1. #1
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    Default Structural collapse

    hey everyone. me and a few of my firefighting friends were having a disscussion about structural collapse. what i want to find out is how long must a structure burn before there is a threat of structural collapse? and what kind of things can you look for to know that there may be a collapse? thanks everyone. stay safe.

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    What type of building?
    Construction material?
    Fuel load?
    Fuel material?
    Size of fire/extension?
    Current ventilation?
    Sprinkler systems in place and operating?
    Lightweight construction or trusses?
    If it is a metal frame building, do the supports and beams have fireproofing?
    Are there firewalls?
    How old is the structure?

    I think each building will have a unique collapse determination based on the current parameters it is seeing.

    Short answer: 10 minutes?

    What to look for........ Things falling down around your head?
    Last edited by SWLAFireDawg; 01-29-2007 at 01:55 PM.

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    google " structual collapse of burning buildings " it is a great book that will offer you many answers.

    quick answers though.

    It will depend on the type of building and many other varibles. For starters and this is just the tip of the tip. A building of fire proof construction will have the least chance of collapse. Fire proof being concrete floors, ceilings and support structures. A building of LWT (leight wieght truss) will be the highest risk, some studies saying a collapse is possible with as little as five minutes of fire exposure to supporting members. Problem is fastening systems that only penetrate 1/4 of an inch into the truss, also fiberboard which is used a lot burns real hot and real quick. As for signs of collapse, they will vary by building construction, but don't just get fooled into thinking total collapse, what about para pits or decks or any other combination of things.

    There is a ton of info to be had on this subject. Please do yourself a favor and get a copy of the above book and share it with the persons in your station. It will help you a ton.

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    Your best bet is to find out how the structures in your district are built. As mentioned before truss, tgi, and poor construction can greatly speed up collapse.
    Know where the fire is, know the construction and if in doubt don't go in / under / ontop etc.
    Don't bet your life on "10 minutes till collpase" or some other rule of thumb.
    Modern building products also don't give the warning that you could have gotten from older buildings (sagging floor, etc.)

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    Quote Originally Posted by MEck51 View Post
    google " structual collapse of burning buildings " it is a great book that will offer you many answers.

    quick answers though.

    It will depend on the type of building and many other varibles. For starters and this is just the tip of the tip. A building of fire proof construction will have the least chance of collapse. Fire proof being concrete floors, ceilings and support structures. A building of LWT (leight wieght truss) will be the highest risk, some studies saying a collapse is possible with as little as five minutes of fire exposure to supporting members. Problem is fastening systems that only penetrate 1/4 of an inch into the truss, also fiberboard which is used a lot burns real hot and real quick. As for signs of collapse, they will vary by building construction, but don't just get fooled into thinking total collapse, what about para pits or decks or any other combination of things.

    There is a ton of info to be had on this subject. Please do yourself a favor and get a copy of the above book and share it with the persons in your station. It will help you a ton.
    Don't forget about the bow string truss... which can be, and in many cases is, much more dangerous than LWT construction. It isn't anywhere near as common as LWT, but when it starts to go it goes quick.

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    Learn to read whether the "structure" or "contents" are involved for starters. Fire or smoke showing from gable vents or through the roof, fire on multiple floors are some good indicators. Getting your dispatcher to regularly update the IC with time advisements is another good way to keep time from slipping by. BTW, if anyone gives you a failsafe way to predict it, ask him to pick the Powerball numbers for me this week.

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    Yeah, around here, if we see bowstring trusses, we will NOT be going on the roof and depending how far along the fire is we may not be going inside.

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    Read Chief Dunn's "Collapse of Burning Buildings".
    The information is presented in an easy to read manner and in detail.

    http://vincentdunn.com/dunn/books_videos/books2.html
    "If you put the fire out right in the first place, you won't have to jump out the window."
    Andy Fredericks,
    FDNY E.48, SQ.18
    Alexandria, VA F.D.

    Rest in Peace

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    Another variable to all the above mentioned is rehab of building. Someone could cut beams, supports or fire walls after construction. Also the contents or anything added to the building may cause a more rapid collapse. There is no good way to determine exactly when a building is going to collapse. If there is fire inside the building is being destroyed. Think safety

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    There's no quick and easy way to learn what you want to know. The late, great Francis Brannigan (RIP) wrote "Building Construction for the Fire Service" to be used as a tool for firefighters. There are some great photos and each type of construction is discussed along with the hazards.
    Tom

    Never Forget 9-11-2001

    Stay safe out there!

    IACOJ Member

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    Remember, building constructors are not our friends and drinking buddies. Construction material in 2007 is even lighter than what it was in 1997.

    No rule of thumb is good, but a good starting point: If it is a commerical structure during working hours, you have a good chance of making a good push and trying to knock it down. If it comes in at 2, 3 am...you have very limited time to make that push. Chances are the fire just didn't start itself and has made good headway prior to your arrival. Push in, cant reach the main body of fire, or your lines are having no affect, GET OUT.

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    I have seen buidings collpse that are not even on fire...so, if you had a fire in one of these building before they collapsed, who knows.

    As stated before: Read Chief Dunn's "Collapse of Burning Buildings".

    There is also a video set that goes with the book. Great info.

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    Quote Originally Posted by ADSNWFLD View Post
    Don't bet your life on "10 minutes till collpase" or some other rule of thumb.
    And if you do choos to bet your life on that theory I want you to factor these figures into the equation:

    1. Fire starts somewhere in the structure.
    2. Fire gets noticed by alarm system or human
    3. Alarm company or Human notifies dispatch
    4. Dispatch types it in the computer
    5. Dispatch puts out station tones and incident details
    6. In the volunteer world FF's jump in their cars and head for the station
    7. FF's staff the first due unit
    8. First due unit drives to house on fire

    If, for easy Firefighter math, we put 1 minute on each of those items, using the 10 minute rule of thumb, that building would be fair game for collapse anytime after 2 min. Unless of coarse you want to be in upstate NY right now where there is multiple feet of snowload on roof tops, or in Anytown, USA where the DIY homeowner did some renovations.

    Too many factors to give a hard and fast answer to that. Like the others said, trusses, TGI beams, previous fires, anything factors into it.

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    Just remember, Brown smoke coming from the attic area is bad. Brown Smoke is a by-product of the early stages of combustion involving untreated wood. Such as wood trusses, rafters, joists or OSB. When you see brown smoke coming from the gable ends, vents or eaves it means that the fire is up in the attic space.

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    Here's an example of how different construction methods/materials can significantly affect building collapse potential.

    http://faculty.sunydutchess.edu/wals...ES/trusses.htm



    Kevin
    Fire Lieutenant/E.M.T.
    IAFF Local 2339
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    "Fir na tine"

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