Dynamic Behaviour of Arch Dams

Abstract

Probably the most important, and yet the most difficult aspect of designing arch dams for seismic forces is that of determining what such forces will be. As with all structures, determining seismic design parameters for a site requires the analysis of data from geologic, geophysical, seismological and geotechnical studies. For the site region, such studies are used to develop statistical and deterministic models to characterise the earthquake source, the wave propagation path and the local ground response. The required data is obtained from observational and instrumental data from earthquakes and aftershocks, regional seismicity networks, geologic mapping, geophysical and corresponding laboratory measurements and analytical models. Because of the uncertainties in such data, the design process normally adopts a conservative stance, examples of which include the following:

• 1 Using a rare event as the maximum possible earthquake because the location and magnitude of potential earthquakes are uncertain.

• 2 Using upper-bound values for the peak ground acceleration expected at the site because of uncertainties in attenuation laws.

• 3 Using upper bound values for the design response spectrum because of the variation in such calculated spectra for the same peak value of ground acceleration and/or intensity.