Sürdürülebilir Kalkınma Amaçları

• 14
• 4
• 1

• MakaleYalnız künye2017/r/gumushane/16376
  Finite Modeling Updating Effects on the Dynamic Response of Building Models

  Günaydin, M.; Adanur, S.; Altunisik, A. C.; Sevim, B.; Bayraktar, A.

  An improved finite element model was used to obtain more accurate modeling of engineering structures. The main goal of this paper was to determine how this improved modeling procedure affects the dynamic response of buildings based on experimental modal parameters such as natural frequencies, mode shapes and damping ratios. For experimental assessment, three small, one-story, two-bay, reinforced concrete buildings with raft foundation were constructed under laboratory conditions. The initial three-dimensional finite element models, built with the ANSYS software, were used to analytically identify modal parameters, including natural frequencies and mode shapes. Following the analytical study, the ambient vibration tests were performed to obtain modal parameters, experimentally. The enhanced frequency domain decomposition method and the stochastic subspace identification method were used to identify the modal parameter. The analytical and experimental modal parameters were compared and then initial finite element models were updated to minimize the differences by changing of some uncertain parameters such as materials properties. With model updating, the maximum difference between the measured and initially obtained frequency was reduced from 28.47 to 4.88%. To show the model updating effect on dynamic response of building models, dynamic analysis with the experimental computed damping ratios and 5% damping ratio were carried out using 1992 Erzincan earthquake ground motion record. For the experimental damping ratios, the maximum differences in the displacements and stresses between the initial and updated models were obtained as 23 and 32%, respectively. These differences were calculated as 43 and 15 % for the 5 % damping ratio. Comparisons of dynamic analyses results for the initial and updated model show that the finite element model updating affects the dynamic response of the buildings considerably.

  İncele
• MakaleYalnız künye2017/r/gumushane/15232
  System identification of arch dam model strengthened with CFRP composite materials

  Altunisik, A.C.; Gunaydin, M.; Sevim, B.; Adanur, S.

  This paper presents the structural identification of an arch dam model for the damaged, repaired and strengthened conditions under different water levels. For this aim, an arch dam-reservoir-foundation model has been constructed. Ambient vibration tests have been performed on the damaged, repaired and strengthened dam models for the empty reservoir (0 cm), 10 cm, 20 cm, 30 cm, 40 cm, 50 cm and full reservoir (60 cm) water levels to illustrate the effects of water levels on the dynamics characteristics. Enhanced Frequency Domain Decomposition Method in the frequency domain has been used to extract the dynamic characteristics. The dynamic characteristics obtained from the damaged, repaired and strengthened dam models show that the natural frequencies and damping ratios are considerably affected from the varying water level. The maximum differences between the frequencies for the empty and full reservoir are obtained as 16%, 33%, and 25% for damaged, repaired and strengthened model respectively. Mode shapes obtained from the all models are not affected by the increasing water level. Also, after the repairing and strengthening implementations, the natural frequencies of the arch dam model increase significantly. After strengthening, between 46-92% and 43-62% recovery in the frequencies are calculated for empty and full reservoir respectively. Apparently, after strengthening implementation, the mode shapes obtained are more acceptable and distinctive compared to those for the damaged model.

  • 
  İncele
• MakaleYalnız künye2016/r/gumushane/16368
  Dynamic Characteristics of an Arch Dam Model before and after Strengthening with Consideration of Reservoir Water

  Altunisik, Ahmet Can; Günaydin, Murat; Sevim, Baris; Bayraktar, Alemdar; Adanur, Suleyman

  This technical note presents an investigation about the changing of dynamic characteristics of an arch dam model before and after strengthening considering reservoir water. To this end, an arch dam-reservoir-foundation model has been constructed in the laboratory. Ambient vibration tests have been performed on the damaged and strengthened arch dam models for empty and full reservoir to determine the effect of water on the dynamics characteristics. Enhanced frequency domain decomposition method has been used to extract the dynamic characteristics. Finally, the dynamic characteristics obtained from the damaged and strengthened dam models have been compared to with each other. Also, the natural frequencies for damaged and strengthened models are compared to detect the effect of strengthening application on the frequencies. Results indicate that the natural frequencies and damping ratios are changed with the full reservoir. However, mode shapes are not changed. Results also show that the natural frequencies of damaged dam considerably increase after strengthening applications.

  • 
  İncele
• MakaleYalnız künye2016/r/gumushane/16377
  Retrofitting Effect on the Dynamic Properties of Model-Arch Dam with and without Reservoir Water Using Ambient-Vibration Test Methods

  Altunisik, Ahmet Can; Günaydin, Murat; Sevim, Baris; Bayraktar, Alemdar; Adanur, Suleyman

  Continuous health monitoring and regular condition assessment is of vital importance for engineering structures in general and especially for arch dams. These structures can be exposed to many different loads such as earthquake, blast, wind, ice, and water pressure, which may cause deterioration and loss of structural integrity. Such development may have severe economic consequence and, more importantly, may present a serious risk to public safety. Therefore, the structural behavior of arch dams must be monitored at regular intervals during their service life, although the overall failure rate of these dams is around 1%. Experimental measurements by ambient vibration test methods are among the most commonly preferred inspection techniques for the evaluation of structural performance and safety. The aim of this research is to examine the retrofitting effect on the dynamic properties of a damaged arch dam model, with and without reservoir water, after retrofitting with high-strength structural repair mortar and carbon fiber reinforced polymer composite material. To this end, an arch dam-reservoir-foundation model was built. In the study, ambient vibration tests were carried out for three test-cases to determine changes in dynamic properties, such as natural frequency, mode shape, and damping ratio before and after retrofitting. The three cases were (1)a severely damaged dam with full reservoir (Case-A), (2)a repaired dam with full reservoir (Case-B), and (3)a strengthened dam with full reservoir (Case-C). In addition, all the measurement tests were repeated with an empty reservoir to extract the effect of water. Data for the ambient vibration tests were gathered from the dam body during vibrations by natural excitations. These excitations were provided through small impacts, and the response signals were measured by sensitivity accelerometers placed at the crest points. To obtain the experimental dynamic properties, the enhanced frequency domain decomposition method in the frequency domain was used. Comparisons of experimentally identified dynamic properties for the damaged and the retrofitted dam showed that the retrofitting application affected the structural behavior of the arch dam considerably. It was very effective in restoring the structure's original dynamic properties.

  • 
  İncele
• MakaleAçık Erişim2015/r/gumushane/15779
  Time dependent changing of dynamic characteristics of laboratory arch dam model

  Altunişik, Ahmet Can; Sevİm, Barış; Bayraktar, Alemdar; Adanur, Süleyman; Günaydin, Murat

  This paper investigates the time dependent changing of dynamic characteristics of laboratory arch dam models using ambient vibration test. For this aim, a prototype arch dam-reservoir-foundation model is constructed in laboratory conditions. The first experimental measurement tests are performed after the poured concrete aged for 10 months for some damage scenarios such as undamaged, minor-damaged and severely damaged of dam body in November 2009. To extract the experimental dynamic characteristics such as natural frequencies, mode shapes and damping ratios, a small impact effect is used as a source of ambient vibrations. Experimental measurements tests are repeated using same excitations considering severely damaged conditions with and without reservoir water in February 2014, and the dynamic characteristics are obtained, experimentally. Enhanced Frequency Domain Decomposition Method in the frequency domain is used to extract the experimental dynamic characteristics. At the end of the study, experimentally identified dynamic characteristics are compared with each other and time effects are investigated in detail. Maximum differences between the natural frequencies obtained as 15.36% and 14.38% in the third mode for empty and full reservoir conditions, respectively. It is thought that the increase of the natural frequencies is resulted from gaining of rigidity of the concrete, ageing, temperature and different environmental effects.

  İncele
• MakaleYalnız künye2015/r/gumushane/15579
  CFRP composite retrofitting effect on the dynamic characteristics of arch dams

  Altunişik, Ahmet Can; Günaydin, Murat; Sevim, Bariş; Bayraktar, Alemdar; Adanur, Süleyman

  The purpose of this study is to investigate the effect of retrofitting dynamic characteristics of a damaged laboratory arch dam model, subsequently repaired with high-strength structural mortar and strengthened with composite carbon fiber reinforced polymer. This study constructed in laboratory conditions is a prototype arch dam-reservoir-foundation model. Five test cases of ambient vibration on the arch dam model illustrate the changes in dynamic characteristics: natural frequency, mode shape, and damping ratio, before and after retrofitting. The ambient vibration tests collected data from the dam body during vibrations by natural excitations which provided small impacts and response signals from sensitivity accelerometers placed at crest points. Enhanced Frequency Domain Decomposition Method in the frequency domain extracts the experimental dynamic characteristics. At the end of the study, experimentally identified dynamic characteristics obtained from all test cases have been compared with each other. Apparently, after the retrofitting, the natural frequencies of the dam body increased considerably, demonstrating that the retrofitting, including repairing and strengthening is very effective on the flashback of initial dynamic characteristics.

  • 
  İncele
• MakaleAçık Erişim2015/r/gumushane/15493
  Static and dynamic responses of Halgavor footbridge using steel and FRP materials

  Gunaydin, M.; Adanur, S.; Altunisik, A.C.; Sevim, B.

  In recent years, the use of fiber reinforced polymer composites has increased because of their unique features. They have been used widely in the aircraft and space industries, medical and sporting goods and automotive industries. Thanks to their beneficial and various advantages over traditional materials such as high strength, high rigidity, low weight, corrosion resistance, low maintenance cost, aesthetic appearance and easy demountable or moveable construction. In this paper, it is aimed to determine and compare the geometrically nonlinear static and dynamic analysis results of footbridges using steel and glass fiber reinforced polymer composite (GFRP) materials. For this purpose, Halgavor suspension footbridge is selected as numerical examples. The analyses are performed using three identical footbridges, first constructed from steel, second built only with GFRP material and third made of steel-GFRP material, under static and dynamic loadings using finite element method. In the finite element modeling and analyses, SAP2000 program is used. Geometric nonlinearities are taken into consideration in the analysis using P-Delta criterion. The numerical results have indicated that the responses of the three bridges are different and that the response values obtained for the GFRP composite bridge are quite less compared to the steel bridge. It is understood that GFRP material is more useful than the steel for the footbridges.

  • 
  İncele
• MakaleYalnız künye2014/r/gumushane/15511
  Determination of structural behavior of Bosporus suspension bridge considering construction stages and different soil conditions

  Günaydin, Murat; Adanur, Süleyman; Altunişik, Ahmet Can; Sevim, Bariş; Türker, Emel

  In this paper, it is aimed to determine the structural behavior of suspension bridges considering construction stages and different soil conditions. Bosporus Suspension Bridge connecting the Europe and Asia in Istanbul is selected as an example. Finite element model of the bridge is constituted using SAP2000 program considering existing drawings. Geometric nonlinearities are taken into consideration in the analysis using P-Delta large displacement criterion. The time dependent material strength of steel and concrete and geometric variations is included in the analysis. Time dependent material properties are considered as compressive strength, aging, shrinkage and creep for concrete, and relaxation for steel. To emphases the soil condition effect on the structural behavior of suspension bridges, each of hard, medium and soft soils are considered in the analysis. The structural behavior of the bridge at different construction stages and different soil conditions has been examined. Two different finite element analyses with and without construction stages are carried out and results are compared with each other. At the end of the analyses, variation of the displacement and internal forces such as bending moment, axial forces and shear forces for bridge deck and towers are given in detail. Also, displacement and stresses for bridge foundation are given with detail. It can be seen from the analyses that there are some differences between both analyses (with and without construction stages) and the results obtained from the construction stages are bigger. It can be stated that the analysis without construction stages cannot give the reliable solutions. In addition, soil condition have effect on the structural behavior of the bridge. So, it is thought that construction stage analysis using time dependent material properties, geometric nonlinearity and soil conditions effects should be considered in order to obtain more realistic structural behavior of suspension bridges.

  • 
  İncele
• MakaleYalnız künye2012/r/gumushane/16178
  Seismic Performance Assessment of Masonry Tile Domes through Nonlinear Finite-Element Analysis

  Atamturktur, S.; Sevim, B.

  This article discusses a combined analytical and experimental study on the nonlinear seismic performance of two Guastavino-style masonry domes located in the United States. The seismic performance of these masonry domes is simulated with nonlinear finite-element (FE) models. To support the assumptions and decisions established during the development of the FE models, the vibration response of the domes is measured on-site and systematically compared against the numerical model predictions. Linear FE models are developed that are in close agreement with the measured natural frequencies and in visual agreement with the measured mode shapes. Next, these linear models are extended into the nonlinear range by incorporating the Drucker-Prager damage criterion. Finally, nonlinear FE models are used to assess the performance of these two domes under seismic loadings obtained from the 1940 El Centro earthquake acceleration records. The predicted displacements and internal tensile stress levels are used to make inferences about the potential behavior of these two buildings under the selected earthquake load. DOI: 10.1061/(ASCE)CF.1943-5509.0000243. (C) 2012 American Society of Civil Engineers.

  İncele
• MakaleYalnız künye2012/r/gumushane/16401
  Construction stage analysis of fatih sultan mehmet suspension bridge

  Günaydin, Murat; Adanur, Suleyman; Altunisik, Ahmet Can; Sevim, Baris

  In this study, it is aim to perform the construction stage analysis of suspension bridges using time dependent material properties. Fatih Sultan Mehmet Suspension Bridge connecting the Europe and Asia in Istanbul is selected as an example. Finite element models of the bridge are modelled using SAP2000 program considering project drawing. Geometric nonlinearities are taken into consideration in the analysis using P-Delta large displacement criterion. The time dependent material strength variations and geometric variations are included in the analysis. Because of the fact that the bridge has steel structural system, only prestressing steel relaxation is considered as time dependent material properties. The structural behaviour of the bridge at different construction stages has been examined. Two different finite element analyses with and without construction stages are carried out and results are compared with each other. As analyses result, variation of the displacement and internal forces such as bending moment, axial forces and shear forces for bridge deck and towers are given with detail. It is seen that construction stage analysis has remarkable effect on the structural behaviour of the bridge.

  İncele