PSI - Issue 84

Mirza Adeel Zeb et al. / Procedia Structural Integrity 84 (2026) 248–255

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The analysis clearly shows that largest and most destructive landslide events are not randomly distributed but are concentrated within specific geological zones characterized by the presence of extensive mass movements. In the geomorphological context, the results indicate that bridges located in mountainous areas are more frequently associated with medium to large landslide magnitude classes, whereas bridges situated in flat areas are predominantly affected by low to medium magnitude events. The results show that the majority of the evaluated bridges (83%) fall within the very small Pm category (M > 10²), indicating a generally low level of landslide-related exposure. Only 7% are classified as large, 7% as medium, and 3% as extreme large (M > 10⁶), highligh ting that only a small fraction of structures is potentially at higher risk. These areas pose a potential threat to man-made structures, regardless of the current activity of individual landslides. This refined interpretation highlights landslide magnitude as a key controlling factor, particularly in steep and geologically complex terrains, while confirming that using an empirical formula for volume estimation, even approximately, ensures the workflow remains feasible and applicable at a national scale. 3.5. Landslide velocity (P v ) assessment Landslide velocity ( P v ) was calculated by analyzing ground motion data from the European Ground Motion Service ( EGMS ) over the period 2019-2023. Sentinel-1 satellite radar data were processed using Persistent Scatterer Interferometry ( PS-InSAR ) in ascending (S-N) and descending (N-S) orbits. Velocity values from descending and ascending tracks ranged from -14.0 to 19.4 mm/year and from -18.7 to 10.1 mm/year, respectively (Fig 4).

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Fig. 4. (a) Landslide velocity ( P v ) assessment map; (b) Landslide velocity ( P v ) assessment graph.

The maximum velocity value within a 300m buffer zone around each bridge was considered as the Landslide Velocity ( P v ) parameter and classified according to the national guidelines MIMS (2022). Negative velocities indicate motion away from the satellite, generally associated with slope instability or subsidence, while positive velocities represent motion towards the satellite. The results reveal the spatial distribution of deformation areas, with clusters of higher velocities in geologically susceptible zones. Most of the examined bridges are classified under the 'very slow' P v category, signifying a generally low level of displacement activity. The results indicate that bridges having slow, moderate, and rapid velocity classes are predominantly located in mountainous areas (>10°), whereas those situated in flat areas (0–10°) are mostly associated with negligible or very low deformation rates. Nevertheless, few structures exhibit slow, moderate, or even rapid movement patterns despite their location in less steep terrain. This underscores the variations in slope behavior throughout the research area, highlighting the necessity of site-specific analysis. 4. Results of bridge Susceptibility and discussion The susceptibility class was calculated using point-based system that combines three primary parameters and subsequently grouping the total scores into five susceptibility categories: Low (5-7), Medium-Low (8-11), Medium