Browsing by Author "Tuna, Şahin Çağlar"

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Effect of Spatial Variability of Soil Properties on Liquefaction Behaviour – a Probabilistic Approach
(Springer, 2026) Tuna, Şahin Çağlar
This study presents a high-resolution, site-specific probabilistic framework for assessing soil liquefaction hazard by explicitly modeling subsurface spatial variability and seismic hazard. Gaussian Random Field (GRF) modeling and Monte Carlo simulation were used to generate 1,000 realizations of cone tip resistance (qc) and sleeve friction (fs), calibrated from 39 Cone Penetration Tests (CPTs). Liquefaction triggering was evaluated using the CSR-CRR procedure, and the depth-integrated Liquefaction Potential Index (LPI) was computed for each realization. Monte Carlo simulations were performed under a fixed seismic demand (PGA = 0.174 g) to isolate the effects of soil spatial variability, while seismic hazard uncertainty was subsequently incorporated by convolving site-specific fragility functions with PGA-based hazard curves TBDY ( Turkish Building Earthquake Code, 2018). Logistic regression produced site-calibrated fragility relationships between LPI and the probability of liquefaction (P[Liq]), enabling multi-threshold evaluations for LPI > 15, 25, and 45. The risk density peaked near PGA approximate to 0.18 g, indicating that moderate ground motions dominate liquefaction risk. The annual probability of exceeding LPI > 15 was approximately 1.92 x 10(-3) (approximate to 0.192%/yr; similar to 1 in 521 years), indicating a non-negligible annual liquefaction hazard. This framework enhances realism in liquefaction risk estimation and provides actionable guidance for performance-based geotechnical design, seismic mitigation, and hazard-informed infrastructure planning in regions susceptible to soil liquefaction.
Citation - WoS: 2
Citation - Scopus: 2
Probabilistic assessment of soil liquefaction-induced failures during the 2023 Kahramanmaraş earthquakes in Türkiye: A case study from Iskenderun city
(Elsevier Ltd, 2025) Şahin Çaǧlar Tuna; Tuna, Şahin Çağlar
The February 6 2023 Kahramanmaraş earthquakes and their aftershocks caused devastating destruction across Türkiye and Syria. Widespread liquefaction-induced damage—particularly in regions such as Iskenderun Adıyaman-Gölbaşı Hatay-Dörtyol and Reyhanlı—was reported along with general structural damage throughout the affected areas. This study addresses the critical issue of soil liquefaction within a probabilistic earthquake–soil–structure interaction framework and provides a comprehensive assessment of its impacts. An empirical methodology is proposed for estimating liquefaction-induced settlements near buildings by integrating post-earthquake reconnaissance observations with analytical results within a Performance-Based Design (PBD) framework. The analysis focuses on three regions within the Iskenderun district which were selected based on observed evidence of liquefaction and underlying geotechnical characteristics. Geotechnical investigation reports and recorded ground motion data were employed to evaluate the influence of local soil conditions. Site effects were evaluated using one-dimensional site response analyses which allowed for the simulation of ground motion amplification. The resulting surface acceleration time histories served as the basis for the damage assessment. To quantify liquefaction susceptibility a data-driven classification of the Liquefaction Potential Index (LPI) was conducted using K-Means clustering facilitating the derivation of optimized thresholds for damage severity. Based on this classification empirical fragility functions were developed to relate the Liquefaction Potential Index (LPI) to the Damage Severity Index (DSI) enabling the estimation of exceedance probabilities for different damage states. The findings highlight the importance of probabilistic fragility modeling in enhancing seismic hazard mitigation strategies and informing risk-based engineering decisions. © 2025 Elsevier B.V. All rights reserved.
Soil-Structure Interaction Analysis of Shallow Rectangular Tunnels Based on the Performance-Based Design Concepts
(Springer, 2025) Şahin Çaǧlar Tuna; Selim Altun; Altun, Selim; Tuna, Şahin Çağlar
This study analyzed seismic responses of shallow rectangular tunnels within the framework of soil-structure-soil interaction. The idealized soil profile and properties were derived from site-specific investigation reports. Racking curves typically used in design were reevaluated to reflect local soil conditions nonlinear soil behavior and seismic influences. Results differed significantly from traditional literature findings emphasizing the importance of localized factors. Finite element methods enabled nonlinear soil parameter modeling and time-history analysis of soil-structure systems. Literature reviews and case studies identified potential damage states with discrete damage levels. The findings quantified probabilities of these damage states and established recurrence relationships for system damages. Fragility curve analyses widely employed in structural engineering were used to develop graphical representations of damage probabilities. This study’s outcomes provide insights into the seismic behavior of tunnels under localized conditions and enhance reliability in geotechnical and structural engineering designs. © 2025 Elsevier B.V. All rights reserved.