From: "Sprague, Harold O." <SpragueHO(--nospam--at)bv.com>
Date: Fri, 5 May 2000 08:20:38 -0500
Look at page 37 of the NEHRP Commentary. The third paragraph of Section
4.1.1 discusses the lower bound margin of collapse of 1.5. The 2/3 factor
is the inverse of 1.5.
> -----Original Message-----
> From: Paul Crocker [SMTP:paulc(--nospam--at)ckcps.com]
> Sent: Thursday, May 04, 2000 12:32 PM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: NEHRP earthquake loading
> In the '97 NEHRP, seismic design is based on 2/3 of the 2,500 return
> earthquake (2,500 year return period = 2% probability of exceedance in 50
> years). Does anyone know what rationale is used to justify the 2/3? I
> read through the commentary, and can't seem to find anything about the
> I assume either it was an arbitrary decision about the design level to
> toward, or there is something specific about it that I am missing.
> Paul Crocker