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Re: Firewalls

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To engineers interested in fire walls,

	Thank you, Michael, for revisiting this subject.  I think more
discussion on this subject is warranted.

	I read the previous discussion with interest since I happened to have a
4 hour wall to design at the time.  Unfortunately (for me) the
discussion ended before I had all of my thoughts organized.  I have
since concluded that some parts of the topic have not yet been
discussed.  I would be interested in participating in further
discussions on this topic if there are any others interested.

	For openers, what about lateral loading on the wall after the fire is
over?  How long must the wall last after the fire?  What about the
stability of the remaining building?

	I discussed these concerns with architect clients and engineering
colleagues who essentially said "It's not a problem; don't worry about
it; the fire fighters will pull the wall down after the fire anyway." 
The fire marshal's office would neither deny or confirm this.  The plan
checker's office said that I was the EOR so it was my responsibility. 
But there are very few guidelines in the code to define what I am
responsible for.  Big help!

	I finally decided, arbitrarily, to design my wall as a free-standing
wall subjected to a 3 p.s.f. (5 p.s.f. ultimate) wind load.  This is
about half of the suction side wind load in open exposure and close to
the wind load for the sheltered environment of city suburbs.  Seismic
loading isn't a major concern in Calgary; a few years ago we changed
from zone 0 to zone 1; we're unlikely to have an earthquake immediately
after a fire.

	In California, on the other hand, it's possible that an earthquake
might cause the fire; and you might want to think about aftershocks. 
I'm interested in what other concerns you might have.  I'm also
interested in your solutions.

	There are also load bearing considerations to take into account. 
Friction from contact with loaded (or unloaded) floors could help
stabilize otherwise unsupported walls.  What kind of loading might this
friction add?  Transfer of shear loading to a wall should be easy with
some sort of key way.

	Anyway, I hope I'm not rambling on too much.


				H. Daryl Richardson,

Michael Zaitz wrote:
> Hello All;
> Sometime back the issue of 4 hour firewalls that allows the structure to
> collapse on either side of the wall without affecting the structure on
> the other side of the wall.   I have a wall that is now required to be a
> 4 hour wall (due next week) and as such I need to do something to allow
> the collapse.  To make matters worse the wall is a shear wall (or at the
> moment it is).  I remember talk of anchors that will melt of allowing
> the structure to fall but did not see anything in the archives that had
> any manufacturers or the like.  Coould someone provide me with some
> information or some leads as to where to find information on these types
> of anchors?
> Thanks,
> Mike