PB86-135027 REPORT NO. EARTHQUAKE ENGINEERING RESEARCH CENTER UCB/EERC-85/11 OCTOBER 1985 DYNAMIC INTERACTION EFFECTS IN ARCH DAMS by R. W. CLOUGh K.-T. CHANG H.-Q. CHEN Y. GHANAAT Report to the National Science Foundation on ResectrCh conducted underthe U.S.-China Protocol for Scientific and Technical Cooperation in Earthquake Studies COLLEGE OF ENGINEERING REPRllllUCEll BY . NATIONAL TECHNICAL UNIVERSITY OF CALIFORNIA • Berkeley, California INfORMATION SERVICE u.s.DEPARTMENTllF CllMMERCE SPRINGFIELD,VA. 22161 I ForsalebytheNationalTechnicallnforma tionService,U.S.DepartmentofCommerce, Springfield, Virginia 22161. See back of report for up to date listing of EERC reports. DISCLAIMER Anyopinions,findings, and conclusions or recommendationsexpressedinthispublica tion are those of the authors and do not necessariIyreflecttheviewsoftheNational Science Foundationorthe Earthquake En gineering Research Center, University of California, Berkeley DYNAMIC INTERACTION EFFECTS IN ARCH DAMS by R. W. Clough, K.-T. Chang H.-Q. Chen, Y. Ghanaat A Report on Research Conducted under the U.S.-China Protocol for Scientific and Technical Cooperation in Earthquake Studies Report No. UCB/EERC-85/ll Earthquake Engineering Research Center University of California Berkeley, California October 1985 i ABSTRACT This report summarizes the results obtained and the conclusions drawn from a four year cooperative research project on "Interaction Effects in the Seismic Response of Arch Dams". The work has been done under the U.S.-China Protocol for Scientific and Technical Cooperation in Earthquake Studies,by the Scientific Research Institute for Water Conservancy and Hydroelectric Power and Tsinghua University, both of Beijing, China, collaborating with the Earthquake Engineering Research Center of the University of California, Berkeley. The central feature of the research was correlation of field measurements of the forced vibration response of two arch dams in China, Xiang Hong Dian and Quan Shui, with corresponding results predicted by computer analyses; the principal emphasis of the work was on the effects induced by dynamic interaction of the foundation rock and the reservoir water with the response of the dams. The results demonstrated that the foundation rock does participate significantly with the forced vibrations of the dams, but that this type of interaction can be represented adequately by including a block of foundation rock with the dam in forming the finite element mathematical model. Using a block with dimensions equal to the height of the dam in directions upstream, downstream, and radially outward from the dam base is adequate if a rock modulus consistent with the static test data is applied. Similarly these results clearly show the inportant influence of the reservoir water interacting with the dam, and demonstrate that complicated reservoir geometries can be modelled effectively using liquid finite elements. However, the very important question of whether the reservoir water should be treated as compressible or incompressible in the mathematical model has not been answered by these analyses,which assumed ii incompressibility. Discrepancies between measured and calculated hyrdo dynamic pressures, especially for Quan Shui dam, suggest that the water should be treated as compressible, but further research is needed to explain the differences in the correlation obtained for the two dams and also to demonstrate the significance that co~ressibilityhas on response to earthquake motions (as compared with harmonic excitation). Preliminary studies performed during this project demonstrated that the interacting foundation rock also plays an important part in the earthquake response behavior of arch dams, and that further study is needed on seismic input aspects of the foundation interaction mechanism. Continuing research by the cooperating institutions is proposed to obtain final answers to the remaining questions about reservoir and foundation interaction. iii PUBLICATION NOTE This report is being published simultaneously by the Scientific Research Institute for Water Conservancy and Hydroelectric Power of Beijing and by the Earthquake Engineering Research Center of the University of California, Berkeley. The report produced by each organization is provided with the standard cover for that organization.