Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 3Citation - Scopus: 5Helenistik Kulelerde Yanal Yüke İlişkin Düzlem İçi ve Düzlem Dışı Duvar Davranışının Duvar Profilleri ve Açıklık Düzenlerine Bağlı Olarak İncelenmesi(Gazi Üniversitesi, 2020) Gençer, Funda; Turan, Mine; Aktaş, EnginDry masonry wall profiles constructed without using bonding material between blocks are encountered in different building types dated to Greek, Hellenistic and Roman periods. Depending on development of earthquake experiences, dry masonry wall profiles vary in terms of wall thickness, number of layers, relationship of layers and size, form, organization and relationship of blocks. In this study, the construction details increasing the structural strength in watch towers constructed in Hellenistic Period are aimed to be determined. This study is limited with investigation of effect of wall profiles and opening organizations on in-plane and out-of-plane wall behaviors under lateral loading. Primarily, wall profiles and opening types of dry masonry towers in ancient Caria, Pamphylia and Cilicia regions, that have not lost authenticity and integrity or had information about their authentic form, were documented. By using gathered data, hypothetic towers with different wall profiles and opening types are designed. To determine in-plane and out-of-plane wall behavior of hypothetic towers, simulation of quasi-static tilt analysis based on equilibrium were carried out, and form changes at walls and collapse angles of towers were identified. Wall profile and opening properties effecting on structural strength under lateral loading were determinedd.Article Citation - Scopus: 4Betonarme Çerçeve Yapıların Olasılıklı Sismik Analizi(Gazi Üniversitesi, 2006) Korkmaz, Armağan; Aktaş, EnginBetonarme çerçeve yapıların sismik davranışlarının belirlenmesinde, analizlere olasılıklı ifadelerin dahil edilmesi, sismik davranışın daha gerçekçi tanımlanmasına yardımıcı olacaktır. Çalışmada betonarme çerçeve yapıların olasılıklı sismik analizlerinin gerçekleştirilmesi amaçlanmış, bu amaçla örnek betonarme çerçeve yapılar ele alınmıştır. Bu betonarme çerçeve yapılar için öteleme analizleri DRAIN 2D programı ile yapılmıştır. Öteleme analizlerinin ardından zaman tanım alanında dinamik analizler gerçekleştirilmiştir. Öteleme analizleri, zaman tanım alanında dinamik analiz sonuçları ile karşılaştırılmıştır. Bu karşılaştırmanın ardından kırılganlık analizleri yapılmıştır. Betonarme çerçeve yapıların olasılıklı sismik davranışını ortaya koymak amacı ile kırılganlık analizleri ile kırılganlık eğrileri elde edilmiştir. Çalışmanın ana amacı, öteleme analizleri ile zaman tanım alanında dinamik analizlerin karşılaştırılması sonucu, daha gerçekçi bir sismik davranış tanımlama ihtiyacının olduğunu göstermek ve kırılganlık analizleri ile, sismik davranışın olasılıklı olarak daha gerçekçi bir şekilde ifadesini sağlayabilmektir.Article Citation - WoS: 40Citation - Scopus: 37Investigation of Interlayer Hybridization Effect on Burst Pressure Performance of Composite Overwrapped Pressure Vessels With Load-Sharing Metallic Liner(SAGE Publications, 2020) Kangal, Serkan; Kartav, Osman; Tanoğlu, Metin; Aktaş, Engin; Artem, Hatice SeçilIn this study, multi-layered composite overwrapped pressure vessels for high-pressure gaseous storage were designed, modeled by finite element method and manufactured by filament winding technique. 34CrMo4 steel was selected as a load-sharing metallic liner. Glass and carbon filaments were overwrapped on the liner with a winding angle of [+/- 11 degrees/90 degrees(2)](3) to obtain fully overwrapped composite reinforced vessel with non-identical front and back dome endings. The vessels were loaded with increasing internal pressure up to the burst pressure level. The mechanical performances of pressure vessels, (i) fully overwrapped with glass fibers and (ii) with additional two carbon hoop layers on the cylindrical section, were investigated by both experimental and numerical approaches. In numerical approaches, finite element analysis was performed featuring a simple progressive damage model available in ANSYS software package for the composite section. The metal liner was modeled as elastic-plastic material. The results reveal that the finite element model provides a good correlation between experimental and numerical strain results for the vessels, together with the indication of the positive effect on radial deformation of the COPVs due to the composite interlayer hybridization. The constructed model was also able to predict experimental burst pressures within a range of 8%. However, the experimental and finite element analysis results showed that hybridization of hoop layers did not have any significant impact on the burst pressure performance of the vessels. This finding was attributed to the change of load-sharing capacity of composite layers due to the stiffness difference of carbon and glass fibers.Article Citation - WoS: 16Citation - Scopus: 24Developing Polymer Composite-Based Leaf Spring Systems for Automotive Industry(Walter de Gruyter GmbH, 2018) Öztoprak, Nahit; Güneş, Mehmet Deniz; Tanoğlu, Metin; Aktaş, Engin; Eğilmez, Oğuz Özgür; Şenocak, Çiler; Kulaç, GedizComposite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance.Article Construction Techniques of Hayat Houses: Two Case Studies in the Vicinity of Izmir(American Society of Civil Engineers (ASCE), 2019) Turan, Mine; Aktaş, Engin; Mamaklı, Fatma Sezgi; Kaplan, ZişanThis study aims to contribute to the analytic studies on constructional aspects of the hayat house typology with an eye on its historical evolution for conservation purposes. The method used included a review of the surviving examples of the typology in Izmir and its vicinity and the selection of two intact examples whose structural components are legible: one from the earliest period and the other from the latest period. The examples selected are Kerimaga Konagi in Birgi, odemis, Izmir and a house in Kirkagac, Soma, Manisa. The early example (probably eighteenth century, constructed over the remains of an older house) sustains the traditional box system in its wooden upper story that integrates with the roof. The provision of level differences on the upper floor, the traditional relationship of the sitting level-window design, and masonry base are its authentic features. The late example (probably early twentieth century) presents signs of modernization, such as the establishment of a systematic wooden roof and wall frames in relation to each other, lack of diagonals in the perpendicular wall frame, avoidance of projections, and relatively elongated windows placed at higher positions.Article Citation - WoS: 6Citation - Scopus: 4Conservation-Aimed Evaluation of a Historical Aqueduct in Izmir(American Society of Civil Engineers (ASCE), 2019) Mamaklı, Fatma Sezgi; Turan, Mine; Aktaş, Engin; Vardaroğlu, MustafaThe seventeenth century was the era in which Izmir became an international commercial center in the eastern Mediterranean. The vizier of the era, Koprulu Fazil Ahmet Pasa, noticed the scarcity of potable water in relation with the increasing population at the center of this harbor city and ordered the construction of an aqueduct on Melez Valley. The Veziraga Aqueduct was constructed in 1674. This article aims to identify historical, architectural, and structural characteristics of the Veziraga Aqueduct so that its heritage values and conservations problems can be understood. The geographical and historical characteristics of the Veziraga Aqueduct are described by taking the effects of site and the sociocultural situation of city into consideration. The architectural characteristics of the aqueduct are prepared by using the site survey data to reveal the current condition and find out the original state. Seismic behavior of the aqueduct is investigated by using two approaches: analytical equivalent static analysis and finite-element analysis. The historical, architectural, and structural characteristics of the Veziraga Aqueduct prove its historical, documentary, and aesthetic values.Article Citation - WoS: 23Citation - Scopus: 26Experimental and Statistical Analysis of Carbon Fiber/Epoxy Composites Interleaved With Nylon 6,6 Nonwoven Fabric Interlayers(SAGE Publications Inc., 2020) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, EnginThermoplastic interleaving is a promising technique to improve delamination resistance of laminated composites. In this study, plain-weave carbon fiber/epoxy composites were interleaved with nylon 6,6 nonwoven fabrics with an areal weight density of 17 gsm. The carbon fiber/epoxy composite laminates with/without nylon 6,6 nonwoven fabric interlayers were manufactured by VARTM technique. Double cantilever beam fracture toughness tests were carried out on the prepared composite test specimens in accordance with ASTM 5528 standard. The experimental test data were statistically analyzed by two-parameter Weibull distribution. The results showed that the initiation and propagation fracture toughness Mode-I fracture toughness of carbon fiber/epoxy composites could be improved by about 34 and 156% (corresponding to a reliability level of 0.50) with the incorporation of nylon 6,6 interlayers in the interlaminar region, respectively. The results also revealed that the percent increase in the propagation fracture toughness value was 67 and 41% at reliability levels of 0.90 and 0.95, respectively.Article Citation - WoS: 31Citation - Scopus: 33Modification of Carbon Fibre/Epoxy Composites by Polyvinyl Alcohol (pva) Based Electrospun Nanofibres(Adcotec Ltd., 2016) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, EnginIn this study, the effects of modifying interlaminar region of unidirectional carbon fibre/epoxy composites by the incorporation of electrospun polyvinyl alcohol (PVA) nanofibres were investigated. PVA nanofibres were directly deposited onto the carbon fabrics by electrospinning method to improve mechanical performance of those composites. The features of the electrospun nanofibres were characterized by microscopy techniques. The unidirectional carbon fibre/epoxy composite laminates with/without PVA nanofibre interlayers were manufactured by vacuum-infusion technique in a [0]4 configuration. Tensile, three-point bending, compression, Charpy-impact and Mode-I fracture toughness tests (Double Cantilever Beam (DCB)) were carried out in accordance with ASTM standards to evaluate mechanical performance of the composites. Scanning electron microscopy (SEM) observations were made on the specimens to evaluate microstructural features. It was observed that the carbon fabrics were successfully coated with a thin layer of PVA nanofibres by electrospinning technique. The results showed that P VA nanofibres improve the mechanical properties of unidirectional carbon/epoxy composite laminates when subjected to in-plane loading. On the other hand, PVA nanofibres slightly reduced the mode-I fracture toughness values although they led to more stable crack propagation.Article Citation - WoS: 108Citation - Scopus: 117Enhancement of Interlaminar Fracture Toughness of Carbon Fiber–epoxy Composites Using Polyamide-6,6 Electrospun Nanofibers(John Wiley and Sons Inc., 2017) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, EnginIn this study, carbon fiber–epoxy composites are interleaved with electrospun polyamide-6,6 (PA 66) nanofibers to improve their Mode-I fracture toughness. These nanofibers are directly deposited onto carbon fabrics before composite manufacturing via vacuum infusion. Three-point bending, tensile, compression, interlaminar shear strength, Charpy impact, and double cantilever beam tests are performed on the reference and PA 66 interleaved specimens to evaluate the effects of PA 66 nanofibers on the mechanical properties of composites. To investigate the effect of nanofiber areal weight density (AWD), nanointerlayers with various AWD are prepared by changing the electrospinning duration. It is found that the electrospun PA 66 nanofibers are very effective in improving Mode-I toughness and impact resistance, compressive strength, flexural modulus, and strength of the composites. However, these nanofibers cause a decrease in the tensile strength of the composites. The glass-transition temperature of the composites is not affected by the addition of PA 66 nanofibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244.Conference Object Citation - WoS: 11Citation - Scopus: 14Quantitative Detection of Low Energy Impact Damage in a Sandwich Composite Wing(SAGE Publications Inc., 2010) Seaver, Mark; Aktaş, Engin; Trickey, Stephen T.This work describes damage detection in a foam core composite wing (1320 mm × 152.4 mm × 13.4 mm) following a series of low energy impacts. Thirteen impacts (6-8 J deposited energy) were applied at adjacent locations approximately 1/4 of the way out from the wing center. Following every one or two impacts, the wing was tested using static tip deflection and dynamic vibrational excitation. Static and dynamic strains were measured using eight fiber Bragg grating sensors. Dynamic acceleration was also monitored using three conventional accelerometers. The estimated bicoherence was used to detect the presence of damage-induced non-linearity in time-series data recorded from each sensor. Receiver operating characteristic (ROC) curves were constructed for each sensor based on 15 or more dynamic measurements made for each damage case. The ROC curves provide a quantitative, statistical approach to evaluating the damage detection capabilities of the various sensors.