Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Book Part Influence of High Sustained Axial Stresses on the Seismic Behavior of Full-Scale Substandard Reinforced Concrete Columns(CRC Press, 2025) Gundogan, S.; Demir, U.; Turan, O.T.; Ilki, A.Reinforced concrete (RC) columns are critical structural components that play a decisive role in the seismic performance of buildings. However, the combined effects of long-term sustained axial loads and seismic loading on these columns remain a pressing concern. In particular, design and construction deficiencies, coupled with material deterioration, often result in substandard RC columns experiencing long term axial stresses that far exceed typical service levels. These elevated stress conditions can lead to significant structural vulnerabilities, manifesting as collapses under seismic actions or even under gravity loads alone. Within this context, this study aims to investigate the impact of such high sustained axial stresses on the response of substandard reinforced concrete columns prior to be subjected to reversed cyclic lateral loading simulating seismic actions. For this purpose, two full-scale columns were tested under the combined actions of axial load and reversed cyclic lateral displacements. One of two columns were tested after it was exposed to a sustained axial load of 825 kN, corresponding to 70% of axial load capacity (fbh) for a duration of six months, while the other column was tested as the reference specimen right after it was subjected to same level of axial load. Comprehensive instrumentation during testing and detailed creep analysis under long-term applied axial loads were conducted to evaluate the response of the columns. The findings highlight the significant impact of long-term high axial stress on the seismic performance of substandard RC columns. © 2025 selection and editorial matter, Alphose Zingoni; individual chapters, the contributors. All rights reserved.Book Part 25 Years of FRP Research at Istanbul Technical University(CRC Press, 2025) Ilki, A.; Sari, B.; Goksu, C.; Demir, C.; Demir, U.; Töre, E.The application of fiber-reinforced polymer (FRP) composites for structural strengthening and seismic retrofitting has significantly advanced in recent decades. This study presents a com-prehensive review of FRP research conducted at Istanbul Technical University (ITU) in the last 25 years, which has closely aligned with global developments in the field. The research at ITU has focused parti-cularly on addressing the substandard characteristics prevalent in Türkiye's building stock. Investigations have spanned a wide range of specimens, from small-scale concrete prisms to full-scale three-dimensional reinforced concrete (RC) buildings. Key focus areas have included FRP applications for ductility enhancement, flexural strengthening and seismic retrofitting of structural members. Various FRP mate-rials have been examined, including aramid, glass, carbon, basalt and PET fibers. Multiple application techniques have been explored, ranging from externally bonded reinforcement to textile reinforced sprayed mortar. The findings from these extensive studies have consistently demonstrated the efficacy of FRP composites in enhancing the structural performance and seismic resilience of substandard buildings. This body of research has made significant contributions to the development of practical retrofit solutions tailored to the specific challenges posed by Türkiye's existing building stock and has broader implications for seismic risk mitigation in countries with similar construction practices. © 2025 selection and editorial matter, Alphose Zingoni; individual chapters, the contributors. All rights reserved.Conference Object Strengthening of Reinforced Concrete Columns Using Recycled Polyethylene Terephthalate Fibers: A Preliminary Numerical Study(fib. The International Federation for Structural Concrete, 2025) Dalgic, K.D.; Gozun, U.; Simsek, B.; Sencar, I.; Ispir, M.; Ilki, A.Strengthening of reinforced concrete (RC) columns, which have inadequate capacities of deformation and axial/lateral load, using carbon fiber reinforced polymers (CFRP) has become widespread. However, concerns about cost, energy sustainability and environmental impact have led to increased interest in alternative fibers, such as recycled polyethylene terephthalate (PET) fibers, instead of high-tech, carbon-intensive materials. This study presents preliminary numerical analyses on the use of PET fibers recycled from tire industry waste in Türkiye to strengthen substandard RC columns. The numerical analyses of the column models were performed under axial and horizontal loads. The results show that even small amounts of PET-FRP fibers can significantly improve both lateral load and deformation capacities of RC column, indicating the development of strengthening strategies for upcoming column tests. Based on the results of numerical studies, an experimental program for quasistatic testing of substandard RC columns has been planned. © 2025 Elsevier B.V., All rights reserved.Conference Object Citation - Scopus: 1Observed Performance of a RC Wall-Frame Building During the February 2023 Turkey Earthquake and Performance Improvement Using FRPs(International Institute for FRP in Construction (IIFC), 2023) Tura, C.; Sahinkaya, Y.; Güllü, M.F.; Demir, U.; Orakcal, K.; Ilki, A.In this study, results of nonlinear response history analysis are presented for an existing RC wall-frame building, which has suffered collapse-level damage during the devastating February 2023 Kahramanmaras earthquakes. Performance analysis results for two building configurations are compared; first for the existing building configuration generated upon on-site observations, and second, for a hypothetical configuration in which the structural walls and columns are retroffited using externally-bonded FRP sheets. Analysis results reveal that in its existing configuration, mostly due to detailing deficiencies, a collapse-level performance was not unexpected; whereas FRP strengthening of the building would have resulted in collapse-prevention performance. © CICE 2023 - 11th International Conference on FRP Composites in Civil Engineering. All rights reserved.Article Citation - WoS: 61Citation - Scopus: 60Performance of Structures in İzmir After the Samos Island Earthquake(Springer, 2022) Yakut, A.; Sucuoǧlu, H.; Binici, B.; Canbay, E.; Dönmez, C.; Ilki, A.; Ay, B.Ö.The October 30, 2020 Earthquake caused unexpectedly significant damage in İzmir considering its distance to the city. This paper evaluates the recorded ground motions, summarizes the performance of structures affected from the earthquake with emphasis on the reasons of damage. A detailed damage assessment was carried out by the Earthquake Engineering Research Center of Middle East Technical University to compile data on the damage of RC and masonry buildings. It was observed that majority of the damage was concentrated in the Bayraklı district due to its peculiar soil properties where many 7–10 story mid-rise RC buildings suffered heavy damage and collapse. The level of amplified ground motions combined with deficiencies of apparently non-code compliant buildings exacerbated the damage. The main reasons of damage were mainly attributed to the presence of soft stories, lack of proper detailing, poor construction quality, presence of heavy overhangs, and hence significant lack of code-compliance in essence. The influence of infill walls on seismic performance of deficient and inadequate buildings was clearly seen in this earthquake. This paper also discusses seismic code requirements in effect and their influence on the observed building performance. The recorded ground motions were compared with the code spectra to evaluate the performance of the buildings. The code response spectra were found to be well above the recorded ground motion spectra at the sites where significant damage was observed. © 2021, The Author(s), under exclusive licence to Springer Nature B.V.