ASCE 7-05 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 is misinterpreted 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.
A very informative technical guidline for Seismic Design of Cast-in-Place Concrete Diaphragms Chords, and Collectors was recently published by NEHRP. it can be downloaded from the following link
A very informative paper about shear reversal or Back stay effects in Tall buildings.
Shear Reversals in Walls
A very interesting article was published in STRUCTURE magazine in November 2003 issue.
Click the following link to read the article.
An Introduction to Hi rise Design