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A comparative study on the actual and estimated seismic response of Kiralkizi Dam in Turkey

2005-07-01
Çetin, Kemal Önder
Isik, NS
Batmaz, S
Karabiber, S
Kiralkizi Dam, a 120 in high earthfill dam located in Diyarbakir city, Turkey, was shaken by a moment magnitude, M-w = 4.6 earthquake at an epicentral distance of 8 km, on December 24, 2000, at 13:31 local time. The seismic response of the dam was assessed by using spectral ratios between (i) available crest and foundation records (C/F), (ii) horizontal and vertical components of the recorded motions (H/V), (iii) by performing 2 dimensional finite difference-based seismic response analyses (Flac-2D), and (iv) 1D elastic shear beam solutions. First mode of vibration of the dam in the transverse direction by all four methods were estimated in the range of 0.55 to 0.62 second. Similar close agreement was not observed in higher modal periods estimated by H/V technique as compared to the predictions by C/F, Flac-2D, shear beam analysis techniques. Thus, H/V technique was concluded to be useful for the estimation of the fundamental resonance frequency of a soil structure, but not for its higher harmonics as consistent with available limited literature. In the longitudinal direction, natural period of the dam was estimated as 0.28 and 0.82 second by H/V and C/F techniques, respectively. Such disagreement was explained by (i) differences in the definitions of the estimated periods, (ii) internal impedance contrast of the dam, (iii) contributions of 3D valley effects. Single seismometer record obtained from crest level was found to be inadequate for reliably assessing the response of a dam in the longitudinal direction, and it is recommended to install multiple seismometers both within dambody and the abutments. Last but not least, the results of these analyses were further compared by available accelograms recorded at three earthfill and rockfill dams from Japan. In general, it was concluded that the seismic response of Kiralkizi Dam is comparable and within the prediction ranges of available analyses methods and is consistent with the expected response of a dam this height.