP) is calculated as the ratio between the number of bridge regions including at least one PS divided by the total number of bridge regions. This parameter informs the user about the spatial density of PS with reference to the bridge footprint. = | ( )| (1) = (| ( ) − ( )|) (2)

2000

Fig. 1. Case-study highway network in Roma and interferometry analysis (maps of displacement velocity of the PS) for two selected areas subjected to subsidence.

Fig. 2. Population attribute (POP) for the bridges detected in the case-study road network (a) and examples of bridges characterised by different POP values (b and c).

3.3. Discussion on PS spatial density on bridges The first discussion concerns the potential of MTInSAR (according to the abovementioned algorithm) in performing network-scale bridge portfolio observation. For this purpose, the spatial density of PSs on the case-study bridge footprints is assessed by observing the POP parameter. The map in Fig. 2a shows the bridge-specific POP parameter, which can be assumed as a proxy of the adequacy of the PS geospatial distribution to uniformly cover the footprints of the analysed bridges. For the case-study road network, 71% of the analysed bridge footprints are