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RE: Expansion and seismic joints @ fire wall is high seismic zone

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Title: RE: Expansion and seismic joints @ fire wall is high seismic zone


The code requires buildings to be separated by a SRSS combination of their design story drifts regardless of the building periods.  There is an IBC requirement that firewalls remain standing after one side collapses. I have seen locations where the architect wants to put the seismic joint / thermal joint at the fire wall and does not want to have a double wall - two separate walls attached to each side of the joint.

NFPA 221 says you can have a double fire wall, tied fire wall or a cantilevered fire wall.  Tying fire walls across the seismic joint or expansion joint defeats the purpose of the joint. A cantilevered wall can possibly work for the NFPA 221 5 psf but it does not work well for seismic component forces when cantilevered, and butting the roof to wall on each side of the joint defeats the purpose.  The only way I can see making the situation work, in seismic design category D, is with a double fire wall - having a wall on each side of the joint tied to that portion of roof separated by the seismic joint.  Has anyone found a different solution to the problem?

Scott Haan.

-----Original Message-----
From: Will H [mailto:haynewp(--nospam--at)]
Sent: Friday, November 22, 2002 2:56 PM
To: seaint(--nospam--at)
Subject: Expansion and seismic joints

Should you allow enough of a gap in a roof thermal expansion joints (example
in single story metal deck) to satisfy the seismic joint  requirement as
well. I don't usually see this done. Since the buildings are acting
separately perpendicular to the joint, I think a seismic joint would be
  Also, is a seismic joint required when 2 buildings that have the same
period are next to each other. For example, I am separating 2 buildings by a
firewall. Each building butting up against the wall and not connected. If
each building is moving at the same period, can they still theoretically
smash together in an earthquake?

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