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RE: Seismic Joints

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Gerard,

 

Don’t know if this helps any, but the SRSS method was reintroduced into the 2009 IBC. New section 1613.6.7. I believe the SRSS method will also be in ASCE 7-10.

 

Gary

Gary J. Ehrlich, PE
Program Manager, Structural Codes & Standards
National Association of Home Builders (NAHB)
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From: Gerard Madden, SE [mailto:gmse4603(--nospam--at)gmail.com]
Sent: Thursday, September 10, 2009 1:09 PM
To: seaint(--nospam--at)seaint.org
Subject: Seismic Joints

 

The ASCE 7 makes a very vague statement about building separations in section 12.12.3

In the good old UBC, we were using SRSS to determine the gap to avoid pounding.

The IBC 2006 Design guide volume I indicates that this gap should be the SUM of the inelastic deflections.

So, say for a building with a drift limit of 1% (an essential facility) with 50 feet to the roof, the gap would need to be 8.5" under the SRSS method. Under the IBC example it would need to be 12"

If I had a regular occupancy building and could use 2.5% drift, then I would need a 30" joint

50 feet is about a 4 story building....are we really going into 24 " seismic gaps for 8-9 story buildings now?

Feedback appreciated.

-gm