Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleYalnız künye2017Finite 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.
- MakaleYalnız künye2012Determination 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%.
- MakaleYalnız künye2011Dynamic Characteristics of a Prototype Arch Dam
Sevim, B.; Bayraktar, A.; Altunışık, A.C.; Adanur, S.; Akköse, M.
This study determines the dynamic characteristics of a prototype arch dam-reservoir-foundation system using Operational Modal Analysis method. Achievement of this purpose involved construction of a prototype arch dam-reservoir-foundation system under laboratory conditions. Ambient vibration tests on the arch dam model identified its natural frequencies, mode shapes, and damping ratios. Natural excitations such as small impact loads vibrated to arch dam. Sensitivity accelerometers which were placed on the dam's crest collected signals in measurements. Measurements were recorded for empty and full reservoirs. Operational Modal Analysis software processed signals which were collected from the ambient vibration tests. Enhanced Frequency Domain Decomposition technique estimated dynamic characteristics of the dam. Results showed that there was an approximate 20-25% difference between natural frequencies related to empty and full reservoirs.
- BildiriYalnız künye2011Ambient and forced vibration tests of a box girder concrete bridge model
Altunisik, A.C.; Bayraktar, A.; Sevim, B.
In this paper, ambient and forced vibration tests of a box girder laboratory con-crete bridge model are described to obtain experimental dynamic characteristics such as natural frequencies, mode shapes and damping ratios. The bridge deck consists of a main span of 3m and two side span of 1.5m each. The total bridge length is 6m and width of bridge is 0.60m. Heights of the bridge column and bridge deck are 0.80m and 0.30m, respectively. In the forced vibration tests, excitation of the bridge model is induced by an impact hammer. The ambient vibration tests are conducted under natural excitation such as wind and small impact effects. The Enhanced Frequency Domain Decomposition method in the frequency domain and the Sto-chastic Subspace Identification method in the time domain are used to extract the dynamic characteristics. At the end of the study, dynamic characteristics obtained from ambient and force vibration tests are compared with each other. It is seen that there is a good agreement be-tween both results and they are nearly closed to each other.
- BildiriYalnız künye2011Operational modal testing of an arch type steel highway bridge using SSI technique
Altunişik, A.C.; Bayraktar, A.; Sevim, B.
The paper determines the dynamic characteristics of an arch type steel highway bridge applying ambient vibration testing. A modern steel highway bridge which has arch type structural system with 216m total length and located in the Ayvacik county of Samsun, Turkey is selected as an application. Because of the fact that the bridge connects the villages which are separated with Suat Ugurlu Dam Lake, it has a major logistical importance for this region. The construction of the bridge completed in 2009 and opened the traffic. The experimental meas-urements are carried out by ambient vibration tests under traffic loads. Vibration data are gath-ered from the bridge deck. Measurement time, frequency span and effective mode number are determined considering similar studies in the literature and initial finite element analysis re-sults. Stochastic Subspace Identification technique (SSI) in the time domain are used for the output only modal identification and dynamic characteristics such as natural frequencies, mode shapes and damping ratios are determined, experimentally.