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Wood truss gusset plate failure example

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  • MalahatTwo7
    replied
    Originally posted by MemphisE34a
    MalahatTwo7,

    I have one half baked. The wife is 20 weeks. Due date is the end of April.
    Thats great news, although I've never heard it referenced like that before.

    Mtnfire, thats great news for you guys too. Glad to hear things are going well out in the Western World. LOL
    ----------------
    ON the origin of this thread, the following is an email message that came through the County yesterday regarding use of composite construction materials in flooring.

    Sent: December 5, 2006 7:55 AM
    To: 'FxCo Volunteers'
    Subject: [co02] all Caution Urged with Composite Floors

    All firefighters please read.

    This announcement by the IAFC is particularly important to safety. We have a lot of this kind of construction in the county.

    Jonathan, President, FCVFRA

    -----Original Message-----

    IAFC MEMBER ALERT: FOR IMMEDIATE RELEASE
    Contact: IAFC Communications Department
    703/273-0911 • www.iafc.org

    Caution Urged with Composite Floors
    Several Cases of Firefighters Falling Through Floors Have Been Reported

    Fairfax, Va., Dec. 4, 2006... The Safety, Health and Survival Section recently became aware of a potential hazard to firefighter safety. They asked the IAFC to share the following notification with all members.

    There have been several cases of firefighters falling through floors made of composite structural components and an even greater number of near-miss situations. This type of construction is being investigated as a contributing factor in a line-of-duty death.

    There is a proliferation of engineered floor systems in residential occupancies across the United States. Many newer residential occupancies incorporate lightweight, engineered wood or composite structural components, including trusses, wooden I-beams and lightweight flooring systems. In most cases, these systems are structurally sound and designed to support the appropriate loads under normal conditions; however, they are likely to fail very quickly under fire conditions.

    These components and systems are most often found in situations where applicable codes do not require any rated fire resistance between floor levels. They have much less inherent fire resistance than conventional wood joist floor systems and conventional wood decking. Remember – many codes do not require any fire resistance in residential floors!

    In the several cases of firefighters falling through floors, those floors had been exposed to fire from below for relatively short periods. Sometimes the weakened area is relatively small and the damage is concentrated to the area immediately above the seat of the fire. Firefighters should pay special attention when entering above a basement fire, where the floor could have been weakened to the point that the weight of a firefighter could cause a localized failure, dropping the firefighter into a burning basement. This can occur with no indication of imminent failure from above.

    Extreme caution should be exercised in any situation where entry is made above a basement fire. Conventional methods such as sounding ahead with a tool and checking for sponginess may not provide sufficient warning of a weakened floor. Using a thermal image camera is recommended to sweep the floor for hot areas before entering and to help avoid areas that appear to be hotter than the surrounding flooring. Be aware that thick carpets or tile floors may compound the risk by making it even more difficult to detect hot spots.

    In summary, members should consider the following regarding lightweight floor systems in residential occupancies:

    Know the local codes that require fire resistive construction and/or limit combustible storage in unprotected basements.
    Conduct pre-incident surveys of new housing developments to check the types of floor system being used.
    Use extreme caution when fighting basement fires in all occupancies, including newer residential occupancies.

    Work is being done by a number of our fire service partners to investigate this phenomenon and more information will be provided in the future. In the meantime, go to the following websites for more information:

    http://www.ksdk.com/news/news_articl...storyid=107868
    firefighterclosecalls.com/weeklydrills.php
    http://www.rapidintervention.com/med.../february2005/
    www.firenuggets.com/dunn2.htm
    www.cdc.gov/niosh/99-146.html
    -end-


    One of the fellows from 414 works construction and had some further comments, but I forgot to forward that message to the office. Will update further when I get home tonight.

    Leave a comment:


  • mtnfireguy
    replied
    Originally posted by MalahatTwo7
    Mtnfire, how are things in Wyoming these days? Haven't heard nor seen ya in a long time!
    Things are well here, building a new main fire station (finally), had a really busy wildland season this summer now we are for winter to set it!

    Leave a comment:


  • johnny46
    replied
    Originally posted by mtnfireguy
    Excerpt from: http://www.ladderconcepts.com/Ladder...tesPostive.pdf


    Unfortunately, the fire service seems to have been focused on a few "urban myths" about building construction, most notably, gusset plates and lightweight trusses. It has been touted that these connectors curl up and pop off when they get hot. We have yet to see in our 60 years of experience, a gusset plate curl, pop, jump or anything else, when they are heated. What our research and experience has told us is the wood is burning away from the plates, a concept we have been teaching for nearly five years.

    We have also not seen trusses collapsing or failing because of one component failure, or one gusset plate burning off in a truss. The building component redundancy provides surprising resistance to catastrophic sudden collapse. This is not to say that any one component failure is not significant, especially if one is standing on that failed component. In many instances, buildings that have been said to have had truss collapse have, in fact, suffered sheathing failure. We have taught repeatedly that, all things being equal, the sheathing will burn through far earlier than the trusses will fail.
    I'm glad these two guys have been lucky. Excellent. Wonderful.

    It's great that they have had this experience and I'm very happy for them.
    Last edited by johnny46; 12-05-2006, 06:40 PM.

    Leave a comment:


  • MemphisE34a
    replied
    MalahatTwo7,

    I have one half baked. The wife is 20 weeks. Due date is the end of April.

    Leave a comment:


  • MalahatTwo7
    replied
    HEY MEMPHIS
    Your speech about going home and being safety susie are well taken, I have 2 1/2 kids myself, but I say again:
    What did you do with the "Other 1/2"?

    Mtnfire, how are things in Wyoming these days? Haven't heard nor seen ya in a long time!

    Leave a comment:


  • MG3610
    replied
    Originally posted by MemphisE34a
    Thats not the problem, thats a good thing. In most construction that uses gusset plates, the wood will burn up before it fails and falls. Large open spans are the only thing you really need to worry about, but I see or hear of chiefs not letting people go into houses where the attic is involved, because the roof may fall.

    I call BS. Home and apartment roofs burn up. They very rarely completely fall down due to fire.

    Quit coming up with excuses and go inside and put the fire out.
    Amen to that!!!!

    Leave a comment:


  • mtnfireguy
    replied
    Excerpt

    Excerpt from: http://www.ladderconcepts.com/Ladder...tesPostive.pdf


    Unfortunately, the fire service seems to have been focused on a few "urban myths" about building construction, most notably, gusset plates and lightweight trusses. It has been touted that these connectors curl up and pop off when they get hot. We have yet to see in our 60 years of experience, a gusset plate curl, pop, jump or anything else, when they are heated. What our research and experience has told us is the wood is burning away from the plates, a concept we have been teaching for nearly five years.

    We have also not seen trusses collapsing or failing because of one component failure, or one gusset plate burning off in a truss. The building component redundancy provides surprising resistance to catastrophic sudden collapse. This is not to say that any one component failure is not significant, especially if one is standing on that failed component. In many instances, buildings that have been said to have had truss collapse have, in fact, suffered sheathing failure. We have taught repeatedly that, all things being equal, the sheathing will burn through far earlier than the trusses will fail.

    Leave a comment:


  • FWDbuff
    replied
    Originally posted by CaptainGonzo
    The truss may be damaged at any time... from the moment it leaves the factory to the moment it is nailed in as part of the lightweight roof support system. All we can do is hope that the local building inspector checks out everthing dealing with lightweight construction when they do the rough carpentry inspection phase of building approvals prior to occupancy.
    I know. I am one of the local building inspectors! Hence my comment to the gentleman regarding modifying the engineered truss. Anytime I find a modified or damaged/broken truss, builder is automatically required to produce a signed/sealed repair/modification report (as required by the Building Code.) The cut sheets are usually signed by the Mfr's engineer at the plant. When one is damaged out in the field, a repair report signed by any design professional is acceptable- that the new DP is accepting the responsibility of specifying the repair of another (the original) DP's designs.
    Last edited by FWDbuff; 12-04-2006, 04:49 PM.

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  • Catch22
    replied
    Originally posted by Rescue101
    If it's raining plates,I'm moving to another area.If you guys wanna believe lightweights burn "up and out"have at it.Under the remains isn't my idea of a good time.Of course the snow load up here can have quite an effect on the gravity side of the issue.And it isn't just the roof you got to watch on the lightweights,it's what's holding up you feet;or knees if you're doing it right.As Elmer would say:Be veeeewwary careful around these. T.C.
    Or what's resting on those trusses in the attic. I've seen engines in attics, among a number of other heavy things that could come crashing through.

    Leave a comment:


  • Rescue101
    replied
    If it's raining plates,I'm moving to another area.If you guys wanna believe lightweights burn "up and out"have at it.Under the remains isn't my idea of a good time.Of course the snow load up here can have quite an effect on the gravity side of the issue.And it isn't just the roof you got to watch on the lightweights,it's what's holding up you feet;or knees if you're doing it right.As Elmer would say:Be veeeewwary careful around these. T.C.

    Leave a comment:


  • CaptainGonzo
    replied
    Originally posted by FWDbuff
    Is that approved by a registered design professional (IE Structural Engineer or Architect?) If not you could be opening yourself up to a massive liability. Check the cut sheet that comes with each truss- they are signed and sealed by an engineer, and it specifically states on them, that any modification thereof will void any warranties and/or performance guidelines.
    The cut sheet may be "signed and sealed" by a professional engineer who designed the truss, but you can be damn sure he wasn't in the factory at the time it was built.

    He wasn't there when it the trusses with his name and seal on the cut sheets were loaded onto a flatbed truck.

    He wasn't there when the trusses were unloaded at the lumber yard, reloaded onto another flatbed and delivered to the job site.

    The truss may be damaged at any time... from the moment it leaves the factory to the moment it is nailed in as part of the lightweight roof support system. All we can do is hope that the local building inspector checks out everthing dealing with lightweight construction when they do the rough carpentry inspection phase of building approvals prior to occupancy.
    Last edited by CaptainGonzo; 12-04-2006, 03:44 PM. Reason: correction of spelling errors

    Leave a comment:


  • PATF1engineer
    replied
    I am more worried about going through it then it falling on me. I agree that a total collapse may be unlikely. But being aware of this situation is going to make me think a little harder about getting on the roof without a roof ladder or working off an aerial to do ventilation. Or even changing tactics to avoid the roof altogether. If that makes me a safety susie then so be it.

    Look, the fire service can bitch about these things all they want, but they are not going away. Being aware of this type of construction and other types of lightweight construction and using smart tactics are the only way to deal with them.

    And I am not a chief, just a glorified peon.

    Leave a comment:


  • MemphisE34a
    replied
    Maybe you need to re-read my post. I stated that in houses and apartments roofs will burn up and away before a complete system fails. Even if a section were to fall, you have the interior walls that will prevent a complete pancake style collapse.

    You have proven my point even better than I could have. You apply a lesson you have learned, in this case a roof collapse in a church (wide open spaces) here in my hometown that killed 2 firefighters over 15 years ago when the entire roof system did fail and pancake style collapse due to the lack of interior walls to all situations with truss roofs and gusset plates.

    Your speech about going home and being safety susie are well taken, I have 2 1/2 kids myself, but I say again:

    Lightweight construction in dwellings and apartments with load bearing and non-load bearing interior walls and a lack of wide open spaces will burn up and away before they fall down.

    And just for the record, I am not trying to pick a fight either.
    Last edited by MemphisE34a; 12-03-2006, 10:51 PM.

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  • PATF1engineer
    replied
    Not looking to start a fight, but....

    Originally posted by MemphisE34a
    Thats not the problem, thats a good thing. In most construction that uses gusset plates, the wood will burn up before it fails and falls. Large open spans are the only thing you really need to worry about, but I see or hear of chiefs not letting people go into houses where the attic is involved, because the roof may fall.

    I call BS. Home and apartment roofs burn up. They very rarely completely fall down due to fire.

    Quit coming up with excuses and go inside and put the fire out.
    Not quite sure what you are getting at here. I don't think that exercising some discretion and conducting operations in a smart manner based on the type of construction and the fire conditions falls under the area of making excuses. I would never advocate letting a building burn because of the type of construction. But you better believe I am going to factor in that information before I put myself or my people at undue risk. If, in my and the other officers judgement, we can do that operation relatively safely, you better believe we are going to do it. However, going home to my family, and seeing to it that the people working with me do the same, is a hell of a lot more important then trying to prove how mush of a hero I can be by doing something blatenly unsafe.

    There is more then enough information out there on issues involving lightweight construction, including some that should hit pretty close to home for you.

    http://www.interfire.org/res_file/pdf/Tr-069.pdf

    I would never advocate cowardace or excuse making on the fire ground. But ignoring potential safety issues related to building construction is stupid.

    Leave a comment:


  • DonSmithnotTMD
    replied
    Originally posted by MemphisE34a
    Thats not the problem, thats a good thing. In most construction that uses gusset plates, the wood will burn up before it fails and falls.
    No kiddin? It looked cheesy to me, but I've never built anything big. Anyway, that's why I asked -- thanks. Doesn't look like anybody around here uses that method anyway.

    oh yea, I found this -- http://www.cdc.gov/niosh/docs/2005-132/
    Last edited by DonSmithnotTMD; 12-03-2006, 12:46 PM.

    Leave a comment:

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