Browsing by Author "Hökelekli E."
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Item Investigation of seismic safety of a masonry minaret using its dynamic characteristics(Techno Press, 2016) Başaran H.; Demir A.; Ercan E.; Nohutçu H.; Hökelekli E.; Kozanoğlu C.Besides their spiritual significance, minarets are humanity's cultural heritage to the future generations due to their historical and architectural attraction. Currently, many historical masonry minarets are damaged and destroyed due to several reasons such as earthquakes and wind. Therefore, safety of these religiously significant buildings needs to be thoroughly investigated. The utmost care must be taken into account while investigating these structures. Our study investigated earthquake behavior of historical masonry minaret of Haci Mahmut Mosque. Destructive and non-destructive tests were carried out to determine earthquake safety of this structure. Brick-stone masonry material properties of structure were determined by accomplishing ultrasonic wave velocity, Schmidt Hammer, uniaxial compression (UAC) and indirect tension (Brazilian) tests. Determined material properties were used in the finite element analysis of the structure. To validate the numerical analysis, Operational Modal Analysis was applied to the structure and dynamic characteristics of the structure were determined. To this end, accelerometers were placed on the structure and vibrations due to environmental effects were followed. Finite element model of the minaret was updated using dynamic characteristics of the structure and the realistic numerical model of the structure was obtained. This numerical model was solved by using earthquake records of Turkey with time history analysis (THA) and the realistic earthquake behavior of the structure was introduced. © 2016 Techno-Press, Ltd.Item Finite element model updating of a historical minaret via operational modal analysis(International Operational Modal Analysis Conference (IOMAC), 2017) Ercan E.; Hökelekli E.; Demir A.; Nohutçu H.Finite element method is commonly used for analysis of historical structures. However, since material properties of historical structures are evaluated from destructive tests using empirical formulas, this approach makes the results of finite element analysis questionable. In recent years Operational Modal Analysis of historical masonry structures have found great interest because by the help of Operational Modal Analysis, the material parameters and the boundary conditions can be verified and the finite element model can be updated. The updated model is a more realistic model of the historical structures and gives more accurate results. This study describes the results of a model updating study conducted on a historical minaret. For the purposes of developing a 3-D solid model of the minaret; the dimensions, defects and material degradations in the minaret were determined in detail by making a measurement survey. For evaluation of the material properties of the minaret, nondestructive and destructive testing methods were applied. The modal analysis of the structure was done by FEM. Then, Operational Modal Analysis was carried out and dynamic properties were extracted. The results obtained from ambient vibration measurements of the minaret were used to update the finite element model of the minaret. The natural frequencies and corresponding mode shapes were determined from both theoretical and experimental modal analyses and compared with each other. A good harmony was attained between mode shapes, but differences between natural frequencies were observed. Model updating was realized via changing material parameters and boundary conditions. Finally, the more realistic finite element model of the minaret was put forward and the results were discussed.Item Seismic assessment in a historical masonry minaret by linear and non-linear seismic analyses(Budapest University of Technology and Economics, 2020) Hökelekli E.; Demir A.; Ercan E.; Nohutçu H.; Karabulut A.Operational Modal Analysis (OMA) method is frequently used in order to determine dynamical properties of historical masonry structures. In this study, damage pattern of historical Alaca minaret which is selected as application is investigated under different ground motions by updating finite element models (FEM) depending on operational modal analysis test. Initial Finite element model was prepared in ABAQUS V10 program and numerical dynamic characteristics of minaret were determined. In addition, experimental dynamic properties of minaret were provided by operational modal analysis. Initial numerical model of brick masonry structure was calibrated via OMA method. Then, linear and non-linear seismic analyses of calibrated FEM of historical minaret were performed by using different earthquakes acceleration records that occurred in Turkey. Concrete Damage Plasticity model was taken into account in non-linear seismic analyses. As a result of the analyses, it is concluded that the stresses obtained with linear analyses aren’t as realistic as the non-linear analyses results and the earthquakes can cause some damages in the minaret. © 2020, Budapest University of Technology and Economics. All rights reserved.Item The behavior of concrete-encased steel composite column-beam joints under cyclic loading(John Wiley and Sons Ltd, 2021) Şermet F.; Ercan E.; Hökelekli E.; Demir A.; Arısoy B.This study outlines the cyclic loading response of a concrete-encased steel profile composite column-reinforced concrete beam connection. The experimental study performed for an interior joint. The column in joint was designed as a concrete-encased I-steel profile composite column according to Eurocode 4, and the beam was designed as a regular reinforced concrete beam according to local building codes. In order to emphasize the effect of the joint design, different steel core orientations were used. The numerical analysis was performed using ABAQUS to predict behavior of the joint. The performance of the samples compared the load-carrying capacity, ductility, and failure type. Comparisons were made using load–displacement relationships and failure mechanisms. The analysis results showed that the failure was determined by the behavior of the beam, and the joint capacity depended on the shear capacity of the beam. © 2021 John Wiley & Sons, Ltd.Item The effect of the gravity on the earthquake performance of roller compacted concrete dams(Tulpar Academic Publishing, 2024) Şermet F.; Kartal M.E.; Yiğit M.E.; Hökelekli E.Roller compacted concrete (RCC) is a dry concrete mixture often utilized in the construction of large dams. The interlayer of the RCC dam, which is the weakest plane of the structure, can easily fail under hydraulic shear load, geological impact, earthquake force and environmental impact. In this study linear and performance analyzes were carried out for eight different scenarios for foundation effect, gravity effect and empty and full reservoir situations. In analyses, the earthquake response and performance of the Akçakoca RCC Dam, taking into account the interaction between the dam and the water. The reservoir water behavior is simulated using the Eulerian-Lagrangian coupled (CEL) approach with finite elements modeling. Linear analyses reveal that hydrodynamic pressure leads to increased displacements and principal stresses. The earthquake performance evaluation of the Akçakoca RCC dam indicates that critical concrete damages are expected based on linear time-history analyses conducted for both empty and full reservoir scenarios. Besides, according to this study, gravity effect clearly increases the earthquake performance of the dam. © 2024 by the Authors.