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- 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.