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PEMB Construction Collapse in Argyle, TX 1
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msquared48
Structural
Bracing... bracing... bracing.
Mike McCann, PE, SE (WA)
Mike McCann, PE, SE (WA)
TXStructural
Structural
Time and again, safety during construction is not part of a design and the constructors are left to decide what bracing is needed. Or more precisely, the EOR doesn't have responsibility for means and methods, and the person doing the 'pre-engineering" of components or a system doesn't have the information required to design the bracing (that is, how bracing carries forces back to the rest of the structure or the ground.) In the wood truss industry, many (most?) suppliers do not show in-process bracing. I suspect the same applies to some PEMB. OSHA does have some coverage on this.
Frequently, I hear from contractors that "the engineer over-designed this thing and it would be fine with half this much reinforcement." We, as designers, need to do a better job of interacting with contractors so they respect our designs, and when we do indicate bracing they abide by it. I would guess that the erector has used these same techniques previously with success. What I do not understand is why the permanent lateral bracing on the sidewalls was not installed before the roof purlins were being set. It seems like it would have been difficult to true up the building and keep it that way. Sad as it is, better that this happened now than when it was occupied if the bracing was simply forgotten. (We obviously don't know the circumstances yet, but lack of adequate bracing seems to be the obvious culprit.)
I have been working with a construction engineering program at a nearby university. These student will be uniquely positioned to help reduce these problems. Their curriculum is half structural engineering and half construction management. I guess I should discuss this example with the professor since it is so near. (I rode past this high school on Tuesday.)
Frequently, I hear from contractors that "the engineer over-designed this thing and it would be fine with half this much reinforcement." We, as designers, need to do a better job of interacting with contractors so they respect our designs, and when we do indicate bracing they abide by it. I would guess that the erector has used these same techniques previously with success. What I do not understand is why the permanent lateral bracing on the sidewalls was not installed before the roof purlins were being set. It seems like it would have been difficult to true up the building and keep it that way. Sad as it is, better that this happened now than when it was occupied if the bracing was simply forgotten. (We obviously don't know the circumstances yet, but lack of adequate bracing seems to be the obvious culprit.)
I have been working with a construction engineering program at a nearby university. These student will be uniquely positioned to help reduce these problems. Their curriculum is half structural engineering and half construction management. I guess I should discuss this example with the professor since it is so near. (I rode past this high school on Tuesday.)
>>>Time and again, safety during construction is not part of a design and the constructors are left to decide what bracing is needed.<<<
>>>Frequently, I hear from contractors that "the engineer over-designed this thing and it would be fine with half this much reinforcement." We, as designers, need to do a better job of interacting with contractors so they respect our designs, and when we do indicate bracing they abide by it.<<<
TXStructural, respectfully, in the first scenario the engineer is being held responsible for not providing enough information and in the second scenario he’s being held responsible for the contractor not believing the information he provided. It seems he can’t win.
>>>Frequently, I hear from contractors that "the engineer over-designed this thing and it would be fine with half this much reinforcement." We, as designers, need to do a better job of interacting with contractors so they respect our designs, and when we do indicate bracing they abide by it.<<<
TXStructural, respectfully, in the first scenario the engineer is being held responsible for not providing enough information and in the second scenario he’s being held responsible for the contractor not believing the information he provided. It seems he can’t win.
I agree with Archie on this.
If we had to design bracing for a PEMB, it would be so complex and expensive, no one would ever consider it.
Additionally, the liability would be huge as most accidents occur during construction.
While this is a certainly an unfortunate incident, I feel means and methods should be left to the contractor.
If we had to design bracing for a PEMB, it would be so complex and expensive, no one would ever consider it.
Additionally, the liability would be huge as most accidents occur during construction.
While this is a certainly an unfortunate incident, I feel means and methods should be left to the contractor.
JedClampett
Structural
It's not like the PEMB industry hasn't assembled a couple hundred thousand of these. Don't they have procedures on how to do it safely? I know the joist guys have tons of rules on tieing off and other safety procedures.
The design engineer has minimal involvement in the PEMB. When we do one, we write a specfication and give physical dimensions. The rest is delegated.
I suspect that this was either due to working in too strong of winds or one of those lift operators jarring the frames.
The design engineer has minimal involvement in the PEMB. When we do one, we write a specfication and give physical dimensions. The rest is delegated.
I suspect that this was either due to working in too strong of winds or one of those lift operators jarring the frames.
TXStructural
Structural
Archie, we agree on this, but someone needs to take responsibility. When parts are designed and other parts are delegated and there is insufficient integration or coordination, we end up with a failing elevated, hotel walkway. The financial incentives for the parties should result in us fixing the deficiencies, if not for insurance and lawyers insulating us from the pain.
Jed, I certainly hope we are not willing to accept that normal design winds (probably not an issue in this case) or incidental contact by a lift (which should be anticipated) will result in a fatal collapse during construction.
It is completely unacceptable to concede that fatalities will happen in the course of someone's job on a construction site. What we build is not important enough to allow it.
I also think it is probably excessive to point to an industry ("the PEMB industry") until we establish that the contractor here was adhering to industry standards. It may be that there is no industry standard, or it may be that the contractor deviated from them. If neither is to blame, then the industry standard is obviously not sufficient. Unfortunately, we may never really know unless OSHA intervenes. (Being a local government project, I'm not sure they will.)
Jed, I certainly hope we are not willing to accept that normal design winds (probably not an issue in this case) or incidental contact by a lift (which should be anticipated) will result in a fatal collapse during construction.
It is completely unacceptable to concede that fatalities will happen in the course of someone's job on a construction site. What we build is not important enough to allow it.
I also think it is probably excessive to point to an industry ("the PEMB industry") until we establish that the contractor here was adhering to industry standards. It may be that there is no industry standard, or it may be that the contractor deviated from them. If neither is to blame, then the industry standard is obviously not sufficient. Unfortunately, we may never really know unless OSHA intervenes. (Being a local government project, I'm not sure they will.)
OSHA will be involved on any fatality like that. The government entity's employees may not be covered under OSHA (not sure about that), but the construction company sure is (and I'm assuming that was an employee of the erection company, and not, say, an inspector, that was killed). OSHA publishes information on a lot of accidents, so this one may or may not have more information out in a year or so.
TXStructural
Structural
From my Twitter feed: Argyle FD confirms that there has been another fatality on the same construction site as the collapse last week at Argyle HS.[pre][/pre]
While surfing around on Youtube, I ran across a series of "disaster" videos that are fairly interesting, and short enough not to kill an evening. This particular one reminded me of the post here, although it doesn't seem to be related in its causes:
Look on the "related videos" list for the others.
Look on the "related videos" list for the others.
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