Firewall Design
Firewall Design
(OP)
What kind of lateral loads (wind, seismic) does a rated wall (now cantilever)see after the structure around it has burned down? What if the wall is 25' tall?
TIA
TIA
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RE: Firewall Design
RE: Firewall Design
What is the code intention of this wall:Separation(insulation) or structural integrity.
If it is the latter then wind may be important, but the former has already failed to serve its purpose if there is no structure on either side.
RE: Firewall Design
It may or may not be a structural wall. I always have assumed that the surroudning structure would keep it in place.
Remember that in most places - the fire department will be there in 15 minutes or less - usually.
RE: Firewall Design
RE: Firewall Design
The IBC code does not spell out that an interior fire wall has to be designed for full wind. It, however, does need to be designed for seismic whether it is interior or exterior.
Nor does FM, NFPA, NCMA, but the Canadian code suggests 10 psf but I believe that is an ultimate load. Some US engineers use only 5 psf (interior pressure)or seismic load whichever is higher.
I believe that it should be higher than 5 psf to accomodate thermal shock (heated wall hit with cold water from a fire hose)and incidental forces from those caused by flashing pulling away, etc. Perhaps the Canadian code has it about right but I do not know what research that was based upon.
RE: Firewall Design
1607.13 Interior walls and partitions.
Interior walls and partitions that exceed 6 feet (1829 mm) in height, including their finish materials, shall have adequate strength to resist the loads to which they are subjected but not less than a horizontal load of 5 psf (0.240 kN/m2).
RE: Firewall Design
RE: Firewall Design
Don Phillips
http://worthingtonengineering.com
RE: Firewall Design
When a structure collapses, the remaining firewall must resist forces produced by:
Thermal shock
flashing pulling away
pressures created by the collapsing structure
It would be great if there was some research on the magnitude of forces that these actions produce.
RE: Firewall Design
The NFPA Handbook says, "Fire separation between buildings can also be provided by two blank exterior walls of adequate fire resistance and located very close together. Each wall is tied to the frame in its building; collapse of the frame pulls the wall in, leaving the other wall to resist the fire." I've been involved with this solution on most multi-story projects. The catch is if there is access throughthe fire wall, a rated door is needed in each wall, which can lead to architectural function and detailing challenges.
To an extent, I agree with DonPhillips' assessment with respect to tieing the wall to the structure on each side with the caveat that we must be able to assure the collapsing bulding will not pull the wall down with it. Factory Mutual's "Property Loss Prevention data Sheet 1-22 says that if the wall is tied to the frame on either side, the "pull of the collapsing frame on the fire side of the wall can be resisted by the strength of the frame on the non-fire side". They go on to present an equation for calculating the "Horizontal Pull", but I've never felt comfortable enough with this approach to use it.
RE: Firewall Design
There has been much research on these forces for tilt-up wall panels - particularly in Australia.
Do a google on these and you should be able to find the design philosophy. Otherwise look at a book like this one (I havent verified the content):
http:
RE: Firewall Design
RE: Firewall Design