Seismic design criteria
Martin Wieland
Abstract
Abstract Chapter 5 notes that the earthquake load case was considered for the first time in the 1930s, for concrete and embankment dams. At that time the ground shaking, which was the basic earthquake hazard considered, was represented by a seismic coefficient. For the seismic design of most dams, a horizontal seismic coefficient of 0.1 was used almost universally, irrespective of the seismicity of the dam site, which was usually not known. The pseudo-static approach has since been shown to be unreliable, and often unsafe, and is no longer used. This first became apparent at the Koyna dam in 1967, and with the large crest settlement that occurred at the Lower San Fernando dam in 1971. Chapter 5 also gives advice on the classification of dams, and points out that, as well as damage due to seismic shaking, other threats include fault movement beneath the dam (see Chapter 15) and earthquake-triggered landslides (see Chapter 17).