Development of fragility curves for highways in areas with liquefaction-induced lateral spreading potential and application to the D100 highway in Küçükçekmece Avcılar

The resilience of infrastructure, particularly transportation networks, is of vital importance in terms of disaster preparedness, emergency response, and recovery processes. Given the critical role of highways in post-disaster logistics and emergency interventions, maintaining their functionality following seismic events is essential. Resilience is defined based on factors such as vulnerability and recovery time, with the focus of this study being on reducing vulnerability. In this context, identifying the weak points of highway systems before an earthquake is crucial for implementing preventive measures to mitigate potential damage. In the scope of this thesis, the vulnerability of highways to liquefaction-induced lateral spreading displacements was investigated using two distinct approaches: fragility curves and an index-based method.For the fragility curves, a finite element model was first calibrated using data from the Sapanca Vakıf Hotel site, where lateral spreading was observed during the 1999 Kocaeli Earthquake. Subsequently, a series of nonlinear dynamic analyses were performed on the calibrated finite element model to develop fragility curves based on the exceedance probabilities of selected damage states at varying levels of intensity measure as PGA. For the index-based vulnerability assessment, parameters affecting roadway damage observed in past earthquakes were weighted using the Analytic Hierarchy Process. Both the developed fragility curves and the index-based vulnerability assessment were validated using field observations of lateral spreading damage from the February 6, 2023 Kahramanmaraş Earthquakes in Adıyaman/Gölbaşı and Hatay/Demirköprü districts. In Adıyaman-Gölbaşı, in-situ geotechnical field investigations were conducted in the area affected by lateral spreading. For Hatay-Demirköprü, data was obtained from the literature. In both cases, the observed damage levels were found to be consistent with those estimated by the fragility curves and the index-based method. An application was carried out on the Küçükçekmece–Avcılar section of the D100 highway in Istanbul using the validated methods. In this way, the resilience of this highway in terms of maintaining its functionality during the anticipated Istanbul earthquake was evaluated, both with respect to ultimate use and emergency post-disaster use. As a result, this study has made original contributions to the literature on the seismic resilience of highways and proposed a decision-support tool aimed at enhancing infrastructure safety in seismic regions.