From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
Date: Thu, 22 Feb 2001 12:32:09 -0500
Scott Maxwell wrote:
. > Now about firewalls...
. > The first thing is to realize that there is a difference between a
. > firewall and a fire separation wall. A fire separation wall is a wall
. > between two spaces that is meant to stop or slow the spread of fire. A
. > fire wall is essentially a fire separation wall that MUST remain standings
. > AFTER one side of the building has collapsed (or is one of the two
. > buildings has collapsed).
. > If you must have a firewall, then that wall between the two buildings must
. > be designed in a fashion that it would remain standing if either building
. > collapses. Thus, if the new building falls, then the fire wall MUST
. > remain standing or if the existing building falls, then the fire wall MUST
. > remain standing.
. > This can typically be done one of several ways. You can:
. > 1) [snip]
. > 2) Do a single wall that is tied to each structure that has "break away"
. > connections so that one side can fall without causing the other to
. > collapse or bringing down the wall. With a masonry wall with wood joists,
. > this has traditionally been done with a "fire cut".
. > 3) [snip]
It seems to me that a "fire wall" would be virtually impossible in seismic
country as the code requires that the diaphragm be tied to masonry/concrete
walls. "Fire cuts" would be ineffective as the joists are tied to the wall
with "tension ties" or other anchors. A "fire cut" would only be effective
for wood joists resting on or in walls without any other type of connection
between the joist and the wall. For a fire cut to be effective with tension
ties, the tension tie would have to be a fusable link and even then it is
questionable whether that would work, e.g., a fire destroys the wood joist at
mid-span, but does not reach releasing temperature at the fusable link at the
A. Roger Turk, P.E.(Structural)