International Symposium Qualification of dynamic analyses of dams and their equipments and of probabilistic assessment seismic hazard in Europe th August 2nd September 2 Saint-Malo Session Investigation on the Dynamic Characteristics and Seismic Behaviors of Aratozawa Dam Z. Cao JP Business Service Corporation N. Matsumoto, N. Yasuda, M. Naruoka Japan Dam Engineering Center Saint-Malo Yannick LE GAL
SUMMARY With the earthquake records over a period of about 2 years, followings are analyzed. To investigate the dynamic characteristics and their variations Fundamental frequency Acceleration amplification ratio To investigate the propagation behavior of seismic motions in dam foundation system Cross spectrum Coherence function 2
. MAIN FEATURES OF ARATOZAWA DAM Dam type Dam height 7.m Crest length.7m Crest width.m Slope gradients Design seismic coefficient Rockfill dam with central clay core Upstream: :2.7 Downstream: :2.. (dam body),.8 (intake tower, bridge),. (spillway)
2. EARTHQUAKE MONITORING T, M, F (cm/s2) Crest (T) Max: Min:-2 - - 2 8 (sec) G 8m m m T M F m m 27.7m Locations of Seismographs (cm/s2) Middle of core (M) Max:2 Min:- - - 2 8 (sec) (cm/s2) Foundation (F) Max:2 Min:-7 - - 2 8 (sec) Earthquake Records in Stream Dir. Iwate-Miyagi Nairiku Earthquake, 28
Period Number of Records A max (cm/s 2 ) 992-2 > > > 7 > 2-2 - 2-2 - Stream Dir. 2 - -2 2-2 - 2-2 - Axial Dir. 2 - -2 2-2 - 2 2-2 - Vertical Dir. 2 (a) Crest(T) 2 - -2 2 - - - - Stream Dir. - - - - - - Axial Dir. - - - - 2 - - Vertical Dir. 2 - - 2 (b) Foundation(F) 997/2/7 2:: 999// :: 2/2/8 22:8:7
. THE WORK WE VE DONE Analyses Main objectives Records used Spectrum and transfer function Investigation on the amplification ratio Cross spectrum and coherence function To investigate the variation of the fundamental frequency of the dam To find the variation of amplification ratio of the dam body To investigate the propagation behavior of seismic motion in dam foundation system records 2 cm/s 2 < A max < 2 cm/s 2 8 records, A max cm/s 2, A max 7, A max, A max 2, A max > Same as above
. SPECTRUM & TRANSFER FUNCTION - Transfer Function Stream Dir. 2 Amplification 2 Cross stream Dir. Vertical Dir. 2 2 2 2 Frequency(Hz) 2// 2:7: 22// ::2 2// :: 7
-2 Fundamental Frequencies of the Dam.2 Stream Dir. 2.9 Stream Dir. Fundamental Frequency(Hz) 2 2 2 7 8 9 2 7 8 9 2 2 22 2 2 2 2 27 28 29 2 992 9 9 9 99 97 99 28 9 2 2. Cross stream Dir. 2.8 Cross Stream Dir. 2 7 8 9 2 7 8 9 2 2 22 2 2 2 2 27 28 29 2 992 9 9 9 99 97 99.8 28 9 2 2 Vertical Dir. Vertical Dir.. 2 7 8 9 2 7 8 9 2 2 22 2 2 2 2 27 28 29 2 992 9 9 9 99 97 99 28 9 2 2 8
. AMPLIFICATION RATIO ANALYSIS - Epicenters of the Selected Earthquakes km N km 2km 2 km km 29 8 km 2 7 8 7 Down stream 8 7 8 records before and after 28, A max cm/s 2, A max 7, A max, A max 2, A max > 9
-2 Features of the Selected Earthquakes No. Time of occurrence M Focal depth (km) A max of found. (cm/s 2 ) 99/8/ :2. 9 28 2 99/8/ 8:.8 99/8/ :.9 2//2 8:2 7. 72 28// 8: 7.2 8 2 28// 9:.2 99 7 28// 9:. 7 82 8 28// 9:. 9 28// 9:2.7 7 7 28// :.8 7 2 28// 2:9. 8 92 2 28// 2:.8 9 79 28// 9:. 8 229 28// 2:. 7 7 28/7/2 :2.8 8 27 28/9/2 :. 9 7 2// : 9. 2 2 8 2//7 2:2 7.2 2
- Investigation Method Peak acc. of crest Amplification ratio= Peak acc. of foundation Fundamental freq. Transfer function of dam body Dominant freq. 2 Fourier spectrum of ground motion
- Amplification Ratio(/) Amplification Freq.(Hz) Acc.(cm/s 2 ) 2 8 2 Stream Direction 2 7 8 9 2 7 8 99 2 Max. acc. of the foundation Dominant freq. of the earthquake ー Fundamental freq. of the dam Acceleration amplification ratio 2 7 8 9 2 7 8 2 7 8 9 2 7 8 28 2 8/ :2 8/ 8: 8/ : /2 / 8:2 8: / 9: / 9: / 9: / 9:2 / : / 2:9 / 2: / 9: / 2: 7/2 :2 9/2 : / /7 :2:2 2
- Amplification Ratio(2/) Acc.(m/s 2 ) 2 Cross Stream Direction Max. acc. of the foundation Dominant freq. of the earthquake ー Fundamental freq. of the dam Amplification ratio of the dam 2 7 8 9 2 7 8 Freq.(Hz) Amplification 8 2 2 7 8 9 2 7 8 2 7 8 9 2 7 8 8/ :2 99 8/ 8: 8/ : 2 /2 8:2 / 8: / 9: / 9: / 9: / 9:2 / : 28 / 2:9 / 2: / 9: / 2: 7/2 :2 9/2 : 2 / /7 : 2:2
- Amplification Ratio(/) Acc.(m/s 2 ) 2 Vertical Direction Max. acc. of the foundation Dominant freq. of the earthquake ー Fundamental freq. of the dam Amplification ratio of the dam 2 7 8 9 2 7 8 Freq.(Hz) Amplification 8 2 2 7 8 9 2 7 8 99 2 2 7 8 9 2 7 8 28 2 8/ :2 8/ 8: 8/ : /2 8:2 / 8: / 9: / 9: / 9: / 9:2 / : / 2:9 / 2: / 9: / 2: 7/2 :2 9/2 : / /7 : 2:2
- Amplification Ratio(/) Amplification ratio 2 Stream direction Amplification ratio 2 Cross stream direction The max. acc. of foundation(cm/s 2 ) The max. acc. of foundation(cm/s 2 ) Vertical direction Amplification ratio 2 Other earthquakes 28 Earthquake and its aftershocks Approximate line The max. acc. of foundation(cm/s 2 )
. PROPAGATION BEHAVIOR OF SEISMIC MOTION - Analytic Methods assuming two propagation paths F T and G T ) cross spectrum 2) coherence function ) transfer function T G F Right abutment
Definition: T F Transfer Function D = S TF T S F Cross Spectrum W = S TF T S F Coherence Function C = W W TF TF 2 ( ) TT W FF 7
Earthquakes to be analyzed Original status 2min after the strong earthquake years after Freq.(Hz) Amplification 2 8 2 2 7 8 9 2 7 8 2 7 8 9 2 7 8 99 2 28 2 8/ :2 8/ 8: 8/ : /2 / 8:2 8: / 9: / 9: / 9: / 9:2 / : / 2:9 / 2: / 9: / 2: 7/2 :2 9/2 : / /7 :2:2 8
Amplification Spectrum(cm 2 /s 2 ) 2 2 2. (Hz) 2.9 (Hz) Transfer function Cross spectrum Coherence G-T F-T Original status in 99.8...2 2 7 8 9 Frequency(Hz) Stream direction (Aug.,:2, 99) 9
Amplification Spectrum(cm 2 /s 2 ) 2 2. (Hz) Transfer function Cross spectrum Coherence G-T F-T Original status in 99.8...2 2 7 8 9 Frequency(Hz) Cross stream direction (Aug.,:2, 99) 2
Amplification 2 Transfer function G-T F-T Spectrum(cm 2 /s 2 ) 2 Cross spectrum Coherence Original status in 99.8...2 2 7 8 9 Frequency(Hz) Vertical direction (Aug.,:2, 99) 2
Amplification 2 2. (Hz) Transfer function Cross spectrum G-T F-T Spectrum(cm 2 /s 2 ) 2 Coherence Just after the strong earthquake.8...2 2 7 8 9 Frequency(Hz) Stream direction (June,9:, 28) 22
Amplification Spectrum(cm 2 /s 2 ) 2 2 2. (Hz) Transfer function Cross spectrum Coherence G-T F-T Just after the strong earthquake.8...2 2 7 8 9 Frequency(Hz) Cross stream direction (June,9:, 28) 2
Amplification 2 Transfer function G-T F-T Spectrum(cm 2 /s 2 ) 2 Cross spectrum Coherence Just after the strong earthquake.8...2 2 7 8 9 Frequency(Hz) Vertical direction (June,9:, 28) 2
Spectrum(cm 2 /s 2 ) Amplification 2 2.88 (Hz) 2. (Hz) Transfer function Cross spectrum Coherence G-T F-T About years later.8...2 2 7 8 9 Frequency(Hz) Stream direction (April 7,2:2, 2) 2
Spectrum(cm 2 /s 2 ) Amplification 2 2 2.2 (Hz) Transfer function Cross spectrum Coherence G-T F-T About years later.8...2 2 7 8 9 Frequency(Hz) Cross stream direction (April 7,2:2, 2) 2
Amplification 2 Transfer function G-T F-T Spectrum(cm 2 /s 2 ) 2 Cross spectrum Coherence About years later.8...2 2 7 8 9 Frequency(Hz) Vertical direction (April 7,2:2, 2) 27
CONCLUDING REMARKS The Earthquake in 28 caused a sharp drop of the fundamental frequencies, which later recovered, but accompanied with anisotropy. The amplification ratio show the same variation tendency as that of the fundamental frequency. In the low frequency domain up to the fundamental frequency, the effect of the seismic motions of the lower bedrock is greater than that of the abutment. While, it shows opposite tendency in the higher frequency domain. 28
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