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- MakaleYalnız künye2018Scopus SJRQ3Automated 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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İncele - MakaleYalnız künye2017Scopus SJRQ2Finite 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.
AtıfWoS12OpenAlex11İncele - MakaleYalnız künye2012Scopus SJRQ2Determination of water level effects on the dynamic characteristics of a prototype arch dam model using ambient vibration testing
Sevim, B.; Bayraktar, A.; Altunişik, A.C.; Adanur, S.; Akköse, M.
This study investigated the water level effects on the dynamic characteristics of a prototype arch dam model using ambient vibration testing were investigated. Achievement of this purpose involved construction of a prototype arch dam-reservoir-foundation model under laboratory. The dam body was constructed with 60 cm height. Ambient vibration tests on the arch dam estimated its natural frequencies, mode shapes and damping ratios for different water levels. In the ambient vibration tests, ambient excitations are provided from small impact effects and the responses of the arch dam are measured. It can be stated from the study that natural frequencies are not overly changed among 0-30 cm water levels; however they are increased for higher water levels. The difference between the first natural frequencies of the arch dam obtained from empty reservoir (H = 0 cm) and full reservoir (H = 60 cm) is about 20-25%.
AtıfScopus24WoS21OpenAlex29İncele - MakaleYalnız künye2011Scopus SJRQ1Finite element model calibration effects on the earthquake response of masonry arch bridges
Sevim, Baris; Bayraktar, Alemdar; Altunisik, Ahmet Can; Atamtürktür, Sezer; Birinci, Fatma
The focus of this paper is to illustrate the importance of model calibration and in situ vibration testing by comparing the finite element model predictions of the earthquake response of the two historical arch bridges, Osmanli and Senyuva, before and after model calibration. The three-dimensional finite element models of these two arch bridges, built in the ANSYS finite element program, are used to predict bridge dynamic characteristics, such as natural frequencies and mode shapes. Following the analytical study, ambient vibration tests were conducted to experimentally obtain dynamic characteristics of these two bridges. During ambient vibration tests, accelerometers were placed at several points on the bridge to collect the vibration response due to natural and operational excitation sources. Enhanced frequency domain decomposition and stochastic subspace identification techniques were used to extract the experimental natural frequencies, mode shapes and damping ratios. Finite element models of the two arch bridges were adjusted such that the model predictions reproduce the ambient vibration test results with increased fidelity. The behavior of the masonry arch bridges under earthquake excitation recorded during the Erzincan Earthquake in 1992 is simulated by both the initial and adjusted finite element models. The findings of this study emphasize the importance of model calibration and ambient vibration testing. (C) 2010 Elsevier B.V. All rights reserved.
AtıfWoS69OpenAlex84İncele - MakaleYalnız künye2011Scopus SJRQ1Finite element model updating effects on nonlinear seismic response of arch dam-reservoir-foundation systems
Bayraktar, Alemdar; Sevim, Baris; Altunisik, Ahmet Can
This paper investigates the effects of finite element model updating on nonlinear seismic response of arch dam-reservoir-foundation systems. The highest arch dam in Turkey named Berke is selected for the numerical and experimental applications. Firstly, 3D finite element model of Berke Dam was constituted using an ANSYS software. In the analytical modeling, arch dam-reservoir-foundation interaction is represented by Lagrangian approach. Then ambient vibration tests were conducted to dam for four days, and experimental dynamic characteristics were estimated using an Enhanced Frequency Domain Decomposition technique. Experimental characteristics are compared with those of analytical obtained by the linear finite element analysis of the coupled system. Good agreement between mode shapes is observed during this comparison, though natural frequencies disagree by 15-20%. The linear finite element model of Berke Dam was updated by adjusting the material properties of the dam and foundation. By introducing the Drucker-Prager damage criterion, the updated linear finite element model was extended into an onlinear model. Nonlinear seismic behavior of Berke Dam was determined considering the acceleration record of Adana-Ceyhan, Turkey, earthquake in 1998 that occurred near the arch dam region. It is highlighted that the finite element model updating provides a significant influence on the nonlinear seismic response of arch dams. (C) 2010 Elsevier B.V. All rights reserved.
AtıfWoS50OpenAlex62İncele - MakaleYalnız künye2011Scopus SJRQ1Assessment of nonlinear seismic performance of a restored historical arch bridge using ambient vibrations
Sevim, Bariş; Bayraktar, Alemdar; Altunişik, Ahmet Can; Atamtürktür, Sezer; Birinci, Fatma
Historic masonry arch bridges are vital components of transportation systems in many countries worldwide, ensuring the ready access of goods and services to millions of people. The structural failure of these historic structures would severely and adversely impact the economies of these nations due to the massive disruptions of transportation systems accompanying such failures. To successfully maintain these aging masonry structures, performance assessment must incorporate the unique mechanical characteristics of masonry. Therefore, the preferred analysis technique must go beyond a linear approach. This study assesses the earthquake performance of a restored historical masonry arch bridge through nonlinear finite element analysis incorporating the Drucker-Prager damage criterion. The case study structure is the Mikron Arch Bridge, a nineteenth century Ottoman Era structure built over the Firtina River near Rize, Turkey, and restored in 1998. The Mikron Arch Bridge was first subjected to ambient vibration testing, during which accelerometers were placed at several points on the bridge span to record the bridge vibratory response. The investigators then used Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques to extract the experimental natural frequencies, mode shapes, and damping ratios from these measurements. Experimental results were compared with those obtained by the linear finite element analysis of the bridge. Good agreement between mode shapes was observed during this comparison, though natural frequencies disagree by 8-10%. The boundary conditions of the linear finite element model of Mikron Arch Bridge are adjusted such that the analytical predictions agree with the ambient vibration test results. By introducing the Drucker-Prager damage criterion, the calibrated linear FE model was next extended into a nonlinear model. Nonlinear analysis of seismic behavior of Mikron arch bridge was performed considering the acceleration record of Erzincan earthquake in 1992 that occurred near the Mikron Bridge region. The displacement and stress results were observed to be allowable level of the stone material. Moreover, linear FE model calibrations elicited a significant influence on the nonlinear FE model simulations.
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