Loli M., Chatzidaki A., Vamvatsikos D., Gazetas G. (2021). Seismic vulnerability of motorway bridge on active landside. Proceedings of the 17th World Conference on Earthquake Engineering (17WCEE), Sendai, Japan
Abstract | The western section of Egnatia Odos motorway in Greece runs through a challenging mountainous terrain where geohazards are exacerbated by moderate seismicity. Located a few kilometers east of the town of Metsovo, the twin girder bridges of the Panagia interchange have their central piers founded on an active landslide. Being part of a research project that aims to develop a tool for rapid inspection and assessment of the motorway, this study presents a thorough seismic vulnerability analysis of the hybrid caisson–pile group foundation system that supports the most critical piers of the interchange. This foundation system has been designated as a slope stabilizing measure, in addition to carrying the loads transmitted by the bridge superstructure. Numerical modelling with nonlinear 3D finite elements has been employed, together with site-specific hazard-consistent selection of ground motion records. A hybrid numerical approach has been developed using segregated models of varying refinement with rational approximation of interactions between the nonlinear response of soil, the movement of the slope, the kinematic distress imposed upon the foundation and the inertial loads from the vibration of the superstructure. The method estimates pile performance under large-scale, dynamic landslide action with sufficient engineering accuracy for cases where slope actions dominate the response. The softening behavior of the sliding surface is calibrated versus monitored slope displacements. The effect of groundwater recharge after heavy rainfall is incorporated in the vulnerability analysis in a simplified manner, using different scenarios for water table elevation. Focusing on the performance of the foundations, damage is described in terms of their permanent displacements and curvatures. Results indicate that a range of excitations with an exceedance
probability of 2% in 50 years are capable of inflicting substantial permanent pile damage, even complete failure, if combined with a fully saturated soil condition. The computed residual foundation displacements can serve as input for a detailed structural model simulating the performance of the superstructure for estimating the bridge vulnerability.