A PROTOTYPE 2007 SEISMIC DESIGN CATEGORY MAP FOR RESIDENTIAL CONSTRUCTION IN THE STATE OF WASHINGTON

The new International Residential Code 2006 (2006 IRC) recently published by International Code Council (ICC) requires changes in seismic design category (SDC) determination given in IRC 2003. In the new determination the design category D₁ (0.50g < SDS ≤ 0.83g) is subdivided into categories D₀ (0.50 < SDS ≤ 0.67) and D₁ (0.67 < SDS ≤ 0.83). It is anticipated that the category change in D₁ will be more pronounced in western Washington where population and housing developments are larger.

In response to the new IRC 2006, our plans are also to update and make changes on 2007 Seismic Design Category Maps for Residential Construction (2007 SDCMRC) in Washington State. New prototype 2007 SDCMRC for Washington State will be generated using the same methodology as Poelstra and Palmer (2004). The new 2007 seismic design map will be official in July 2007.

Reference: Poelstra, James L.; Palmer, Stephen P., 2004, Seismic design category maps for residential construction in Washington: [accessed Feb. 6, 2007 at http://www.dnr.wa.gov/geology/hazards/hmgp.htm]