Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Structural Health Monitoring of Small-Scale Vertical Axis Wind Turbine Blade(Izmir Institute of Technology, 2023) Öğünç, Ozan; Turan, Gürsoy; Turan, Gürsoy; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologySon yıllarda, Dünya genelinde ve Türkiye'de enerji fiyatlarında büyük artışlar yaşanmaktadır. Bu artışların yanı sıra fosil yakıtların doğaya verdiği zarar yenilenebilir enerji kaynaklarına olan ilgiyi daha da arttırmıştır. Yenilenebilir enerji kaynaklarından olan rüzgar, bu ilginin odak noktalarından biri olmuştur. Rüzgardan gelen kinetik enerjiyi elektrik enerjisine dönüştüren rüzgar türbin sistemleri farklı mühendislik hizmetlerinin uygulanması ile oluşturulur. Dünyadaki hızlı teknolojik değişim ve rüzgara olan ilgiden dolayı son yıllarda rüzgar türbin sistemleri çok hızlı bir şekilde gelişme göstermiştir. Rüzgar türbinlerinin sayısının ve öneminin artması ile bu tarz yapıların sağlığının incelenmesi önemli bir konu olmuştur. Bu tez çalışmasında, XGEN-Energy firmasının ürettiği Wind-Er modelinin kanadı incelenmiştir. Türbin kanadının öz frekanslarını ve mod şekillerini belirlemek için python dili kullanılarak, kovaryans güdümlü stokastik alt uzay tanımlama yöntemi (SSI-Cov) programlanmıştır. Çalışma iki temel kısımdan oluşmaktadır. İlk kısımda, kanat modeli python yazılım dili ile parametrik tasarım yapılmış ve CalculiX sonlu elemanlar programı kullanılarak modal analizi yapılmıştır. Modal analiz tamamlandıktan sonra uygun deney düzeneğine karar vermek için transient analizi yapılmıştır. Analiz sonucu çıktı verileriyle SSI-Cov yöntemi test edilmiştir. İkinci kısımda, kanadın fiziksel modeli üzerinde testler yapılmıştır. Sayısal model ile fiziksel model çıktı verileri birbirini doğrulamıştır. Modelin modal parametrelerinden, doğal frekansları ve ilk modun mod şekilleri SSI-Cov kullanılarak tahmin edilmiş ve sonuçlar tutarlı çıkmıştır.Master Thesis Modal Parameter Identification of Civil Engineering Structures by Using an Output-Only System Identification Technique(Izmir Institute of Technology, 2015) Ceylan, Hasan; Turan, Gürsoy; Turan, Gürsoy; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyCivil engineering structures are designed for a limited lifetime. Due to environmental effects and degradation of these structures, engineers need to decide on their structural safety and sustainability from time to time. To this end, structural health monitoring techniques could be employed to determine the current structural state. Current conditions of structures could be investigated by system identification techniques that is based on the modal parameters (modal frequencies, modal damping ratios and mode shapes) of structures. In this thesis, output-only system identification of civil structures is studied to estimate modal parameters of two different types of structures. For this purpose, a combination of the Natural Excitation Technique (NExT) and the Eigensystem Realization Algorithm (ERA) is coded within Matlab environment. The first study consists of a numerical and an experimental phase. In the numerical phase, the technique is implemented on the mathematical model of a three-story model building. In the experimental phase, it is implemented on the physical model of this three-story model building. 10 different scenarios of structural conditions are simulated by means of changes in story masses of the structure. By using NExT-ERA, the calculated modal frequencies and mode shapes are in good agreement with the results of the eigenvalue analysis. Further, the simulated mass change in each scenario is detected by a least squares approach. Changes in story masses are detected within reasonable errors. In the second study, a methodology is proposed to acquire measurements of large structures by using a few sensors, only. These sensors are used in a segmental way to measure the whole structure. The sensors are grouped and the groups of sensors are shifted on the model to obtain the response measurements from the whole structure. Then the grouped response measurements that are obtained at different time frames are transformed into the equivalent response data as if being acquired at a single time interval. To implement the methodology, a finite element model of a continuous beam bridge is constructed. Modal parameters of the model are estimated by using NExT-ERA and the results show that the first 10 modal frequencies are consistent with those of the eigenvalue analysis of the model, but only the first 6 mode shapes are successfully identified.Master Thesis Preliminary Design and Analysis for Immersed Tube Tunnel Across the Izmir Bay(Izmir Institute of Technology, 2008) Kartaltepe, Nisa; Turan, Gürsoy; Turan, Gürsoy; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, a preliminary design and analysis of an immersed tube tunnel is presented. The tube tunnel will connect the two coasts of the İzmir Bay and whereby will ease the transportation of the city. The reason to suggest an immersed tube tunnel is due to the shallow water depth (<25 m) and that the soil profile of the İzmir Bay is made up of silty-sand. Hence, the Bay is appropriate for an immersed tube tunnel.First, a possible alignment was assigned for the tunnel. The technical, geometric properties of the tubes were determined, and the detailed drawings of them were made.The allowable bearing capacity of the seabed was calculated and it was determined that the soil has not enough capacity to withstand the design load. The liquefaction risk of the soil was investigated as well, and it was shown that the soil has high liquefaction potential.A static analysis of the tunnel was made in Calculix, a finite element program.The vertical displacement of the tube unit under static loads was calculated to be above the permissible settlement value. Afterwards, the seismic analysis was made to investigate stresses developed due to both racking and axial deformation of the tunnel during an earthquake. It was found that, the max stress due to the racking effect is less than the compressive strength of the concrete, and max stress due to the axial deformation is larger than compressive strength of the concrete. The high in the tube occur, because of the tubes high stiffness. This problem was solved by releasing the rigid connections in between two tube units. If these connections are made by using same form of elastomer joints, the deformation will occur in these joints, releasing the tubes internal stresses.Considering these drawbacks, ground improvement was recommended for the seabed and an increased value of the standard penetration of the soil was estimated.Then, the analyses were repeated and it was found that all drawbacks were eliminated.As a conclusion, it was decided that if suggested improvements are made in the seabed soil, the immersed tube tunnel can be constructed across the İzmir Bay.Master Thesis Earthquake Response of R/C Frames With Reinforced Infill Walls(Izmir Institute of Technology, 2008) Yıldırım, Umut; Turan, Gürsoy; Turan, Gürsoy; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyMost of the reinforced concrete structures that are built in the past few decades are in lack of ductility and lateral stiffness. In the content of the present work, a fast and economical remedy was searched to rehabilitate these type of buildings that are under high risk of earthquake damage.The strengthening technique needs to be finished in a short time without the people that live inside the buildings to move out. Furthermore, the chosen strengthening technique needs to be economical enough so that the home owner would not hesitate in making a decision of the rehabilitation.In regard of the above mentioned two criteria, existing infill clay brick walls may be strengthened by the addition of a wire mesh on the surface together with a layer of plaster. In order to investigate its effectiveness, a numerical investigation is carried out to study the behaviour of a strengthened infilled reinforced concrete (RC) frame using wire mesh under lateral reversed cyclic loading. A single span, one-story clay brick infilled RC frame is modeled and a nonlinear analysis is made.The analysis results indicate that the technique of strengthening with wire meshincreased the peak lateral load, ductility and energy dissipation.Master Thesis Construction and Control of a Desktop Earthquake Simulator(Izmir Institute of Technology, 2006) Kınay, Gökçe; Turan, Gürsoy; Turan, Gürsoy; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyA portable, servo motor driven, and single-degree-of freedom earthquake simulator is manufactured. The moving table has a dimension of 40 cm x 40 cm. It can carry a load of 80 kg, accelerated to 2 g (1 g @ 9.81 m/s 2 ). Its maximum displacement capacity is ± 7 cm. In order to obtain the desired motion, a voltage of .10 to +10 volts is applied to the servo unit (motor driver), which is adjusted to move the table at .25 cm/s and 25 cm/s, respectively. A runtime program is written to read an earthquake's velocity-time data and to produce an electrical voltage that takes care of the following two items: First, the maximum speed of the simulated earthquake can not be larger than the motor.s capacity. Second, the maximum earthquake displacement can not be larger than the table.s displacement capacity.In the present work, the recorded strong motion acceleration time series are processed in order to obtain useful data for engineering analysis. Strong motion accelerogram processing (earthquake data processing) is performed in Scilab. The objectives of strong motion data processing are corrections for the response of the strong motion instrument itself, and reduction of random noise in the recorded signals. The processing concentrates on the lowfrequency ranges of the usable signal in the records.The results obtained from comparison of the present work's outputs and some data providers' outputs are satisfactory. Some slight differences exist due to the different integration schemes and due to the application of different filter orders, zero-padding, and different filters for instance, acausal or causal Butterworth filter.The simulations are performed in a regular Linux environment and also in a Realtime Linux environment. The advantage of the realtime environment ensures the signals send to the servo driver to be on-time . no delay due to operating system tasks.Master Thesis Response Improvement by Using Active Control of an Earthquake Excited Building(Izmir Institute of Technology, 2004) Işık, Onur; Turan, Gürsoy; Turan, Gürsoy; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyTwo control laws are proposed to a 5-story government building that had been subjected to the 17 November 1999, Düzce, Turkey Earthquake. The building was moderately damaged although it had adequate size beams and columns, and relatively high concrete strength, unlike the remaining moderately damaged buildings in the area. The aim of this study is to investigate, if the building response could have been improved by using active control. Since the building was rigid, it was known that large control forces were needed. The implementation of a controller to a real structure with large control forces and amount would be unrealistic but to investigate the behavior, a 3-dimensional model of the five story building has been formed and 20 actuators, 4 at each level, are symmetrically placed and a control law is formed to improve the building response. Precautions to compensate for errors in the model and precautions about the time loss of the control system have been taken. Finally, closed loop simulations of the system shows that the building response can be improved by using active control, and possibly reducing and/or eliminating failure.Master Thesis Investigation of the Benefits of Variable Orifice Dampers Used in an Earthquake Excited Three Story Structure(Izmir Institute of Technology, 2009) Gökdağ, Hakan; Turan, Gürsoy; Turan, Gürsoy; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyResearch in the field of control of civil engineering structures is a continuing process. The three basic approaches to structural control may be defined as follows passive control systems,active control systems and semi-active control systems. These systems have received much attention recently because they have versatility and adaptability of active control systems. Although there is a wide variety of these energy absorbing devices, but all have one thing in common . they absorb energy from the structure.Semi-active control systems possess the advantages of both active and passive control systems. Variable orifice dampers are semi-active control devices that utilize the hydraulic fluid flow to generate controllable damping forces. Depending on the state of the structure, the energy absorbing property of the variable orifice dampers is changed on the fly. In this study, the proposed semi-active control algorithm and the effect of variable orifice damper for seismic response reduction is examined. To demonstrate the efficiency of the proposed semi-active control algorithm and the usefulness of variable orifice dampers,controlled and uncontrolled behaviour of the three story model structure subjected to earthquake forces are investigated numerically. The three story model structure in Civil Engineering Laboratory in .YTE is utilized for numerical simulations. The results indicate numerically that the proposed semi-active control algorithm with a variable orifice damper can be used effectively to reduce the earthquake induced structural vibrations.