Browsing by Author "Nohutcu, H"

Now showing 1 - 8 of 8
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    A NEW METHOD FOR STRENGTHENING OF PRECAST INDUSTRIAL STRUCTURES
    Kaplan, H; Yilmaz, S; Çetinkaya, N; Nohutcu, H; Atimtay, E; Gönen, H
    1998 Ceyhan and 1999 Marmara Earthquakes causes extensive damages of the precast industrial structures. This type of structures is important economically. They do not have enough lateral rigidity, lateral load capacity and a rigid diaphragm. Several strengthening techniques have been applied to those type of structures. However, minimization of the disturbance during the strengthening of these structures is an important research issue as considerable economic losses are to be happen while building remains out-of-service. In this study, effectiveness of the strengthening with external shear walls and rigid diaphragm is investigated experimentally. A typical precast concrete frame and a strengthened structure with proposed method are tested under reversed cyclic loads. Experiments showed that proposed method improves lateral stiffness, base shear capacity and provides an efficient diaphragm behavior to the structure.
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    Collapse mechanism estimation of a historical slender minaret
    Nohutcu, H; Hokelekli, E; Ercan, E; Demir, A; Altintas, G
    The aim of this study is to accurately estimate seismic damage and the collapse mechanism of the historical stone masonry minaret Hafsa Sultan, which was built in 1522. Surveying measurements and material tests were conducted to obtain a 3D solid model and the mechanical properties of the components of the minaret. The initial Finite Element (FE) model is analyzed and numerical dynamic characteristics of the minaret are obtained. The Operational Modal Analysis (OMA) method is conducted to obtain the experimental dynamic characteristics of the minaret and the initial FE model is calibrated by using the experimental results. Then, linear time history (LTH) and nonlinear time history (NLTH) analyses are carried out on the calibrated FE model by using two different ground motions. Iron clamps which used as connection element between the stones of the minaret considerably increase the tensile strength of the masonry system. The Concrete Damage Plasticity (CDP) model is selected in the nonlinear analyses in ABAQUS. The analyses conducted indicate that the results of the linear analyses are not as realistic as the nonlinear analysis results when compared with existing damage.
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    Effect of model calibration on seismic behaviour of a historical mosque
    Demir, A; Nohutcu, H; Ercan, E; Hokelekli, E; Altintas, G
    The objective of the study is to investigate the effects of model calibration on seismic behaviour of a historical mosque which is one of the most significant Ottomon structures. Seismic analyses of calibrated and noncalibrated numeric models were carried out by using acceleration records of Kocaeli earthquake in 1999. In numerical analysis, existing crack zones on real structure was investigated in detail. As a result of analyses, maximum stresses and displacements of calibrated and noncalibrated numerical models were compared each other. Consequently, seismic behaviour and damage state of historical masonry Hafsa Sultan mosque was determined as more realistic in the event of a severe earthquake.
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    A NEW STRONG FLOOR-REACTION WALL SYSTEM WITHOUT GALLERY FOR EXPERIMENTAL STUDIES IN STRUCTURAL MECHANICS
    Kaplan, H; Gönen, H; Nohutcu, H; Çetinkaya, N; Yilmaz, S
    Strong floors and reaction walls are important elements of structural mechanics laboratories. They should be designed before the construction of the laboratory building for efficiency. They have a gallery used for the anchorage of the test models and storage of test equipment. In this paper, a strong floor without a gallery has been designed for an existing laboratory facility. The anchorage system has been designed to fix the model structures to the strong floor. Design issues of strong floor and reaction floor systems are mentioned in the scope of the paper. The construction of the system is simple and economical and provides a comfortable environment for experimental studies.
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    Seismic Failure Pattern Prediction in a Historical Masonry Minaret under Different Earthquakes
    Nohutcu, H
    Historical structures are the values that are of great importance to that country, showing the roots of a country, and must be passed on from generation to generation. This study attempts to make a contribution to this goal. Seismic damage pattern estimation in a historical brick masonry minaret under different ground motion levels is investigated by using updated finite element models based on ambient vibration data in this study. Imaret Mosque which was built in 1481 AD is selected for an application. Surveying measurement and material tests were conducted to obtain a 3D solid model and mechanical properties of the components of the minaret. Firstly, the initial 3D finite element model of the minaret was analyzed and numerical dynamic characteristics of the minaret were obtained. Then, ambient vibration tests as well as operational modal analysis were implemented in order to obtain the experimental dynamic characteristics of the minaret. The initial finite element model of the minaret was updated by using the experimental dynamic results. Lastly, linear and nonlinear time-history analyses of the updated finite element model of the minaret were carried out using the acceleration records of two different level earthquakes that occurred in Turkey, in Afyon-Dinar (1995) and Cay-Sultanda (2002). A concrete damage plasticity model is considered in the nonlinear analyses. The conducted analyses indicate that the compressive and tension stress results of the linear analyses are not as realistic as the nonlinear analysis results. According to the nonlinear analysis, the Cay-Sultanda earthquake would inflict limited damage on the minaret, whereas the Dinar earthquake would damage some parts of the elements in the transition segment of the minaret.
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    Investigation of a historic masonry structure by numerical and operational modal analyses
    Nohutcu, H; Demir, A; Ercan, E; Hokelekli, E; Altintas, G
    This paper presents the results of model calibration conducted on a historical mosque called Hafsa Sultan in Manisa, Turkey. The finite element model of the mosque was calibrated by the use of the results obtained from ambient vibration tests of the structure. In order to develop a solid model of the structure, the dimensions of the structure, defects such as cracks and material degradations in the structure, and the materials used in different parts were identified. For the evaluation of the material properties of the structure, nondestructive and destructive testing methods were used. The numerical and experimental modal parameters of the structure were obtained by finite element method (FEM) and Operational Modal Analysis (OMA), respectively. The natural frequencies and corresponding mode shapes were obtained from both FEM and OMA and compared with each other. While a good compatibility was achieved between mode shapes, some differences between natural frequencies occurred. It was thought that the differences resulted from variations in the Young's modulus of masonry, cracks in elements or boundary conditions. Therefore, the finite element model was calibrated by changing material parameters. Finally, a more realistic numerical model of the mosque was put forward and the results were discussed in detail. Copyright (c) 2015 John Wiley & Sons, Ltd.
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    Seismic strengthening of pin-connected precast concrete structures with external shear walls and diaphragms
    Kaplan, H; Nohutcu, H; Cetinkaya, N; Yilmaz, S; Gönen, H; Atimtay, E
    Pin-connected precast concrete structures are widely used in some European countries of moderate seismicity. However, this structural system is not earthquake resistant because it does not have enough lateral stiffness or lateral-load resistance. Lack of a rigid diaphragm at the roof level imposes severe forces to connections. It is difficult to strengthen such buildings with conventional strengthening techniques because buildings must be unoccupied before retrofitting, which building owners do not like. To overcome this difficulty, employment of external shear walls and a diaphragm roof level are proposed in this study. A typical pin-connected precast concrete frame and a strengthened structure with the proposed method were tested under-imposed, reversed, cyclic drift of constant rate. The experimental study showed that the proposed method increased lateral stiffness, lateral-load resistance, and seismic energy dissipation and provided a diaphragm effect for the structure.
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    29 October 2007, Cameli earthquake and structural damages at unreinforced masonry buildings
    Kaplan, H; Yilmaz, S; Akyol, E; Sen, G; Tama, YS; Cetinkaya, N; Nohutcu, H; Binici, H; Atimtay, E; Sarisin, A
    A recent earthquake of M=4.9 occurred on 29 October 2007 in C, ameli, Denizli, which is located in a seismically active region at southwest Anatolia, Turkey. It has caused extensive damages at unreinforced masonry buildings like many other cases observed in Turkey during other previous earthquakes. Most of the damaged structures were non-engineered, seismically deficient, unreinforced masonry buildings. This paper presents a site survey of these damaged buildings. In addition to typical masonry damages, some infrequent, event-specific damages were also observed. Reasons for the relatively wide spread damages considering the magnitude of the event are discussed in the paper.