Civil Engineering / İnşaat Mühendisliği

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  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Consolidation of a Bath Ruin in an Archaeological Site
    (Taylor and Francis Ltd., 2022) Durmuşlar, Feyza; Turan, Mine; Yücetürk, Kutay; Aktaş, Engin
    The study has focused on consolidation of a historical bath ruin in an archaeological site. Cevher Pasa Bath, which is located in Tabae archaeological site in Denizli, Turkey and dated to the 15th century, presents structural problems. The aim of the study is to propose a framework for planning consolidation of the ruins of Cevher Pasa Bath so that conservation work regarding similar masonry ruins in archaeological sites can be guided. Thus, methods of architectural restoration and civil engineering are combined in an interdisciplinary scope. Provision of temporary shoring as an emergency intervention, consolidation and presentation of the ruin within the scope of an interdisciplinary restoration project, and monitoring of the asset within the frame of a monument management plan are suggested, respectively. Structural analysis considering stress and overturning moment checks are performed. Consolidation work includes only supporting of arch remains. Some walls of the ruin are weaker than other parts. These parts need further detailed analysis, and if necessary, further consolidation and strengthening are to be carried out. The monument management plan points out the necessity of collaboration of local and central administrations, and also non-governmental organisations.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Proposals for Monitoring Current Conservation Condition of Historical Masonry Buildings: Matrone Church and Çardak Han Cases;
    (Istanbul University Press, 2020) Durmuşlar,F.; Ipekci,E.; Turan,M.H.; Aktaş,E.
    The aim of this study is to transfer the international developments related to the process of diagnosis and monitoring of historical masonry structures to the national area. The method chosen is to test the recommendations made at the international level on national cases and to discuss the results obtained by comparing them. A review of preliminary studies, on-site observations, measured surveys, material characterizations, mapping and visual analysis have been carried out. An examination of structural characteristics and observed failures have also been detailed. Related risks have been evaluated with criteria developed by taking into consideration condition classes defined in the UNI EN 16096, titled Conservation of Cultural Property - Condition Survey and Report of Built Cultural Heritage. According to the defined risks and classes, priorities of interventions were determined. Two historical masonry buildings which possess characteristics of different periods and present different damage types were selected: Matrone Church in Ildiri, Çeşme, Izmir and Çardak Han in Çardak, Denizli. The condition reports of the selected buildings have been prepared. The critical points in the condition reporting of historical masonry buildings were determined: accurate comprehension of the authentic structural characteristics and related failures have priority in maintaining historical masonry structures. Identification of condition class and risk assessment of each historic masonry building should be made in accordance with a standard specific to the cases of our country, but in line with the European standards and current developments in the field of architectural restoration. Thus, it will be possible to evaluate the conservation state of our masonry assets in comparison with each other. The content and priority of interventions can be well planned with the participation of the necessary disciplines. © 2020 The authors.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Structural Vulnerability of Ancient Dry Masonry Towers Under Lateral Loading
    (Elsevier, 2020) Gençer, Funda; Hamamcıoğlu Turan, Mine; Turan, Mine; Aktaş, Engin; Aktaş, Engin
    Understanding how the original characteristics contribute to the structural behaviour of antique structures should be the initial stage of planning for conservation work. This study aims to identify the structural behaviour of dry masonry towers under lateral loadings, so that the decision-making process when determining their restoration can be adequately supported. Dry masonry towers in ancient Caria, Pamphylia, and Cilicia Regions are examined. Each of these three areas have very different seismic characteristics. A hypothetical testing process was designed by combining different characteristics from each of the towers. As a result, the characteristics affecting the structural resistance were determined as; the staggering ratio, the stone depth, the ratio between block length and height, the proportional relationship between height and length, the area, number and position of openings, and the distribution of header stones. These characteristics all interact together to determine the failure mechanism; so, understanding this interaction is critical when considering conservation. © 2020 Elsevier Ltd
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 2
    Structural Comparison of Scissor-Hinge Linkages
    (CRC Press, 2019) Maden, Feray; Akgün, Yenal; Yücetürk, Kutay; Aktaş, Engin; Yar Uncu, Müjde; Mitropoulou, C.
    Deployable structures can deploy from a compact to an expanded configuration by changing their sizes. The behaviors of these structures depend on some parameters such as geometric shape, member sizes and kinematic properties. To provide the deployment, not only the arrangements of structural members but also some restrictions must be considered. Moreover, contiguous members of the structures must let the large rotations to provide the transformation between different geometric forms from fully folded to fully deployed configurations. These requirements have an important impact on the fundamental properties of the structures related with structural performance, such as stiffness and strength. In this paper, stiffness of different scissor-hinge linkages are analyzed and compared. These linkages cover the same span with almost the same geometry and have the unit elements with same size and same weight. However, the geometry of unit elements is different from each other. The paper investigates the effect of this difference on the stiffness of whole system. © 2019 Taylor & Francis Group, London.
  • Conference Object
    Citation - WoS: 2
    Citation - Scopus: 2
    A Case Study on the Selection of Optimum Loop Units for the Deployable Arch Structures Exposed To Lateral and Non-Uniform Gravity Loads
    (Elsevier, 2020) Yuceturk, K.; Aktas, E.; Maden, F.; Gur, S.; Mitropoulou, C. C.
    Radially deployable arches may be created by using various types of units. However, for any deployable structure to be constructed in real life, it should satisfy the structural regulations and codes. Despite various advantages from architectural perspective, deployable structures are weak to satisfy the operational code limits when compared to trusses with similar height and span. Therefore, weight minimization is very important to reduce the dead loads of the structure which facilitates the code-conformance of the structure. The optimization of the deployable structures requires an initial selection of the loop types to define the structure parametrically. An initial selection strategy depending on the loads on the structure is important to increase the efficiency of optimization process. Under uniform gravity loads, optimum arrangement for each unit type converges to a similar point. However, in the real world, the loads on the arches are not always uniform and the structure is exposed to nonuniform loadings such as point loads or lateral loads. This work focuses on the performance of various arches with different unit types under lateral and non-uniform vertical loads. Different lateral load and non-uniform gravity loading scenarios are created. For each scenario, the arches with different units are analyzed. In all cases, clear span and height are kept as same. The performance of an arch with a specific unit type for a given load is measured with a score that includes the deformations and the weight of the structure. All the members are assumed to be circular hollow sections with variable diameter and thickness to have a meaningful weight comparison between structures. This work intends to define an initial selection guide for deployable arches under typical non-uniform and lateral loading conditions. (C) 2020 The Authors. Published by Elsevier B.V.
  • Conference Object
    Roc Curves for Evaluating Sensor Performance as Low Energy Impacts Damage a Composite Wing
    (DEStech Publications Inc., 2009) Aktaş, Engin; Seaver, M.
    Eight fiber Bragg gratings and 3 ICP accelerometers attached to the upper surface of a foam core composite wing (1320 mm X 152.4 mm X 13.4 mm) were used to record the wing's response to broad band (0 - 1500 Hz) Gaussian excitation following a series of low energy (-6.5 J) impacts to the surface of the wing. For each damage level, at least 15 measurements were made over a period of three days to enable a statistical evaluation of each sensor's performance. Damage detection relied on measuring nonlinearity in the response data using a second order correlation metric called the Bicoherence. The amplitudes of any peaks seen in the Bicoherence were compared with thresholds determined from the variance in the off diagonal terms in the Bicoherence measurement. This approach allows the evaluation of both the probability of detection (POD) and the probability of false alarms (PFA) for each measurement without the need for a healthy baseline. The results show that all eight FBGs out perform the accelerometers and that one FBG in particular is more sensitive to nonlinearity than the others. The measurement sensitivity of the Bicoherence is also compared with static tip deflection measurements.
  • Article
    Citation - WoS: 40
    Citation - Scopus: 37
    Investigation 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 Seçil
    In 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: 16
    Citation - Scopus: 24
    Developing 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, Gediz
    Composite-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
    Citation - WoS: 39
    Citation - Scopus: 40
    Mode-I Fracture Toughness of Carbon Fiber/Epoxy Composites Interleaved by Aramid Nonwoven Veils
    (Techno Press, 2019) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, Engin
    In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of 8.5 g/m(2) to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites.
  • 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, Zişan
    This 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.