I am working on a 3-story building with a 2 hour firewall that cuts right through it. The building has concrete over metal deck floors and steel beams and columns. The building is located in a high seismic region and the floor diaphragm needs to be continuous through the wall. My thought was to select a floor thickness with a 2 hour rating so that the 2 hour wall is interrupted by another 2 hour element. The wall would be attached to the deck above and below on both sides with break away clips to satisfy the structural integrity requirements of the IBC. Does that seem like a solution that would satisfy the code requirements and keep the diaphragm intact? Has anyone come up with a different solution? I would love to see a detail if you have one!
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Firewall in multi-story steel construction
- Thread starter Zman42
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Here is a link to a SEAOSC opinion paper on the issue. It is not for the building type I am working on, but the concept is the same. It doesn't make sense to me to "create an unnecessary weakness in the structure" as the SEAOSC paper puts it, by breaking up the diaphragm.
I see what that article is saying. I guess all of my firewalls have been either block wall or poured concrete and therefore are as stiff or stiffer than the diaphragm.
In my location they generally don't build firewalls out of double stud walls. At least not that I've seen yet.
In my location they generally don't build firewalls out of double stud walls. At least not that I've seen yet.
The article is talking about wood frame construction. You are talking about a steel structure but you don't mention the type of firewall. Is it masonry?
If masonry, steel columns in a fire situation will expand much more rapidly than masonry and will tend to crack the firewall to such an extent that it no longer acts as a firewall.
Your detail needs to take into account the continuity of the deck and the continuity of the firewall, not a simple requirement.
BA
If masonry, steel columns in a fire situation will expand much more rapidly than masonry and will tend to crack the firewall to such an extent that it no longer acts as a firewall.
Your detail needs to take into account the continuity of the deck and the continuity of the firewall, not a simple requirement.
BA
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- #6
The article is about wood construction, but I think the concept is applicable for any building type. My building has a special concentrically braced frame lateral system. I would really like to construct the fire wall out of metal studs with gyp and avoid making it a structural wall that is also now a part of my lateral system. I have a hard time accepting that the fire wall should dictate what makes up my lateral system...
If you are talking a true firewall and not a fire separation, you likely need a dual wall, one attached to each side of the two 'separate' buildings. The firewall creates the two separate buildings. The wall has to remain intact in the event the other building collapses due to fire. Else go with two separate drywall rated walls and not use them laterally. The construction in these environs is denoted as 'shaftwall construction'.
Dik
Dik
paddingtongreen
Structural
dik's post ties in with my experience. I once built a free standing firewall that allowed the buildings to fall away on either side, leaving it to protect the other.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
A free standing firewall should not be used unless it can resist negative pressure following the collapse of the building on the fire side. The firewall must act as a cantilever from ground level, not easily achieved for buildings more than one story in height. It would be cheaper to use a double firewall, each attached to the building on one side.
BA
BA
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- #13
This is what I am hearing:
Don't do fire walls in multi-story construction, particularly in high seismic areas.
If you do have a fire wall in multi-story construction, you really need to have 2 buildings; which means 2 fire walls and a seismic joint between.
Don't do fire walls in multi-story construction, particularly in high seismic areas.
If you do have a fire wall in multi-story construction, you really need to have 2 buildings; which means 2 fire walls and a seismic joint between.
That is one way to do it and probably the best way, but the cost is usually viewed as prohibitive by the owner/client.
I am not fully up to date on the requirements in the Canadian code, but I am looking at NBC 2005 User's Guide which has a section entitled "Commentary C - Structural Integrity of Firewalls". This commentary suggests four design approaches as follows:
1. Double Firewall
2. Cantilever Firewall
3. Tied Firewall
4. Weak Link Connections
The double firewall is undoubtedly the best but is expensive.
I have never used the cantilever firewall and as stated earlier, I doubt that it could be economically used on anything but a single story building.
I have used the tied firewall concept on a few occasions. In this approach, the structure on each side provides lateral support to the firewall and the structure is tied together in such a way that lateral forces resulting from the collapse of the structure on one side of the firewall are resisted by the structure on the opposite side. I believe it to be the most practical way to accomplish the desired objective.
I have never used weak link connections and, although approved by our code, I don't trust the system to function properly so I cannot recommend it.
BA
I am not fully up to date on the requirements in the Canadian code, but I am looking at NBC 2005 User's Guide which has a section entitled "Commentary C - Structural Integrity of Firewalls". This commentary suggests four design approaches as follows:
1. Double Firewall
2. Cantilever Firewall
3. Tied Firewall
4. Weak Link Connections
The double firewall is undoubtedly the best but is expensive.
I have never used the cantilever firewall and as stated earlier, I doubt that it could be economically used on anything but a single story building.
I have used the tied firewall concept on a few occasions. In this approach, the structure on each side provides lateral support to the firewall and the structure is tied together in such a way that lateral forces resulting from the collapse of the structure on one side of the firewall are resisted by the structure on the opposite side. I believe it to be the most practical way to accomplish the desired objective.
I have never used weak link connections and, although approved by our code, I don't trust the system to function properly so I cannot recommend it.
BA
paddingtongreen
Structural
I had to go deep in the memory banks.
The free standing wall was reinforced concrete and the client's choice, it was for a stacker crane warehouse storing extremely volatile and sometimes explosive materials (cans of volatile liquid becoming overheated in the fire and bursting).
On a shopping mall, we put an expansion joint over an exit corridor with combination firewall/shear walls on either side. The steel (cantilevered top chords of the joists) did not connect in the middle but the flooring and roofing expansion joints did.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
The free standing wall was reinforced concrete and the client's choice, it was for a stacker crane warehouse storing extremely volatile and sometimes explosive materials (cans of volatile liquid becoming overheated in the fire and bursting).
On a shopping mall, we put an expansion joint over an exit corridor with combination firewall/shear walls on either side. The steel (cantilevered top chords of the joists) did not connect in the middle but the flooring and roofing expansion joints did.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
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