Demir, Uğur
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Demir, Ugur
Demir, U.
Demir, U
Demir, U.
Demir, U
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ugurdemir@iyte.edu.tr
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02.02. Department of Architecture
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Current Staff
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3GOOD HEALTH AND WELL-BEING
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4QUALITY EDUCATION
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8DECENT WORK AND ECONOMIC GROWTH
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
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10REDUCED INEQUALITIES
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11SUSTAINABLE CITIES AND COMMUNITIES
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Documents
27
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119
h-index
7
Documents
17
Citations
96
Scholarly Output
21
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10
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4753/1978
Supervised MSc Theses
4
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0
WoS Citation Count
19
Scopus Citation Count
28
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WoS Citations per Publication
0.90
Scopus Citations per Publication
1.33
Open Access Source
5
Supervised Theses
4
| Journal | Count |
|---|---|
| Engineering Structures | 2 |
| Structures | 2 |
| Arabian Journal for Science and Engineering | 2 |
| Lecture Notes in Civil Engineering | 2 |
| Turkish Journal of Civil Engineering | 1 |
Current Page: 1 / 2
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21 results
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Now showing 1 - 10 of 21
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.Master Thesis An Investigation of Design Parameters Influencing Post-Fire Irreparable Structural Damage Limit(01. Izmir Institute of Technology, 2024) Demir, Uğur; Çelik, Elif Naz; Demir, UğurSon yıllarda, yangın durumunda oluşan deformasyonların sınırlandırılması, sonraki dönemde oluşabilecek onarılamaz hasarları önlemek amacıyla inşaat sektörü için zorunlu bir hale gelmiştir. Bu amaç doğrultusunda, bu çalışma, yangın etkisi altında betonarme yapısal sistemlerin kullanılabilirlik durumunu etkileyen kritik faktörleri detaylı bir şekilde incelemektedir. Araştırma, betonarme kirişlerin sehimlerinin, yangına maruz kalan kolonların yük taşıma kapasiteleri ve birleşik termal ve mekanik yükleme altındaki kolon öteleme oranlarının doğrusal olmayan sonlu eleman modellemeleri temelinde gerçekleştirilmiştir. Yapısal sistemler ve malzemelerin kullanılabilirlik sınırları önemli ölçüde göz önünde bulundurulmuştur. Yangın olayını simüle etmek için, kompartman alanı, havalandırma açıklıkları ve termal atalet gibi değişken özelliklere sahip parametrik bir yangın eğrisi kullanılmıştır. Hesaplama sürecini daha uygun hale getirmek amacıyla parametrik eğriler üretebilen bir yazılım çalışmaya dahil edilmiştir. Mekanik davranış, betonarme (RC) kirişin maksimum taşıma kapasitesi altında incelenmiştir. Mevcut yönetmeliklerde belirtilen kullanılabilirlik sınır durumu için verilen sehim sınırları ve öteleme oranları, sayısal bulgularla karşılaştırılmış; havalandırma koşullarının sehim davranışı üzerindeki etkisi buna bağlı olarak tartışılmıştır. Çalışma, yangından zarar görmüş RC elemanları ile belirli bir yangın senaryosu arasında bir ilişki kurulmasının mümkün olabileceğini ve bunun, tasarımda performans tabanlı yapısal yangın güvenliğinin ilerlemesine katkıda bulunabileceğini ortaya koymaktadır. Simülasyonların, yapısal yangın güvenliğinin sağlanmasında önemli bir bileşen olan mimarlara, binaların ilk tasarım aşamasında açıklıkların sayısını ve boyutlarını optimize etme, malzeme seçimi yapma ve kapalı alanların boyutlandırılması konusunda rehberlik etme potansiyeli bulunmaktadır.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: 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 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.Conference Object Citation - WoS: 1Citation - Scopus: 2Seismic Performance of Substandard Rc Columns Retrofitted With Sprayed Gfrm(Springer, 2022) Kian, Nima; Demir, Uğur; Demir, Cem; Maraşlı, Muhammed; İlki, AlperThere is a myriad amount of substandard reinforced concrete (RC) buildings in developing countries that do not comply with the requirements and instructions of the current building design codes. In particular, columns in these substandard buildings demonstrate unsatisfactory and undesired behavior against lateral loads, mainly due to low concrete compressive strength and poor reinforcement detailing. The problem is exacerbated when the axial load ratio (ratio of applied axial load to the axial load capacity) and/or the shear ratio (ratio of shear force corresponding to moment capacity (Ve) to the shear capacity (Vr)) is/are high, leading to brittle failure modes. In this study, three full-scale substandard RC columns subjected to high axial load ratio of 0.75 were tested under constant axial load combined with reversed cyclic lateral displacements. Shear ratio (Ve/Vr) of the substandard columns were 0.75 and 0.82 according to ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and (Turkish Building Earthquake Code (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), respectively. According to the TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), columns had a high Ve/(fctmbd) ratio of 1.12, where, fctm, b, and d are the direct tensile strength of concrete, width of the cross-section, and effective depth of the section. The ratio of transverse reinforcement to minimum required transverse reinforcement according to the ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey) was 0.19 and 0.77, respectively. Two of the columns were retrofitted with an innovative, cost-effective, and easily-applicable strengthening method, through external jacketing with sprayed glass fiber reinforced mortar (GFRM) of different characteristics. The remaining column was tested as the reference specimen to evaluate the efficiency of the strengthening method. The test results demonstrated the extremely poor performance of the reference substandard column as well as the remarkable lateral load capacity and ductility improvement provided by the adopted novel strengthening approach.Article Citation - WoS: 10Citation - Scopus: 14Out-Of Seismic Performance of Bed-Joint Reinforced Autoclaved Aerated Concrete (aac) Infill Walls Damaged Under Cyclic In-Plane Displacement Reversals(Elsevier, 2023) Halıcı, Ömer Faruk; Demir, Uğur; Zabbar, Yassin; İlki, AlperThe infill walls made of Autoclaved Aerated Concrete (AAC), which is a lightweight, fire resistant and energy efficient material, provide effective insulation solutions for building types of structures and becoming more and more popular in earthquake prone regions. Although the number of experimental tests examining the seismic response of clay brick infills is extensive, the amount of prior research on infill walls built of AAC blocks is rather limited. Past research revealed that the use of bed-joint reinforcement is one of the promising solutions to improve the global seismic response of masonry walls by enhancing strength and displacement capacity. In this study, the out-of-plane (OOP) seismic performance of AAC infill walls with flat-truss and innovative cord-type bed-joint reinforcement is experimentally evaluated. Also, consideration is given to the prior in-plane (IP) damage, which was found to degrade the seismic performance of infills in OOP direction. For this purpose, three IP and four OOP, in total, seven experimental tests were performed on four full-scale AAC infill wall specimens. The test parameters were selected in such a way as to make it possible to parametrically compare the OOP performance of AAC infills with flat-truss and cord-type bed-joint reinforcements with unreinforced AAC infill walls, together with the effect of prior IP damage on the OOP response of unreinforced AAC infill walls. It was found that the use of innovative cord-type bed-joint reinforcement improved the OOP strength to a similar extent to what was obtained from the truss-type reinforced specimen. In terms of ultimate displacement and energy dissipation capacity enhancement, the specimen with cord-type reinforcement performed better. In addition, the damages formed due to IP cyclic displacement reversals up to 0.005 drift ratio, which is defined as the drift limit for buildings with brittle infill walls in certain design codes, resulted in a significant reduction in the OOP strength and stiffness properties of AAC infills. The theoretical OOP strength calculations were found to provide unconservative strength values for the IP-damaged specimens.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 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 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.
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