New building code requirements for the seismic design of tall buildings near active faults

Abstract

The seismic provisions in the new 1997 edition of the Uniform Building Code (UBC) contain significant changes affecting the seismic resistant design of buildings. For buildings in California, the most significant change is related to the amplification of forces in areas near major active faults. This is done through the introduction of a near-source factor. This factor affects the design of buildings throughout the spectral range, but particularly affects mid-rise and high-rise buildings owing to their response to long period ground motions for which the near source effect is most pronounced. This paper provides an overview of the code change, a detailed discussion of ground motion mapping in the near field, and a discussion of the effect of the code change on tall buildings. Preliminary near-source maps are developed for the Los Angeles Basin. Studies are presented, comparing base shear values calculated based on the 1994 and 1997 editions of the Uniform Building Code. © 1997 John Wiley & Sons, Ltd.