Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Fwd: Building drift and separation

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Please note that the 1994 UBC says (I'm paraphrasing)  to use 3Rw/8 
=  0.38Rw, to caclulate the drift of each adjacent structure, but 
that the 1997 UBC will increase this requirement to  0.7R.  
Thus, the drift caclulation and building separation requirements will 
double in the 1997 UBC.

The use of R vs Rw will have no effect, since the lateral forces
used to caclulate the deflections were originally divided by R or

Also, there are some proponents who believe that the actual
expected drifts can be even higher, especially for short period
structures (less than about 0.5 sec), and that the 0.7R is really
only suitable for structures with longer periods.  Countering 
these arguements is the fact thatthe UBC requires the building 
separation to be calculated as the sum of the displacements of both 
adjacent structures, which is an absolute worst case assumption.  
Probabalistically, the square-root-sum-of-squares is a more likely 
maximum (which I do not recommend using, for reasons given above). 
Martin Johnson
EQE International, Inc.

--- Internet Message Header Follows ---
Received: from ( [])
	by (8.8.5/8.8.5) with SMTP id TAA10112
	for <rlewis(--nospam--at)>; Fri, 18 Apr 1997 19:58:13 -0500 (CDT)
Received: from by (NTList 3.02.13) id fa018829;
Fri, 18 Apr 1997 17:53:02 -0700
Received: from EQE_IRV_01.EQE.COM by via ESMTP
	for <seaoc(--nospam--at)> id RAA21046; Fri, 18 Apr 1997 17:50:14 -0700
Received: from EQE_IRV_01/SpoolDir by EQE_IRV_01.EQE.COM (Mercury 1.31);
    18 Apr 97 17:54:29 +1100
Received: from SpoolDir by EQE_IRV_01 (Mercury 1.31); 18 Apr 97 17:54:15
From: "Martin Johnson" <mwj(--nospam--at)EQE.COM>
To: seaoc(--nospam--at)
Date: Fri, 18 Apr 1997 17:54:13 PST
Subject: Building drift and separation
Priority: normal
X-mailer: Pegasus Mail for Windows (v2.52)
Message-ID: <106B5A9198B@EQE_IRV_01.EQE.COM>
Reply-To: seaoc(--nospam--at)
Error-To: seaoc-ad(--nospam--at)
X-Loop: seaoc(--nospam--at)
X-Info: [SEAOC]
Owner: seaoc-ad(--nospam--at)
X-POP3-Rcpt: seaoc-ad(--nospam--at)
X-Sender: seaoc-ad(--nospam--at)
Precedence: list
X-ListMember: rlewis(--nospam--at) [seaoc(--nospam--at)]


Richard Lewis, P.E.
Missionary TECH Team

The service mission like-minded Christian organizations
may turn to for technical assistance and know-how.