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Everything's Gone

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That sucks. 3-story isn't exactly a high-rise, though; my house sort of counts as 3-story as it has a crows nest as the 3rd floor, and there are lots of 3-story houses along the beach front.

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I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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Sorry IRS... didn't mean to imply it was a highrise... but, we are leaning towards wood structures in excess of 10 storeys... a bit of a concern.

Dik
 
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Sorry for the misunderstanding.

Seems to me that any time humans build things, there's going to be possible problems; the thread about the high rise fire in London comes to mind. Possibly the curse of Icarus' ghost?

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This is only one example of hundreds of buildings built of wood frame construction that have destroyed people's lives. While many of these projects didn't have sprinklers in place (or not in the attics where the fire spread), they are a threat to not just one person, but to everyone that lives in the complex. For those that are interested there is a Facebook page devoted to this subject - search "Massive Fires Damage Lives". The page (not mine) has a compilation of major catastrophic fires such as the ones in Edgewater, NJ, Raleigh, NC, Los Angeles, etc.

And dik is right, there are some code changes promoted by the wood industry to use cross laminated timber (CLT) for high-rise structures. They passed the preliminary code hearings earlier this year, but will have a final vote in October. Even the International Association of Fire Chiefs has come out against CLT in high-rise structures.
 
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Often with fires like this it isn't the method of framing but the other materials used in construction.
The siding and roofing in particular.
I have seen large wooden structures burn, and I am amazed at how long they stand up, well after a steel building would have collapsed.

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Not exactly my area, but the dimensions of the base material obviously matters.
-Post and Beam type wood construction would natural use thick and heavy members, and they might last an hour or so.
-Wood trusses, typically built-up from thinner 2-by-x stick lumber, wouldn't last very long at all.

I presume that the same sort of thing would apply to heavy steel beams vs. trusses.

The point I'm trying to make is that it isn't just the material, but the surface area exposed (beam vs. truss).

The other points raised above are of course valid too.

 
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In most areas I've lived, BBQs weren't allowed on wood-based porches...

Dan - Owner
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A few years ago, my colleague and his wife and newborn son barely escaped this fire: Link

His work papers were destroyed and he was eventually forced to return to China temporarily until he could reestablish his identity and immigration status with the US government. Not sure if it turned out to be a design flaw or corner cutting by the contractor that allowed the fire to progress so rapidly, but I remember him telling me they had just seconds to run out before their apartment was consumed.
 
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VE1BLL said:
typically built-up from thinner 2-by-x stick lumber, wouldn't last very long at all.
Click to expand...

Wood I beams are another concern... a lot of surface area exposed and some of it quite thin.

Dik
 
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I understand from fire-fighting articles that there is more trust of large beam wood structures than steel. Even when the wood is on fire, one can see the dimensions of the wood and get a feel for remaining strength as wood doesn't tend to soften. With steel all bets are off, mostly because such thin sections of steel are used versus what wood would require. If it was only the structure, steel would win as it doesn't burn, but people fill their structures with fuel, so that part doesn't matter as much.

But for structures built of tooth-pick pieces and glue-lam, I wouldn't be so trusting.

 
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3DDave said:
I understand from fire-fighting articles that there is more trust of large beam wood structures than steel. Even when the wood is on fire, one can see the dimensions of the wood and get a feel for remaining strength as wood doesn't tend to soften. With steel all bets are off, mostly because such thin sections of steel are used versus what wood would require. If it was only the structure, steel would win as it doesn't burn, but people fill their structures with fuel, so that part doesn't matter as much.

But for structures built of tooth-pick pieces and glue-lam, I wouldn't be so trusting.
Click to expand...
Pretty much true but I'll elaborate.

Steel weakens drastically with heat and it will get hot quickly if expose to a decent fire. So if you have a beam lose 80% then you can imagine the results.

Timber will burn but only the timber that is expose to the air. It will charr and that charring will insulate and protect the inside from burning nearly as rapidly. The inside stays intact and maintains its structural integrity.


Of course if your building is based on toothpick then it will go up in flames like a good bunch of kindling. But if you have decently thick structural timber members then you can get impressive fire resistance out of them.

Glue-lam is fine if it is the good stuff. The good stuff has impressive fire ratings:

 
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Human909... your Young's modulus also decreases dramatically... another part of the problem. Charring helps, but I wouldn't rely on it for too long...

Dik
 
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Dik, wood burns at a predictable rate. So you can calculate an estimate for how long it will hold the load. Exposed part of the section of course doesn't have any stiffness, but unburnt core has much lower temperature. Charred layer will insulate the core always as it burns, you don't need to rely on anything.

Glulam_Arup_Interior_24-800x800-2.jpg


large-375430-woodbeam-fire-bentsteel.jpg
 
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Yes, I've had non-technical people balk at the idea that a wood framed building is considered fire 'resistant'. Granted, it might not be fire 'proof', but, as seen above, structurally, it may be able to survive better than a steel frame building. In fact, I had a veteran firefighter tell me once that if he had to enter a burning building, he feels safer inside a wood structure than a steel one, because as he said, the wood building will give you a warning when the beams are above to fail as you can hear them crack and splinter while a steel building will simply collapse with virtually no warning whatsoever.

John R. Baker, P.E. (ret)
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Not fire, that’s my understanding why Poplar is the preferred material for supporting mine tunnels. Not the strongest material, not the easiest to find or work with, or anything else like that. But rather because it fails slowly and noisily.
 
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For a timber framed hi-rise, it's not the main columns or beams that I'd be worried about as they are large and as stated above do fine.

It is the sense that the designers of such a building would then work their way through the load path and sequentially utilize smaller and smaller members....
Large framed girders supporting smaller beams and joists, supporting thinner decking, etc.
It can't all be heavy timber and still be as economical.

The codes, of course, may have provisions for fire protection for smaller sized members, but leave it to human nature to "forget" that the smaller members don't quite work as well and somehow, someway, didn't get properly protected.

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Moly... I'm aware that large timber has a little resistance due to the charring... but, if a fire is well developed and intense... it contributes to the load. Check the Glasgow School of Art recently...

Dik
 
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An interesting point of wood structures is that since they have 'some' delay, at least the ones with some cross section timber, the actual weight they have to support will be continuously decreasing as the fire progresses as all the contents vaporize and blow away or burn. Furniture and such probably burns four or five times faster than the structure so there will be a race going on.

Keith Cress
kcress -
 
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...and no live loading due to occupancy...

Dik
 
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