NEW BUILDING CODE REQUIREMENTS FOR THE SEISMIC DESIGN OF TALL BUILDINGS NEAR ACTIVE FAULTS

The seismic provisions in the new 1997 edition of the Uniform. Buildin g Code (UBC) contain significant changes affecting the seismic resista nt design of buildings. For buildings in California, the most signific ant change is related to the amplification of forces in areas near maj or active faults. This is done through the introduction of a near-sour ce factor. This factor affects the design of buildings throughout the spectral range, but particularly affects mid-rise and high-rise buildi ngs owing to their response to long period ground motions for which th e near source effect is most pronounced. This paper provides an overvi ew 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 o n tall buildings. Preliminary near-source maps are developed for the L os Angeles Basin. Studies are presented, comparing base shear values c alculated based on the 1994 and 1997 editions of the Uniform Building Code. (C) 1997 John Wiley & Sons, Ltd.