Master Degree / Yüksek Lisans Tezleri
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Master Thesis Yaşlanan Ceket Tipi Açık Deniz Yapılarının Yaşam Döngüsü Performansı: Güvenirliliğe Dayalı Tasarım için Korozyon, Yorulma ve Afetlere Karşı Dirençliliğin Entegrasyonu(2025) Yıldırım, Efe Mert; Aktaş, EnginMühendislik yapıları, zamanla dış ve çevresel yükler nedeniyle bozulma gösterir ve arıza riski taşır. Yapısal dirençlilik analizi, bu yapıların kesintilere karşı koyma ve işlevselliğini koruyarak toparlanma yeteneğini değerlendirir. Doğu Akdeniz'de artan petrol ve gaz arama faaliyetleri, açık deniz platformlarına olan talebi yükseltmiştir. Bu yapılar, korozyon, çatlaklar ve hidrokarbon sızıntıları kaynaklı patlama ve alev alma gibi zorlu koşul ve afetlerle karşılaşır; bu nedenle dayanıklı ve güvenilir tasarımlar gereklidir. Bu tez, yaşlanan denizaşırı platformların tekli yük olayları altındaki zamanla değişen direncini incelemektedir. Çalışma, hidrokarbon sızıntıları kaynaklı patlama ve alev alma, yorulma çatlakları ve korozyon kaynaklı incelmeye odaklanarak, Levanten Denizi'nin benzersiz çevresel koşullarında birikimli hasar mekanizmalarının etkisini analiz eder. Zamana bağlı bir direnç değerlendirme modeli kullanılarak, yapısal dirençteki azalma incelenmiştir. Korozyon ve çatlak ilerlemesi, özellikle en hassas bölgeler olan dalgaların çarptığı ve sualtı bölgelerinde, doğrusal bozulma fonksiyonlarıyla modellenmiştir. Analiz, 15 ve 50 yıllık hizmet ömürlerini kapsayarak kısa ve uzun vadeli dirençliliği ve güvenilirliği değerlendirir. Bu faktörlerin entegre edilmesiyle, araştırma, aşırı deniz ortamlarında denizaşırı platformlarının uzun süreli stres altındaki davranışına ışık tutarak daha güvenli ve dirençli tasarımların geliştirilmesine katkı sağlarMaster Thesis The Structural Conservation Problems of Traditional Houses in Eryeri, Mardin, Artuklu(01. Izmir Institute of Technology, 2023) Ercan Gündüz, Yasemin; Turan, Mine; Aktaş, EnginThe aim of this study is to document the construction techniques, material usage, and structural failures of the traditional houses in a village of Mardin, Eryeri, in order to guide a conservation aimed development plan that will be prepared in the future and enhance the related rehabilitation implementations. Eight houses that have preserved their authenticity were selected. Field survey focusing on the structural elements such as foundations, walls, floors, and roofs was conducted with the conventional techniques of architectural restoration. Both failures and also alterations of the buildings were documented. The changes and alterations of the houses are documented. Visual analysis of the constructional qualities was made with Archicad23 tools. Comparison with the traditional houses in the vicinity was made with reference to data gathered via field survey, literature review and archive research. As a result, the traditional houses are integrated with the rocky terrain of the region and in masonry system. There is an intense use of local stone, Yellow Limestone. Vaults are common superstructure elements, but timber floor is also possible. The walls are stone masonry in all. The common structural problems are demolition of structural elements such as roofs. The causes of severe failures are neglect and natural aging. The reinforced concrete additions flanking to the authentic structures also cause failure. Within the scope of the conservation plan, it is important to prevent reinforced concrete annexes and to intervene the annexes that cause excessive loads urgently.Master Thesis Application of Artificial Neural Networks To Structural Reliability Problems(01. Izmir Institute of Technology, 2023) Köroğlu, Fahri Baran; Aktaş, Engin; Maguire, MarcThe contemporary approach in structural engineering indirectly addresses uncertainties arising from load and resistance parameters by using safety factors. To consider these uncertainties in structural engineering, it is necessary to incorporate their statistical properties into the analysis and design process. However, this approach requires the calculation of challenging multi-fold probability integrals. Approximate methods known as FORM and SORM have been developed as an alternative to calculating those integrals. Unfortunately, these methods might have accuracy and convergence problems depending on the problem at hand. Simulation-based structural reliability methods have been developed to overcome the problems associated with approximate methods. The main problem with these methods is that they are often computationally expensive when along with finite element analysis, or it is hard to implement them when a more specific method is chosen to reduce computational costs. In this study, artificial neural networks have been applied to structural reliability problems to obtain accurate probability estimates with low computational cost. A special type of learning algorithm called Bayesian Regularization was used in the training of artificial neural networks. Additionally, details of the application of artificial neural networks to structural reliability problems are provided. At the end of the study, the advantages and disadvantages of applying artificial neural networks to structural reliability problems are presented and compared with other known structural reliability methods. Additionally, a new convergence criterion and an adaptive algorithm have been developed. It was observed that applying artificial neural networks to structural reliability problems provides both efficient and accurate probability estimates.Master Thesis Seismic Vulnerability Assessment of Bergama Bedesten(Izmir Institute of Technology, 2022) Demir, Hatice Ayşegül; Turan, Mine; Aktaş, EnginThis study aims to document Bergama Bedesten with emphasis on its construction technique and material usage; and assess its structural condition for future seismic action through numerical analysis. The monument (15th -16th century) is unique among the historical trade buildings at the center of Bergama, İzmir. It is revealed that the structure is a rare example by the use of plane triangles as transition elements, the oculi placement in domes, and the thickening application at parts where load-bearing arches integrate into the walls and at the corners. In order to investigate the vulnerability of the building, numerical analysis using the finite element method was conducted in ANSYS software. According to the Turkey Building Earthquake Code (2018), single-mode equivalent earthquake analysis considering the horizontal elastic design spectrum of the site was carried out for x and y directions, separately. The maximum principal stress concentration locations obtained through analyses point vulnerable zones. These were specifically observed on load-bearing arches, on some plane triangles, on the transition zones, at dome parts close to the transition zone and peak level, at the parts where arches integrate to the walls, around top windows, on the west entrance door arch, and on a secondary door arch in the north wall. The method comparing the structural failure mapping and visual structural alterations analysis of architectural restoration with finite element model results, emphasizes that some damaged or altered portions in the current state are in seismically vulnerable spots. Some precautions, further studies and interventions were suggested for these locations.Master Thesis A Practical Finite Element Model of Tsadwa Type Semi-Rigid Connections for Push-Over Analysis of Steel Frames in Sap2000(01. Izmir Institute of Technology, 2021) Şeker, Öncel; Aktaş, EnginIn steel structural analyses, beam to column connections is traditionally fully pinned or fully rigid. In the analysis assumption, moment (rigid) connections are assumed not to undergo rotation, and shear (pinned) connections can't transfer moment. These classifications do not represent actual connection behavior. Moment (rigid) connections have some relative flexibilities to rotate, and shear (pinned) connections have some capacity to transfer moment. In the light of these actual connection capabilities, another type of connection called partially restrained (PR) or semi-rigid connection is introduced. This study focuses on the behavior of bolted top, and seat angle with double web angle (TSADWA) connection using finite element method (FEM) software (ANSYS) to obtain moment-rotation curves, including geometrical and mechanical properties of the connection and adaptation of the PR connection behavior into the planar frame is performed for performance analysis through SAP2000 software by considering current codes and literature. Azizinamini's (Azizinamini, 1985) experimental and Frye and Morris's (Frye & Morris, 1975) mathematical moment-rotation curves are used to compare with the curves produced in the ANSYS to validate the feasibility of the finite element based PR connection models. A portal frame model with an 8S10 PR connection in the SAP2000 for performance analysis is also compared with the ANSYS portal frame model to demonstrate the correlation between the push-over analysesto reduce the margin of error. Although there is a lack of experimental information on the TSADWA connected frame models, results show that semi-rigid connection models and their usage on the steel frames can propose a reliable and practical methodology for the analysis process.Master Thesis Reliability Based Seismic Assessment of Unanchored Circular Steel Storage Tanks(Izmir Institute of Technology, 2020) Bektaş, Nurullah; Aktaş, EnginSince liquid storage tanks are important systems for the safety of industrial facilities, the tightness of these structures and their serviceability are key issues. Therefore, the ability of large liquid storage tanks to withstand damage during earthquakes is of great relevance not only to the engineering profession but also to the safety of society in general. This is because these structures often form an important part of a community's lifeline and therefore should remain in use in emergency situations. In addition, since the content stored in some facilities could be hazardous, in this case, necessary measures must be taken against accidental infiltration. Due to the importance of storage tanks for society, there are many studies and standards in the literature on the behavior of liquid storage tanks. The most detailed method is the incremental dynamic analysis, which considers the time history analysis within a finite element model for the seismic analysis of unanchored circular steel liquid storage tanks to assess performance. In this study, a performance-based study was conducted on the dynamic behavior of an unanchored circular steel liquid storage tank in order to consider possible improvements in the design phase of the model to withstand earthquakes. It is assumed that the tanks stand on a rigid foundation and are exposed to one-way horizontal ground motion. The main purpose of the study is to determine the performance of the structure for certain failure criteria by using the engineering program ABAQUS to perform reliability-based analyzes of the model.Master Thesis Structural Model Besed Root Cause Investigation of Damage in Urla Helvacılar Mosque and a Proposal for Strengthening(Izmir Institute of Technology, 2019) Narin Güzel, Ceren; Kul Özdemir, Fatma Nurşen; Aktaş, EnginThe period when small independent beyliks (principalities) were founded in Anatolia in the 13th century is called the principalities period. The process of creating a new architectural style in Western Anatolia, as well as the works-built marks an important milestone in this period, which is defined as a transition period between the Seljuk architecture and the Ottoman architecture. The Aydın Dynasty, one of the important principalities of western Anatolia, had its capital at Birgi from 1308 to 1426. The dynasty is known for with its economic and political power and the important works it left behind. Helvacılar Mosque is one of the important works of the Aydın Dynasty, which was built in the 15th century and survives today. It is also an outstanding example to understand the single-domed mosque typology in western Anatolia. Helvacılar Mosque, located in the Kuşcular Neighborhood of the Urla District, is today derelict and abandoned. Heavy structural damage in the structure poses a grave risk for the structure to survive. This study compared and discovered the similarities and differences between Helvacılar Mosque and the similar-period structures situated in Urla and identified the architectural and structural characteristics of the structure with the aid of measured drawing projects. This study used a combination of architectural restoration and structural engineering. For Helvacılar Mosque, the study carried out the self-weight analysis, modal analysis, settlement analysis, response spectrum analysis, time history analysis using three real earthquake records in a finite element model. The aim of engineering research is to identify the present causes of damages in the structure. With the help of finite element analysis, the study put forward the essential repair and strengthening methods for Helvacılar Mosque to repair the damages observed in the structure, strengthen the structure, and obviate the causes of the damages based on the intervention methods offered in the guideline titled Earthquake Risk Management of Historical Structures issued by the General Directorate of Foundations.Master Thesis Structural Analyses and Assessment of Historical Çardak Caravanserai in Denizli(Izmir Institute of Technology, 2019) Şahin, Esra; Aktaş, Engin; Turan, MineThe assessment of historical masonry structures are significant in terms of transferring our cultural heritage to future generations. The conservation of these masonry structures is possible through investigating problems and their causes with tools such as structural modeling and analyses. In this study, the structural modeling and analyses of a historical masonry structure was aimed. Çardak caravanserai in Denizli was chosen as the case study since it has preserved its authenticity and integrity. In this scope, the software used for modeling and structural analyses was SAP2000 v20.2 commercial finite element software. For modeling, frame elements were used in the columns and shell elements were used in the other structural elements. Selfweight analysis, modal analysis and response spectrum analysis were conducted in terms of the assessment. The self-weight analysis was made under dead load. The analysis indicated the current state of the structure. In modal analysis, free vibration periods, mode shapes and mass participation ratios of the structure were determined. In response spectrum analysis, according to Turkish Siesmic Design Code 2018, mode integration method was used as linear calculation method. In this analysis, the khan was evaluated under the dead load and earthquake loads in the x and y directions. The structural elements that exceed the compressive, tensile and shear strength were identified as hot spots and recommendations on the further investigations on these critical points of the structure were presented.Master Thesis Evaluation of Behaviour Factors of Steel Moment Resisting Frames(Izmir Institute of Technology, 2019) Baran, İbrahim; Aktaş, Engin; Kanyılmaz, AlperBuilders of structures throughout the history of civilizations have been challenged with various threats. Earthquakes, which may be considered as the most critical challenge of the built environment have been one of the main concerns of builders at all times especially in regions with high earthquake risk. In this study, Response Modification Factor, (also known as ‘R’ or ‘q’ factor) which is used by seismic codes to determine force demand considering the ductile behaviour of the structure during the earthquake, has been analyzed. Steel frames (36 frames) with a different number of stories (3,6,9) and bays (3 to 8) were designed with normal ductility (18 frames) and high ductility (18 frames) moment resisting steel frames. The Turkish Building Earthquake Code-2018 (TBEC 2018) was followed for the seismic design process. All frames were assumed to be constructed in a region with the highest seismic demand defined in the web-based Hazard Map in TBEC 2018. The performance evaluation of the designed frames is completed using non-linear static analyses following FEMA, ATC-40 and NEHRP guidelines. The non-linear static analyses were implemented with SAP2000 v20.2 commercial software. Static pushover analysis as well as the capacity curve graph, known as the N2 method, has been obtained, and the position of the frame capacity in the spectral acceleration graph has been determined and presented visually. The results were summarized and the R factors obtained from these analyses were compared with the values given in the Turkish Building Earthquake Code.Master Thesis Project Plannig and Management Using Building Information Modeling (bim)(Izmir Institute of Technology, 2018) Politi, Ruti Ruth; Aktaş, Engin; İlal, Mustafa EmreToday, in construction practice, implementation of effective construction management techniques and tools is becoming essential, especially as the scale of the projects increases. Large scale projects pose a challenge to industry; as the number of tasks, parameters and constraints to be considered rises, interaction of these tasks and parameters increases the complexity, as well. While the search for techniques and tools for better coping with complexity will never end, Building Information Modeling (BIM) has recently emerged as an approach that achieves considerable improvement in efficiently handling complexity. BIM is able to provide a digital visualization of a building or structure in 3D. The necessary geometric data is modeled but more importantly all semantic data associated with the project (function of the element, material properties, construction details, schedules, etc.) is stored with the model. The intent is to have a single model of the project for all stakeholders over all phases of the project. In this study, the main challenges within the current practice of project management are analyzed and what BIM-based project management has to offer to those challenges have been discussed. The thesis explores how BIM method can be applied to project management and how information can be collected to build a BIM model. The advantages of BIM-based scheduling (4D), cost estimation (5D), sustainability (6D), facility management (7D) and structural analysis in the scope of project management is discussed. A case study is given to validate the use of the computer aided programs for nD BIM during the construction phase.