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Re-Imagining Wood Challenge

Flammability as Fire Protection

This topic contains 22 replies, has 7 voices, and was last updated by Profile photo of ivan starr ivan starr 1 year ago.

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  • #2326
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    D Gaker
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    Wood structures are often perceived as being vulnerable to damage by fire.  However, due to the process of turning the exterior of timbers to insulating charred material, large members often survive quite well in structure fires.  This allows the building to stand longer, facilitating escape, rescue, and salvage of the structure or at least the materials.

     

    The problem is that this is not well understood or incorporated into building codes.  This project aims to collect available knowledge about performance of large timbers in fires, outline research areas, and provide for sharing of resources with building officials.

    [starrater tpl=44 size=’30’]

    TimberFrame-Fire

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  • #2328
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    D Gaker
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    With a greater understanding of how heavy timbers perform in fires, it will be possible to build much larger buildings with wood.

     

    http://inhabitat.com/wood-innovation-design-center-construction-set-to-begin-on-north-americas-tallest-wooden-structure/

    #2329
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    D Gaker
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    I remember hearing somewhere that large timbers used in structures were originally given beveled edges as a way to prevent flames from spreading.  Does anyone know of a reference for this?

    If you look closely at the attached picture, you can see the small bevel I’m talking about.

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    #2334
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    D Gaker
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    In this picture you can see that the smaller pieces of wood (siding) are burning very quickly while the structure still stands due to the fire not penetrating to the core of the large timbers.

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    #2345
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    ciscolara
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    So whats your idea? your proposal?

    #2346
    Profile photo of D Gaker
    D Gaker
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    My proposal is to collect the available information, find out what research needs to be done, and revise building codes to accommodate the phenomenon of large timbers self-insulating in structure fires.

    #2360

    The point with bevelling edges is that sharp edges will catch fire much more easily. You can observe this when you are sitting at a campfire. If you put splitted wood with the sharp edge directly on the fire they are going to burn relaitvely fast. But if you lay the piece of wood with its flat side into the flames, it takes recognisably longer.

    The same effect will appear on your planks and beams in a house.

    I think this can be referred to the fact that at a sharp corner you have puntually a lot more oxigen surrounding the wood particles, what makes the wood burn at this point more easily. Also the heat cannot be conducted so well by the wood in this area as it could be on a flat surface so the inflammable gases in the wood evaporate faster. It is a bit tricky to describe what i mean, but i hope you can make it out even with my imperfect english.

     

    #2365

    The chamfered edge is less flammable because it takes longer for the material to heat up and release the combustible gasses. The least flameable shape is obvious a cylinder (log) and the closer you get to that shape the better. Wood doesnt actually burn, when it reaches a certain temperature it releases gases and then those ignite when they reach their flash point.

    This technique of charring wood has been around for hundreds of years, primarily used in shoring for mining shafts and tunnels.

    When talking about saving buildings from burning down and collapsing, wouldnt it be far more beneficial to address the exterior and interior of the building , not the bones. Because by the time a fire reaches the bones, the house is a write off already along with anyone that is inside.

    This may be best suited for decks and exterior structures. Because quite often it is a deck that catches on fire and then burns the house down.

    #2373
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    D Gaker
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    Does anybody know of research indicating the difference beveled edges makes?

    I’d like to eventually have things like this incorporated into building codes to make it easier to build with timber.  Currently, anyone looking to build a structure of large timbers has to build the arguments alone.

    I even checked the wood handbook, but I didn’t find anything to reference about flame spread by type of edge treatment, not to mention by dimension of lumber.

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    #2379

    Although not specific to beveled edges, perhaps the following could help:

    Mačiulaitis, Romualdas; Jefimovas, Andrejus; Zdanevičius, Povilas. Research of natural wood combustion and charring processes.  Journal of Civil Engineering & Management. 2012, Vol. 18 Issue 5, p631-641. 11p. 1 Illustration. DOI: 10.3846/13923730.2012.720935.

    #2389
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    D Gaker
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    This is a fantastic place to start.  Thank you!

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    #2398
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    D Gaker
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    This looks like an awesome resource, but it is terribly organized.

    http://www.mace.manchester.ac.uk/project/research/structures/strucfire/materialInFire/Timber/

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    #2404
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    D Gaker
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    I’ve found a good resource from a fire department’s perspective.

    I’m hoping that, through my research, I can collect as much of this information and understanding as possible, identify what is poorly understood about how structures of large timbers perform in fires, and eventually to influence building codes and protocol for fire departments.

    #2405
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    D Gaker
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    The file was too big.

    Here’s the link.

    http://www.firehouse.com/blog/10459679/ordinary-and-heavy-timber-constructed-occupancies-training-download

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    #2410
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    ciscolara
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    I like the idea. you are trying to understand as much as you can how wood takes fire. but isnt a natural thing for wood to burn?

    #2415
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    D Gaker
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    That is exactly correct!

    Wood does naturally burn, and in many situations (like wood structures), that is seen as a bad thing.  My argument is that it might actually be good that wood burns because that process can protect the interior of the beams and columns.  However, this phenomenon is not considered when building codes are written.

    With a better understanding of how timber structures perform in fires, this seemingly bad attribute of wood might be used to create safer structures.

    http://hylandtimberframing.com/services-and-timber-framing-info.html

    http://forum.lowyat.net/topic/2299776/all

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