Earthquake Loading

Even in the most seismic areas of the world the occurrence of destructive earthquakes is a rare event. Earthquake loads differ from ordinary design loads in various aspects. Not only the occurrence, but also the loading itself is highly uncertain with respect to magnitude, frequency content and duration of the ground shaking. Naturally, it is not economical to design structures which resists the “strongest possible” earthquake, since it is very unlikely that a structure ever experiences such a strong shaking. It is generally accepted in design, that a structure should resist moderate earthquakes without damage, but to permit yielding and damage for very rare strong earthquake events provided the structure is unlikely to endanger human life by collapse. The required resistance to possible future earthquake loading depends, of course, on the consequences of structural failure. In case of dams, power plants and important life lines, the design will be more conservative.