Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleYalnız künye2018Ambient 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.
- MakaleAçık Erişim2018Sensitivity-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.
- MakaleYalnız künye2018Modal 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.
- MakaleYalnız künye2016Non-destructive testing of an ancient Masonry Bastion
Altunişik, Ahmet Can; Adanur, Süleyman; Genç, Ali Fuat; Günaydin, Murat; Okur, Fatih Yesevi
Historical masonry structures have seismic vulnerability and most damages and demolishes arise from the seismic actions like earthquakes. In this paper, the structural behavior of Zağanos Bastion is examined with experimental and numerical methods. The operational modal analysis technique is used to illustrate the dynamic characteristics of the bastion experimentally. Finite element model is developed by ANSYS software and dynamic characteristics of the bastion, such as natural frequencies and mode shapes are calculated numerically. Furthermore, time history seismic analysis is carried out. The results show that the ambient vibration measurements are enough to identify the structural response of the bastion. Maximum differences between the natural frequencies are attained as 26%. To minimize these differences, finite element model of the bastion should be updated by using some uncertain parameters. The principal stresses are satisfied in general, but the maximum tensile and compression stresses values exceed the allowable code limits at some points of the masonry components.
- MakaleAçık Erişim2015Time 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.
- MakaleYalnız künye2015CFRP 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.
- MakaleYalnız künye2015Dynamic responses of industrial reinforced concrete chimneys strengthened with fiber-reinforced polymers
Karaca, Zeki; Türkeli, Erdem; Günaydin, Murat; Adanur, Süleyman
Industrial reinforced concrete (RC) chimneys are tall and slender structures that need repair and strengthening in their service lives. Fiber-reinforced polymers (FRPs) are continuously becoming a popular material that is used for strengthening purposes of RC structures. The purpose of this study is to determine the effect of FRP strengthening on dynamic responses of industrial RC chimneys. A 75-m-high industrial RC chimney with an opening on the body was selected for FRP strengthening. First, three-dimensional finite element model of the chimney and its modal analyses were performed in ANSYS software. Then, linear transient analyses of the chimney were carried out by using 1992 Erzincan Earthquake ground motion record. After that, body of chimney was strengthened with FRP composite, and dynamic analyses were performed. Finally, dynamic responses of chimney before and after FRP strengthening, such as displacements and maximum-minimum principal stresses, were compared. At the end of the study, it was seen that displacements increased along the height of the chimney, maximum and minimum principal stresses occurred at the region of opening and base for all analysis, respectively. Also, it was seen from this study that FRP strengthening is effective on the dynamic response of industrial RC chimneys.
- MakaleYalnız künye2014Determination 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.
- MakaleAçık Erişim2012Construction stage analysis of Humber Suspension Bridge
Adanur, Süleyman; Günaydin, Murat; Altunişik, Ahmet Can; Sevim, Bariş
Suspension bridges are widely used as engineering structures to across long spans and give rise to the usage of domains under the bridge. In the finite element analyses of suspension bridges, it is assumed that the structure is built and loaded in a second. However, this type of analysis does not always give the reliable and healthy solutions. Because, construction period of this type of the structures continue along time and loads may be changed during this period. Therefore, construction stages and time dependent material properties should be considered in the analysis to obtain the reliable and healthy results. This paper presents the construction stage analysis of suspension bridges using time dependent material properties. For this purpose, Humber Suspension Bridge built near Kingston upon Hull, England is chosen as an example. Finite element model of the bridge is constituted using SAP2000 program considering project 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 are included in the analysis. Time dependent material properties are considered as compressive strength, aging, shrinkage and creep for concrete, and relaxation for steel. The structural response 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 can be seen from the study that there are some differences between both analyses (with and without construction stages) and the results obtained from the construction stages are bigger. So, it is thought that construction stage analysis using time dependent material properties and geometric nonlinearity should be considered in order to obtain more realistic structural response of suspension bridges.
- MakaleYalnız künye2010Finite element model updating of an arch type steel laboratory bridge model using semi-rigid connection
Altunişik, Ahmet Can; Bayraktar, Alemdar; Sevlm, Bariş; Kartal, Murat Emre; Adanur, Süleyman
This paper presents finite element analyses, experimental measurements and finite element model updating of an arch type steel laboratory bridge model using semi-rigid connections. The laboratory bridge model is a single span and fixed base structure with a length of 6.1 m and width of 1.1m. The height of the bridge column is 0.85 m and the maximum arch height is 0.95 m. Firstly, a finite element model of the bridge is created in SAP2000 program and analytical dynamic characteristics such as natural frequencies and mode shapes are determined. Then, experimental measurements using ambient vibration tests are performed and dynamic characteristics (natural frequencies, mode shapes and damping ratios) are obtained. Ambient vibration tests are performed under natural excitations such as wind and small impact effects. The Enhanced Frequency Domain Decomposition method in the frequency domain and the Stochastic Subspace Identification method in the time domain are used to extract the dynamic characteristics. Then the finite element model of the bridge is updated using linear elastic rotational springs in the supports and structural element connections to minimize the differences between analytically and experimentally estimated dynamic characteristics. At the end of the study, maximum differences in the natural frequencies are reduced on average from 47% to 2.6%. It is seen that there is a good agreement between analytical and experimental results after finite element model updating. Also, connection percentages of the all structural elements to joints are determined depending on the rotational spring stiffness.
- MakaleYalnız künye2010Stochastic finite element analysis of long-span bridges with CFRP cables under earthquake ground motion
Çavdar, Özlem; Bayraktar, Alemdar; Adanur, Süleyman; Başaǧa, Hasan Basri
Stochastic seismic analysis of long-span bridges with Carbon fibre reinforced polymer (CFRP) cables are presented in this study through combination of the advantages of the perturbation based stochastic finite element method (SFEM) and Monte Carlo simulation (MCS) method. Jindo cable-stayed and Fatih Sultan Mehmet (Second Bosporus) suspension bridges are chosen as an example. Carbon fibre reinforced polymer cable (CFRP) and steel cables are used separately, in which the cable's cross sectional area is determined by the principle equivalent axial stiffness. Geometric nonlinear effects are considered in the analysis. Uncertainties in the material are taken into account and Kocaeli earthquake in 1999 is chosen as a ground motion. The efficiency and accuracy of the proposed algorithm are validated by comparing with results of MCS method. It can be stated that using of CFRP cables in long-span bridges subjected to earthquake forces is feasible.
- MakaleYalnız künye2010Stochastic finite element analysis of a cable-stayed bridge system with varying material properties
Çavdar, Özlem; Bayraktar, Alemdar; Adanur, Süleyman
Stochastic seismic finite element analysis of a cable-stayed bridge whose material properties are described by random fields is presented in this paper. The stochastic perturbation technique and Monte Carlo simulation (MCS) method are used in the analyses. A summary of MCS and perturbation based stochastic finite element dynamic analysis formulation of structural system is given. The Jindo Bridge, constructed in South Korea, is chosen as a numerical example. The Kocaeli earthquake in 1999 is considered as a ground motion. During the stochastic analysis, displacements and internal forces of the considered bridge are obtained from perturbation based stochastic finite element method (SFEM) and MCS method by changing elastic modulus and mass density as random variable. The efficiency and accuracy of the proposed SFEM algorithm are evaluated by comparison with results of MCS method. The results imply that perturbation based SFEM method gives close results to MCS method and it can be used instead of MCS method, especially, if computational cost is taken into consideration.