Where is the Base?

ASCE 7 defined the base for seismic design as:

The level at which the horizontal seismic ground motions are considered to be imparted to the structure.

Most of the times this isĀ misinterpretedĀ or misunderstood that where the base is considered when determining the height of building for seismic calculations specially when the site is sloped or if the basement is open from one side.

Read the following article published in December 2009 issue of Structure magazine, this article will answer lots of questions.