I have had the same thoughts with a few buildings recently. It is easy to imagine a fire in a large building that doesn't melt enough of the connectors before a general collapse.
Even if you design a good structural connection that does break away, the architectural connection of the roofing to the masonry wall may not break away. That is the case with all the Canadian buildings of a wide-spread North American chain store at the moment. They are correcting the situation. I don't know if the US stores have been looked at for the same problem.
I think the only fool-proof method is to use a double masonry wall, i.e., 2 walls, each attached to the structure on its side only. Then, of course, you have to separate them enough for seismic movement. I will ask the engineer for the above situation to see if he has another solution.
Kevin
On Fri, Jan 23, 2009 at 8:57 PM, Rich Lewis <seaint04@lewisengineering.com> wrote:
Stuart,
Thank you for this information. I've thought about a melt-away type bolt,
but I wasn't sure this was an acceptable solution. What if the fire is
sufficiently far enough away not to cause the melt temperature, yet a
collapse pulls on the steel due to a collapse in the next bay or so? Is the
thinking that the fire was hot enough to cause a collapse nearby, it must be
hot enough at the bolts in order to melt it? Is this a common rational?
Has anyone published a paper on this that addresses wall bracing concepts?
Thanks again for your help.
Rich
From: Stuart, Matthew [mailto:mStuart@cmxengineering.com]
Sent: Friday, January 23, 2009 11:36 AM
To: seaint@seaint.org
Subject: RE: Fire Wall Connection
Connect the wall to each structure using Nylatron bolts. A ceramic/plastic
composite material that "melts" at 500 degrees, or almost 1/2 the
temperature that steel starts to deform. The material has high shear
capacity and is ideal for collector force connection to the wall.
_____
From: seaint04@lewisengineering.com [mailto:seaint04@lewisengineering.com]
Sent: Fri 1/23/2009 11:52 AM
To: Seaint
Subject: Fire Wall Connection
I know this has been addressed in previous messages. Unfortunately I'm
having trouble searching the SEAInt archives. Every time I put in a
search, no matter which radio button I push, it does a general web search
and not an exclusive archive search.
I have a 2 story steel framed building with a masonry fire separation wall.
IBC 702 definitions requires the wall to stand if the structure on either
side of the wall collapses. Ideally I would like to use the fire wall as a
shear wall for one side of the wall. I realize this may not be practical.
I'm wondering if someone has developed a detail for attaching to the wall
as a shear wall but breaking away when needed for a fire event.
I have seen someone else use a detail where they bolted an angle to the
face of the wall and welded a smooth stud to the bottom of the outstanding
leg. They then welded a horizontal plate from the steel beam that had a
hole in it for the stud to slide up and down. If the beam went down far
enough the stud pulled out of the hole. The idea is interesting, but I
think it has a flaw. If the beam is pulled horizontal, say towards the
center of collapse, it still pulls horizontally on the wall. I thought
maybe using a slot perpendicular to the wall instead of a hole, to let the
beam pull away, yet have resistance for a shear wall force, but I guess I
can't guarantee the beam would only be pulled in that direction due to a
collapse.
Can anyone describe to me a better detail?
Thanks for your help.
Rich
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