Seite - 1479 - in Book of Full Papers - Symposium Hydro Engineering

displacements and accelerations for the four earthquakes. It is clear that dam natural period has significant effect on dam seismic behavior. Natural period for KOYNA dam for first mode of vibration equals 0.38 sec. It is noticed that Aqaba-EW earthquake has the maximum and EL-Centro has the minimum spectral displacement and acceleration. Conclusions Based on the results presented in this study, the following conclusions can be drawn: 1. Foundation stiffness affects modal properties and an increase from EF/EC = 0.50 to 5 leads to significant decrease in natural period. For EL-Centro earthquake-S00E component, when EF/EC ratio changed from 0.50 to 5.0 a significant difference in displacement and acceleration occurred. This difference explain the effect of foundation stiffness on seismic behavior of the dam. 2. For static and seismic analysis, foundation stiffness has a pronounced effect on dam displacements and normal stresses up to EF/EC = 2.0. Up to this value foundation stiffness shouldn’t be ignored in dam simulation and analysis especially if foundation stiffness less than two times dam concrete stiffness. When EF/EC equals 5.00, it is recommend to assume fixed base to simplify the problem. 3. Ground motion variation affects dam seismic response, although the different ground motions have the same peak acceleration. This difference is dependent on the frequency content of earthquake and the dynamic characteristics of the dam. References 1. Akkose, M. and E. Simsek (2010) "Non-linear seismic response of concrete gravity dams to near-fault ground motions including dam-water-sediment-foundation interaction." Applied Mathematical Modeling 34(11): 3685-3700. 2. Arabshahi, H. and V. Lotfi (2008). "Earthquake response of concrete gravity dams including dam-foundation interface nonlinearities." Engineering Structures 30(11): 3065-3073. 3. Bhattacharjee, S. S. and P. Leger (1994). "Application of NLFM models to predict cracking in concrete gravity dams." Journal of Structural Engineering 120(4): 1255-1271. 4. Bhattacharjee, S. S. and P. Leger (1995). "Fracture response of gravity dams due to rise of reservoir elevation." Journal of Structural Engineering 121(9): 1298-1305. 5. Binnie, A. (1973). "The theory of flexible dams inflated by water pressure." Journal of Hydraulic Research 11(1): 61-68. 6. Bougacha, S., J. M. Roesset and L. Tassoulas (1993). "Dynamic stiffness of foundations on fluid- filled poroelastic stratum." Journal of engineering mechanics 119(8): 1649-1662. 7. Bougacha, S., J. L. Tassoulas and J. M. Roesset. (1993). "Analysis of foundations on fluid-filled poroelastic stratum." Journal of engineering mechanics 119(8): 1632-1648. 8. Chopra, A. K. (1967). "Hydrodynamic pressures on dams during earthquakes." Journal of the Engineering Mechanics Division 93(6): 205-224. 9. Chopra, A. K. and P. Chakrabarti (1981). "Earthquake analysis of concrete gravity dams including dam-water-foundation rock interaction" Earthquake engineering & structural dynamics 9(4): 363-383. 10. Dasgupta, G. and A. K. Chopra (1977). Dynamic stiffness matrices for homogeneous viscoelastic halfplanes. 11. Domanguez, J., R. Gallego and Bernardo. R (1997). "Effects of porous sediments on seismic response of concrete gravity dams." Journal of engineering mechanics 123(4): 302-311. 12. Fenves, G. and A. K. Chopra (1984). EAGD-84: A computer program for earthquake analysis of concrete gravity dams, Report No. UCB/EERC-84/11, Earthquake Engineering Research Center, University of California, Berkeley, 78 pp. 13. Fenves, G. and A. K. Chopra (1984). Earthquake analysis and response of concrete gravity dams, Report No. UCB/EERC-84/10 , Earthquake Engineering Research Center, University of California, Berkeley, 213 pp. 14. Ghanaat, Y. (2004). Failure modes approach to safety evaluation of dams. Proceedings of the 13th World Conference on earthquake engineering. 1479