Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
8 results
Search Results
Article AI-Supported Seismic Performance Evaluation of Structures: Challenges, Gaps, and Future Directions at Early Design Stages(Elsevier Sci Ltd, 2026) Ak, Fatma; Ekici, Berk; Demir, UgurThis study reviews 91 journal articles that intersect with earthquake-resistant building design and artificial intelligence (AI)- based modeling, utilizing machine learning, deep learning, and metaheuristic optimization algorithms. Previous reviews on AI applications have examined engineering problems without considering the impact of architectural design parameters and structural irregularities on seismic performance. This review discusses the role of AI in integrating architectural design variables and seismic performance objectives, highlighting challenges, gaps, and future directions in the early design phase. The reviewed articles demonstrate that AI is successful in addressing seismic performance objectives; however, a holistic framework for assessing architectural and structural variables has not been presented. The review highlights key findings, gaps, and future directions for those involved in earthquake-resistant building design utilizing AI.Article Damage Assessment of Structures Following the February 6, 2023 Kahramanmaraş Earthquakes: A Dataset-Based Case Study in Gaziantep, Türkiye(Springer Heidelberg, 2025) Atasever, Kurtulus; Aydogdu, Hasan Huseyin; Narlitepe, Furkan; Goksu, Caglar; Demir, Ugur; Demir, Cem; Ilki, AlperFollowing the 2023 Kahramanmara & scedil; Earthquakes (Mw 7.7 and 7.6) that struck T & uuml;rkiye on February 6, 2023, the Ministry of Environment, Urbanization, and Climate Change (MoEUCC) initiated a large-scale post-earthquake damage assessment campaign, targeting more than 2,3 million structures within the affected region. A comprehensive field survey was carried out in and around Gaziantep, one of the most severely affected cities. The authors assessed more than 1700 structures representing a wide range of occupancy types, including residential, educational, healthcare, religious, administrative, industrial, and lodging structures. In this paper, the methodological process of post-earthquake data collection in and around Gaziantep is presented, together with the data on the distribution of damage with respect to construction period, number of stories, and building occupancy type, to ensure a complete understanding of the extent and characteristics of structural damage. The damage assessment employed two data sources: (i) the data gathered through the authors' newly developed, novel damage-assessment software, presented here for the first time, and (ii) the official post-earthquake damage database of the MoEUCC. A further novelty of this study is the presentation of the largest dataset to date for the investigated earthquake doublet, encompassing approximately 1700 buildings. Additionally, the relationship between damage states, peak ground accelerations, and fault distances is thoroughly investigated. The detailed earthquake-hit site investigations revealed that the examined structures displayed structural inadequacies akin to those witnessed in previous seismic events, with a notable focus on the arrangement of the structural system, the quality of construction materials and reinforcement detailing.Article Repair and Strengthening of Fire Damaged Concrete Cylinders Using FRP Confinement: Tests and Analytical Modelling(Elsevier Science inc, 2025) Demir, Ugur; Ilki, AlperThis study examines the effects of fiber-reinforced polymer (FRP) repair and strengthening on the axial stress-strain behavior of concrete columns after exposure to realistic fires. A total of 30 plain concrete cylinders, each measuring 150 x 300 mm, were cast for this investigation. Of these, three specimens were kept as reference at ambient temperature, while the remaining were exposed to ISO-834 standard fire for durations of 30, 60 or 90 min, with nine specimens in each duration group. After natural cooling, the heated specimens were categorized into three groups: i) three were left unconfined, ii) three were repaired and strengthened using two layers of carbon FRP sheets, and iii) three were repaired and strengthened with four layers of carbon FRP sheets. This study employs realistic ISO 834 fire scenarios and investigates CFRP confinement with up to four layers, addressing high confinement demands beyond current literature. The results showed that transverse confinement provided by carbon FRP sheets significantly improved axial strength and deformability for all specimens, while it did not fully restore the axial stiffness achieved before fire exposure. The effectiveness of FRP confinement increased with longer fire exposure durations. Additionally, two analytical models proposed previously for predicting the axial strength and ultimate strain of FRP confined fire-damaged concrete were evaluated in terms of their accuracy. The accuracy of the predictions was reduced with an increase in exposure temperatures for both models. Therefore, a new model is proposed within the scope of study, which shows good agreement with the novel test results.Article A Comprehensive Database and a New Model for the Axial Response of Heat-Damaged Concrete Before and After FRP Confinement(Springer, 2025) Akdag, Nefise; Demir, UgurIn this study, a total of 330 concrete specimens, compiled from existing experimental data, are systematically reviewed to assess their post-fire axial stress-strain behavior before and after circumferential confinement with fiber-reinforced polymers (FRPs). The selection criteria for the database are as follows: (i) studies had to be published in English, (ii) both lateral and axial ultimate strains must have been measured, (iii) the use of additional strengthening materials in combination with FRPs was excluded, (iv) only plain concrete specimens were considered, and (v) specimen dimensions and instrumentation details had to be explicitly reported. The dataset is structured to include heating/cooling and curing conditions, specimen properties, and FRP characteristics. Subsequently, the predictive accuracy of available models for post-fire axial strength and ultimate strain of concrete members, both before and after FRP confinement, is evaluated. The results based on the reviewed comprehensive database indicate that these models are inadequate in capturing the observed behavior in the experiments. As such, a new analytical model is developed based on the compiled dataset. The proposed model demonstrated reliable predictive performance in terms of post-fire axial response of concrete before and after FRP confinement while remaining user-friendly for practical engineering applications. This is done such that universal design guidelines on the behavior of heat-damaged concrete strengthened by FRP composites can be reliably formulated.Article Citation - WoS: 3Citation - Scopus: 3A Novel Hybrid Thin Jacketing Method for Seismic Retrofitting of Substandard Reinforced Concrete Columns(Elsevier Ltd, 2025) Narlitepe, Furkan; Kian, Nima; Demir, Ugur; Demir, Cem; Ilki, AlperThis paper introduces a novel hybrid thin jacketing method for seismic strengthening of substandard reinforced concrete (RC) columns for which structural repair mortar along with carbon fiber reinforced polymer (CFRP) and longitudinal steel bars are utilized. The method involves three application phases comprising a) removing the cover concrete, b) re-forming the cover concrete with structural repair mortar just after installing extra longitudinal steel bars c) transverse wrapping of CFRP sheets. The effect of using different types of structural repair mortar and its application process are other test parameters taken into account in this study. To evaluate the efficacy of the proposed method, a comprehensive experimental program was conducted, consisting of six largescale RC column specimens with square and rectangular cross-sections. For all of the specimens tested under a simultaneous constant axial load and reversed cyclic lateral loading, three main properties representing existing substandard RC columns such as a) insufficient transverse reinforcement, b) high axial load ratio (0.75) and, c) relatively high shear force corresponding to moment capacity to shear capacity ratios between 0.60 and 0.80, were considered. The responses of specimens were specified in terms of the lateral load-displacement curves, stiffness variation, ductility ratios, damage progression, and energy dissipation. The experimental results demonstrated that in case the retrofitting method is properly applied, the strengthened columns exhibit satisfactory performance in terms of strength and ductility with a remarkable improvement with respect to the substandard columns. Furthermore, a numerical study was conducted to validate the experimental results by using the OpenSees framework.Article Citation - WoS: 2Citation - Scopus: 2Experimental Integration of Stone Topologies To the Simplified Micro-Modeling for the Seismic Response of Masonry Walls: a Novel Insight(Springer Heidelberg, 2025) Demir, UgurThis study aims to explore the impact of stone typologies on the in-plane seismic behavior of stone masonry buildings. The present study aims to quantify the strength and deformability parameters such as lateral load capacity, ductility, energy dissipation capacity and stiffness degradation of frequently used sandstone and limestone masonry, which will intentionally contribute to the core body of knowledge on their original structural design, seismic safety evaluation and intervention design. The innovative aspect of this research lies in the holistic methodology that integrates field surveys to classify local stone masonry units, experimental characterization of the chemical and mechanical properties of these units to capture variability, and finite element modeling of the in-plane cyclic behavior of stone masonry walls using experimental data. A novel simplified micro-modeling approach is implemented within a standard finite element software, eliminating the need for user-defined subroutines. This approach significantly reduces computational efforts compared to conventional methods, making it particularly suitable for analyzing large-scale stone masonry structures. The study investigates the impact of chemical composition (sandstone or limestone), applied axial stress (0.25 MPa, 0.50 MPa, or 1 MPa), and wall aspect ratios (height-to-length ratios of 1.0 or 1.5) on wall performance. The modeling approach is validated against experimental results from the literature, demonstrating good agreement. Finally, the study assesses wall performance in terms of deformation limits in current seismic codes. The findings provide critical insights for developing innovative design strategies to enhance the structural integrity of stone masonry walls and improve the seismic assessment of existing structures.Article Citation - WoS: 3Citation - Scopus: 3Seismic Testing and Modeling of Full-Scale Substandard Rc Columns Retrofitted With Sprayed Gfrm With and Without Basalt Mesh Under High Axial Compression and Shear Demand(Asce-Amer Soc Civil Engineers, 2025) Kian, Nima; Demir, Ugur; Ates, Ali Osman; Celik, Oguz C.; Ilki, AlperThis study presents the experimental and analytical hysteretic behaviors of eight full-scale RC square and rectangular columns. The columns were designed to have different shear spans that represent: (1) a column that complies with the Turkish Government Ministry of Reconstruction and Resettlement's ( 1975) seismic design code, Turkish Seismic Design Code (TSDC); (2) a substandard column; and (3) two sprayed glass fiber-reinforced mortar (GFRM)-retrofitted counterparts of the substandard column with and without basalt mesh. The substandard columns were designed to be subjected to relatively high shear ratios (i.e., the ratio of the shear force that corresponds to the moment capacity to shear strength of the cross section) up to 0.85 and with a high axial load-to-capacity ratio of 0.75. All columns were tested under constant axial load and reversed cyclic lateral displacement excursions. The results revealed that the columns that complied with the TSDC showed satisfactory behavior for seismic performance, and the performance of the substandard columns was extremely poor. However, the hysteretic performance of the substandard columns that were subjected to high axial stress and shear significantly improved after the proposed retrofitting. Finally, a numerical model was developed in OpenSees to reproduce the hysteresis curves of the specimens. The slip of the longitudinal bars at the column-foundation interface, strain penetration into the foundation, and buckling of the longitudinal bars in compression were accounted for in the modeling. The results are in good agreement with the experimental hysteresis curves. The performance levels of the columns are further specified, and the predictions of the current seismic codes were analyzed: (1) the European Committee for Standardization's 2005 code, Eurocode 8: Design of structures for earthquake resistance; Parts 1-3: Strengthening and repair of buildings (EC8-3); and (2) the Turkish Government Ministry of Interior Disaster and Emergency Management Authority's 2018 code, Turkish Building Earthquake Code (TBEC). The TBEC provided more accurate estimates of plastic rotation capacities for substandard specimens. In contrast, EC8-3 overestimated the plastic rotation capacity when shear stresses were relatively high due to lower shear span-to-depth ratios (a/d).Article Impact of High Axial Stress on Seismic Behavior of Substandard Reinforced Concrete Columns(Elsevier Science inc, 2025) Gundogan, Safiye; Demir, Ugur; Turan, O. Tugrul; Ilki, AlperThe seismic performance of reinforced concrete (RC) buildings, particularly those constructed without adequate seismic detailing, remains a critical concern in earthquake-prone regions worldwide. Many of these buildings, often referred to as substandard RC structures, were built before modern seismic codes were established and are characterized by poor material quality and inadequate construction practices. The Southern T & uuml;rkiye earthquakes on 6 February 2023 underscored the urgent need to better understand the seismic behavior of these substandard structures, which frequently fail to meet modern design standards and are prone to damage or collapse. Substandard RC columns, characterized by low concrete strength and inadequate transverse reinforcement, are susceptible to severe seismic damage, increasing the risk of collapse and life loss. While numerous studies have experimentally examined the seismic behavior of RC columns under low to moderate axial load to capacity ratios (typically below 0.30), these conditions do not accurately reflect the reality of many existing substandard columns that are frequently subjected to higher axial compression stresses. This study addresses this critical gap by presenting the first experimental data on the seismic behavior of full-scale, substandard RC columns under high axial load ratios (0.30-0.80). The analysis focused on lateral load-displacement relationships, ductility, plastic hinge length, stiffness, energy dissipation capacity, and residual displacements. Increases in axial load led to more brittle failure modes, reduced displacement ductility and an extended plastic hinging zone. High axial loads also caused accelerated stiffness degradation, reduced cumulative energy dissipation, and progressive residual deformations. Analytical models overestimated deformation capacity, making them unreliable for substandard RC columns under high axial stress. Additionally, predictions using plastic hinge length formulas underestimated the values at high axial loads. The study also evaluated the performance of widely used concrete confinement models in predicting the moment-curvature responses and corresponding ductility for substandard RC columns with low compressive strength and subjected to high axial stress. These findings underscore the critical need for refined modelling approaches and assessment methodologies to improve the seismic evaluation of substandard existing buildings.