Current Situation of JCOLD Activity about Seismic Data - Relevance of New Bulletin Seismic Interpretation of Integrated Observation Data -

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1 June 3, 2014 ICOLD 2014 Annual Meeting in Bali Committee of Seismic Aspects of Dam Design Current Situation of JCOLD Activity about Seismic Data - Relevance of New Bulletin Seismic Interpretation of Integrated Observation Data - Takashi SASAKI JCOLD (Japan Commission on Large Dams) 1. Past situation about preparation of New Bulletin - Preliminary draft in 2008 by Dr. Matsumoto, the former committee member from Japan [See RM-1] Contents 1. NATURAL PERIOD OF DAMS COMPUTED FROM RECORDED STRONG MOTIONS 2. AMPLIFICATION RATIO OF PEAK ACCELERATION AT DAMS OBTAINED FROM RECORDED STRONG MOTIONS 3. RELATION AMONG MAGNITUDE OF EARTHQUAKES, EPICENTRAL DISTANCE AND PERFORMANCE OF DAMS 4. COMPARISON OF PGA AT DAM FOUNDATIONS, SOILS AND UNDERGROUND Chapter 1 was written using seismic data in Acceleration Records on Dams and Foundation No.2 published in 2002 by JCOLD. Chapter 2 was written using data from Japan, USA and other countries. Chapter 3 was written using ICOLD Bulletin 120 (2001), Japan (Reports of Public Works Research Institute) and USA (USCOLD Observed Performance of Dams during Earthquakes Vol.Ⅱ (2000). Chapter 4 was written using data sets from several technical papers about the 10 major earthquakes occurred from 1978 to 2004 in Japan - Progress of analysis of seismic data shown in the report published in ICOLD Europe Club, 2010 [See RM-2] This report was written based on analysis results of seismic data including recent major earthquake in Japan. But, such data did not include data obtained during the Tohoku Earthquake in

2 The contents of this report will be helpful to revise the Chapters 1,2 and 4 in the preliminary draft of new bulletin. Tohoku Earthquake was occurred in March 2011 in Japan, and a lot of seismic data were observed and recorded at many dams. So, this committee decided to include the knowledge which would be got from valuable data obtained during Tohoku Eq. in this new bulletin. 2. JCOLD Activity on Compilation of Acceleration Data obtained in Dams JCOLD had collected strong motion records observed during past earthquakes in Japan, and published two technical materials. Technical material No.1 was made in 1978, and No.2 in No.1 dealt with 14 earthquakes during 1966 to 1974 and 10 dams. No.2 dealt with many earthquakes during Jan to Oct including the 1995 Kobe Earthquake and the 2000 Tottori-Seibu Earthquake and 84 dams. * Japanese National Committee on Large Dams Earthquake Records on Rock Foundation No.1, * Japan Commission on Large Dams Acceleration Records on Dams and Foundation No.2, Last year, JCOLD organized the committee on Revision of Database of Dam Seismic Data to compile strong motion records during recent earthquakes after the Tottori-Seibu Earthquake in 2000 with considerable cooperation from dam owners in Japan. Of course, those records are included the strong motion data observed during the 2011 Tohoku Earthquake and the aftershocks. The committee in JCOLD have been making efforts to make a technical material about strong motion records titled Acceleration Records on Dams and Foundation No.3. [See RM-3] This technical material will include newly collected data (from 2000 to 2011, number of earthquake: 201) with data (from 1978 to 2000) already compiled in the Acceleration Records on Dams and Foundation No.2. The conditions of the distribution of No.3 will be decided based on the agreement of dam owners who provided the strong motion data. Outline of Seismic Data which will be included in Acceleration Records on Dams and Foundation No.3 Number of Dams Number of EQs Number of Data Sets (Number of Dams by Number of EQs) * About 9 % of total data sets is from Tohoku Earthquake. 2

3 3. Current situation of the JCOLD activity Collecting work of data from dam owners has finished. But, checking of data have not finished, and such work is very time-consuming. We, JCOLD would like to publish the technical material Acceleration Records on Dams and Foundation No.3 by the end of 2014 Japanese fiscal year (that is, March 2015) at the latest. Besides the making work of that technical material, JCOLD have started and been conducting several analyses of acceleration data, for examples, amplification ratio of dam crest to bottom, fundamental natural frequency of dams. And, JCOLD will make a technical report about the analyses results of acceleration data with the case studies on numerical reproduction analyses of dynamic behaviors about several dams. Those analyses results will be used to add valuable information including the Tohoku Earthquake in the new bulletin Seismic Interpretation of Integrated Observation Data The followings are examples of analyses results made using collected data up to now. Those are tentative version. 3

4 Amplification of Concrete Gravity Dams Amplification of Rockfill Dams 4

5 1 st Resonant Period of Concrete Gravity Dams 1st Resonant Period of Rockfill Dams 5

6 4. Point of View in Consideration for Analyses Results of Acceleration Data The followings would have effects on the amplification ratio of dam body and the resonant period of dam body. - Water Level during Earthquake (especially for Concrete Dams) - Non-linearity of Dam Material (especially for Rockfill Dam and Earthfill Dam) - Seasonal Change of Temperature (especially for Concrete Dams) - Dam Configuration Characteristics - Ratio : Crest Length / Dam Height < Non-linearity of Dam Material > Frequency response of rockfill dam are changed due to the earthquake level (max. acc.). Fourier Amplitude Ratio (Transmission Function) of Dam Crest to Bottom Aratozawa Dam Main Shock: 2008 Iwate-Miyagi Inland Earthquake, Max. acc. at bottom: about 1G 1996 (Nos.1-3): Max acc. at bottom: about 0.3G (Ref.: Ohmachi and Tahara Nonlinear Earthquake Response Characteristics of A Central Cray Core Rockfill Dam, Soils and Foundations, Vol.51, No.2, Japanese Geotechnical Society, Arp. 2011) 6

7 1st Resonant Period (sec) Aratozawa Dam Max. Acceleration at Bottom (Gal) (This figure is made by Public Works Research Institute in Japan) < Temperature Effects> Frequency response (natural frequency) of concrete gravity dam would be changed due to temperature of the air. The one of possible cause of that phenomena is the constraint condition between transversal joints. Height of 65 m, Seismic motion record: 113, Microtremors record; 4 (Ref: Kahima, Kondo, Enomura and Sasaki Effects of Reservoir Water Level and Temperature on Vibration Characteristics of Concrete Gravity Dam, Symposium at ICOLD 2014 Bali) 7