Sürdürülebilir Kalkınma Amaçları

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• MakaleYalnız künye2024/r/gumushane/14291
  Hysteretic behaviour of square-hollow-section T- and X-joints with in-plane bending moment

  Ozyurt, E.; Gunaydin, M.

  This study examined the hysteretic behaviour of Square Hollow Section (SHS) T- and X-joints subjected to cyclic in-plane bending moments. A nonlinear finite element software, Abaqus, was used to investigate SHS T- and X-joint seismic performance. Prior to the parametric study, the numerical model was validated based on the available test results in the literature. A comprehensive parametric study employed validated finite element models to evaluate the influence of critical geometric parameters, including the brace-to-chord width ratio (β) and the chord width-to-thickness ratio (γ). The results of the finite element analyses regarding ductility, flexural strength, and energy dissipation behaviour of SHS T- and X-joints under quasi-static cyclic in-plane bending were evaluated. Based on the hysteretic curves, increasing β generally leaded to higher initial stiffness and moment capacity in SHS joints, considerably reducing joint rotation. Conversely, the joints with larger γ exhibited reduced initial stiffness and moment capacity. Besides, the Eurocode 3 EN1993-1-8 predictions for the ultimate flexural strength of the joints are found to be conservative compared to finite element results. The results also revealed that the SHS T- and X-joints showed satisfactory ductility levels under in-plane bending load. It was observed that the SHS T- and X-joints with high β and low γ are advantageous for absorbing energy under seismic loads. These findings offered valuable insights for the seismic-resistant design of structures incorporating SHS joints, aiding in selecting optimal configurations based on specific performance requirements.

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• MakaleAçık Erişim2019/r/gumushane/16443
  Gastrointestinal and cutaneous anthrax: Case series

  Ozer, Vildan; Gunaydin, Mucahit; Pasli, Sinan; Aksoy, Firdevs; Gunduz, Abdulkadir

  Introduction: Anthrax is a zoonosis affecting herbivorous animals. Its agent is Bacillus anthracis and it is gram positive, aerobic or facultative anaerobic, immobile and has a capsule in the polypeptide structure. The incidence is gradually decreasing in the world and in our country. The disease is especially seen in areas where stock breeding is common. In this case series, 3 cases, one of them was mortal, took place after anthrax infected cow was eaten in February 2018 in Trabzon was shared. Case presentations: In the first case, as a result of the animal's meat was eaten, gastrointestinal anthrax and associated sepsis were seen. This patients blood culture was positive and she was died. Second case after contacting the patient who died, and third case after contacting the animal and eating its meat, diagnosed with cutaneous anthrax. Doxycycline treatment was started with cutaneous anthrax patients, these cases were recovered without any complications. Conclusion: We presented this article, to update our information about gastrointestinal anthrax and other anthrax types which are become a current issue again especially due to bioterrorism and also to keep it in mind in the differential diagnosis although it is rarely seen in our stock raising areas.

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• MakaleYalnız künye2018/r/gumushane/16182
  Automated Model Updating of Historical Masonry Structures Based on Ambient Vibration Measurements

  Altunisik, Ahmet Can; Okur, Fatih Yesevi; Genç, Ali Fuat; Günaydin, Murat; Adanur, Suleyman

  Finite-element (FE) model updating is a very effective procedure for determining the uncertainty parameters in a structural model and minimize differences between experimentally and analytically identified dynamic characteristics. This procedure can be practiced with manual and global/local automatic model updating procedures. Automatic model updating is very popular because of its applicability to all kinds of engineering structures to minimize differences, and its damage localization and structural health monitoring. This paper considers a historical masonry bastion to obtain its dynamic characteristics numerically with the finite-element method and experimentally with ambient vibration tests (AVTs). Sensitivity analyses for the uncertainty parameters and manual and automated model updating to minimize differences are also performed. A castle bastion located in Trabzon, Turkey is selected as an application. The FE model of structure is developed in commercial software. The first three natural frequencies are obtained between 5 and 10Hz, and AVTs are performed under natural excitation using enhanced frequency domain decomposition (EFDD) and subspace structural identification (SSI) techniques. The first three natural frequencies are obtained between 4 and 7Hz. The comparison of analytically and experimentally identified dynamic characteristics shows a close agreement between mode shapes, but 26% difference in natural frequencies. To minimize the difference, the FE model of the bastion is updated using manual and global/local automated updating, changing its material properties of Young's modulus and material density. The maximum differences are reduced from 27 to 3% with manual updating, and to 0.02% with automated model updating.

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• MakaleAçık Erişim2018/r/gumushane/18443
  Tarihi Bir Yığma Minarenin Onarım Sonrasındaki Dinamik Karakteristiklerinin Deneysel Olarak Belirlenmesi

  Günaydın, Murat

  Tarihi yapılar ülkemizin önemli kültür miraslarıdır. Bu yapılar; gerek geçmişi günümüze bağlamaları, gerek yapım tekniklerindeki yüksek mühendislik bilgisi, gerekse de bulundukları bölgelere sağladıkları ekonomik katkılardan dolayı oldukça önemli olup geleceğe bozulmadan aktarılmaları kaçınılmaz bir zorunluluktur. Bu yapıların varlıklarını sürdürebilmesi, yapısal davranışlarının belirlenmesi ve gerekli onarım ve/veya güçlendirme işlemlerin uygulanmasıyla mümkündür. Bu amaçla ülkemizdeki birçok tarihi yapı onarılmış ya da güçlendirilmiştir. Uygulanan onarım ve/veya güçlendirme işlemin yapının yapısal davranışına etkisi, yapının bu işlemlerden sonraki özgün halinin korunması kadar önemlidir. Dolayısıyla, uygulanan onarım ve/veya güçlendirme işleminin yapısal davranışına olan etkisi ayrıca incelenmelidir. Bu çalışmada, Trabzon İskenderpaşa Camii minaresinin onarım sonrasındaki dinamik karakteristikleri deneysel olarak belirlenmiştir. Dinamik karakteristiklerin elde edilmesinde Deneysel Modal Analiz Yöntemi kullanılmıştır. Elde edilen dinamik karakteristikler minarenin literatürde var olan onarım öncesi sonuçları ile karşılaştırılmış ve olası farklılıklar irdelenmiştir.

  İncele
• MakaleYalnız künye2018/r/gumushane/15863
  EFFECTS OF STRAND CONFIGURATION ON PRE-TENSIONED I-GIRDERS

  Atmaca, Barbaros; Ates, Sevket; Günaydin, Murat; Altunisik, Ahmet Can

  The purpose of this paper is to examine the effect of strand configuration on the behavior of precast, pre-tensioned concrete I-girders by considering design load components for highway bridges as dead loads and equivalent lane loads. Under these loads, bridge girder's bottom flange is exposed to tensile stresses. To minimize or eliminate the tensile stresses, compressive stresses are induced in pre-stressed concrete with strands. Determination of strand configuration is important as well as number of strands because it affects stress distribution and displacement of bridge girders. One of the typical precast I-girder with 90 cm height is considered in this study. To determine strand configuration effects, eighteen I-girders with the same cross-section, effective span length and material properties but different strand configuration are selected as an application. Equal prestressing force is applied all strands simultaneously. Three dimensional finite element (FE) models of girder are constituted using ANSYS software. Result of beam theory is used to verify the modeling techniques. At the end of the study, numerically identified stress distribution and displacement for I-girders compared with each other. It is seen that proper strand configuration is effective to reducing stresses and displacements of pre-stressed I-girder.

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• MakaleYalnız künye2018/r/gumushane/15218
  Ambient Vibration-Based System Identification of a Medieval Masonry Bastion for Health Assessment using Nonlinear Analyses

  Altunişik, Ahmet Can; Genç, Ali Fuat; Günaydin, Murat; Adanur, Süleyman; Yesevi Okur, Fatih

  Earthquakes have underlined the need for health monitoring and safety assessment of engineering structures in general and especially historical heritage. These structures can be exposed to many different loads such as earthquake and wind that may cause the deterioration and loss of structural integrity. In this study, ambient vibration-based system identification of Zaǧanos Bastion is carried out for health assessment using linear and nonlinear analyses. 3D finite element analyses of the bastion are performed using relievo drawings and analytical dynamic characteristics are obtained. Ambient vibration tests are conducted on the bastion and experimental dynamic characteristics such as natural frequencies, mode shapes and damping ratios are determined. Enhanced Frequency Domain Decomposition Method in the frequency domain and Stochastic Subspace Identification Method in the time domain are used to extract the experimental dynamic characteristics. Maximum differences are minimized using some uncertain parameters to obtain the updated finite element model. Linear and nonlinear time history analyses are carried out using 1999 Kocaeli earthquake ground motion record to display the maximum displacements, stresses and local damage regions with detail. This study suggests that minor damage at the connection points and exterior surface will sustain under destructive earthquakes.

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• MakaleAçık Erişim2018/r/gumushane/15075
  Sensitivity-Based Model Updating of Building Frames using Modal Test Data

  Altunişik, Ahmet Can; Karahasan, Olguhan Şevket; Genç, Ali Fuat; Okur, Fatih Yesevi; Günaydin, Murat; Adanur, Süleyman

  Model updating is of significant importance in the actual analyses of real structures. The differences between experimental and numerical dynamic characteristics can be minimized by means of this procedure. This procedure can be carried out using two approaches, namely, the manual model updating and the global or local automated model updating. The local model updating is a convenient tool for all kind of structures capable of minimizing the differences mentioned previously nearly to zero and also of identifying the damage locations and monitoring structural integrity. In this way, current realistic behavior of structures can be represented by updated finite element models. This paper describes a Reinforced Concrete (RC) frame model, its ambient vibration testing, finite element modeling and sensitivity-based automated model updating. The RC frame is of ½ geometric scale with two floors and two bays in the longitudinal direction. It was built and then subjected to ambient vibration tests to determine experimentally their dynamic characteristics. Additionally, the finite element computer program ANSYS was used to determine its initial numerical dynamic characteristics. The experimental and numerical results were compared resulting in maximum differences of 38.38% between them. To minimize these differences, the finite element model was updated using the global and local automated approach using a sensitivity-based analyses with some uncertain parameters. The differences were finally reduced to 4.4% and 0.21% by the global and the local automated model updatings, respectively. It is concluded that sensitivity-based automated updating is a very effective procedure to obtain the updated finite element model which can reflect the current behavior of a structure.

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  İncele
• MakaleYalnız künye2018/r/gumushane/13070
  Automated Model Updating Effect on the Linear and Nonlinear Dynamic Responses of Historical Masonry Structures

  Altunişik, A.C.; Okur, F.Y.; Genç, A.F.; Günaydin, M.; Karahasan, O.

  Finite element models supply the simulation of the problems to obtain the structural behaviors under different loading conditions. The updating processes based on changing the uncertain parameters such as material properties, boundary conditions, meshing size etc. are made to create actual finite element models in order to represent the real conditions of the problems. This procedure can be made using two methods, namely manual model updating and global/local automatic model updating. The global/local automatic model updating procedures are very popular owing to the applicability to all kind of engineering structures, minimizing the differences nearly to zero, availability of damage localization and structural health monitoring. In this paper a historical masonry armory building selected as an application and its finite element analyses, experimental measurements and automated model updating processes are carried out. The finite element model of the structures was developed with ANSYS software and first three natural frequencies are attained. The experimental dynamic characteristics such as natural frequencies, damping ratios and mode shapes are obtained using ambient vibration method. The differences between experimental and numerical frequencies are minimized up to the range of 0–1%, by using local updating procedure. The linear and nonlinear seismic analyses of the building are conducted on initial and updated models. At the end of the analyses, maximum displacements, principal stresses and strains are given with detail. In addition, crack distributions diagrams are attained to validate the stresses accumulation points. It can be seen that there is an increasing trend in the displacement, stress and strain values after finite element model updating both linear and nonlinear analysis. In addition, linear and nonlinear analysis results are compared with each other to evaluate the nonlinear analysis effect. It is concluded that the displacement and strain values are increased after nonlinear analysis. But, there is not any agreement in stress values.

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• MakaleYalnız künye2018/r/gumushane/11602
  Modal parameter identification of RC frame under undamaged, damaged, repaired and strengthened conditions

  Altunişik, Ahmet Can; Karahasan, Olguhan Şevket; Genç, Ali Fuat; Okur, Fatih Yesevi; Günaydin, Murat; Kalkan, Ebru; Adanur, Süleyman

  Structures are built on a design and then damaged in time by natural and manmade effects, repaired and strengthened for reusing. Determination of the structural behavior is very important to avoid future disaster. Operational Modal Analysis has been widely used recently to determine the inherent modal parameters of engineering structures and give significant information about the structural condition. Also, this method can be used to further studies such as model updating, damage detection and health monitoring. In this paper, it is aimed to investigate the changes of modal parameters considering undamaged, damaged, repaired and strengthened conditions using ambient vibration tests. For this purpose, a reinforced concrete frame model having two-floor with two spans in the longitudinal direction considering ½ geometric scales is built in laboratory. Four different cases are considered to emerge the efficiency of this procedure and the undamaged RC model is measured firstly to determine the initial modal parameters. Secondly, the lateral forces are applied to floor levels to obtain the damages, especially in beam-column joints. Thirdly, the damaged model is repaired using injection material and lastly strengthened with Carbon Fiber Reinforcement Polymer. It is also examined that what rate the dynamic characteristics return to back after repairing and strengthening studies by the comparison with undamaged condition? In addition to this the evaluation of carbon fiber reinforcement polymer effectiveness in strengthening for real applications is presented. It is seen that ambient vibration test is enough to identify the modal parameters of engineering structures for different conditions. The modal parameters are decreased distinctly with damages, and reverted almost initial condition with strengthening.

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• MakaleYalnız künye2018/r/gumushane/11368
  Dynamic response of a historical armory building using the finite element model validated by the ambient vibration test

  Altunişik, Ahmet Can; Genç, Ali Fuat; Günaydin, Murat; Okur, Fatih Yesevi; Karahasan, Olguhan Şevket

  In this paper, the aim was to determine the nonlinear dynamic response of historical masonry armory buildings using a validated finite element model. Eight ambient vibration tests were conducted on the building, using three different measurement test setups to extract the dynamic characteristics using the Enhanced Frequency Domain Decomposition method. A finite element model was constructed in ANSYS and the dynamic characteristics were obtained numerically. It can be seen that there is a good correlation between the mode shapes, but there are differences in natural frequencies with maximum values of 10.1%, 7.4% and 13.4% for first the three modes. To determine the nonlinear dynamic response, the validated finite element model was analyzed using the Kocaeli earthquake motion. The Drucker–Prager criterion and Willam–Warnke surface were considered for the nonlinear material models. At the end of the analyses, maximum displacements, principal stresses and strains are given in detail using contour diagrams. It is evident that the displacements show an increasing trend from the base to the top point of the building. Stresses occurred on the corners, openings and transition segments. In addition, crack distribution diagrams were drawn up to illustrate the stress accumulation points.

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