Boise Airport Hangar 7

[TigerGuy]

https://www.cityofboise.org/news/fi...veral-injuries-following-a-building-collapse/

Hangar under construction collapsed killing 3 and injuring more.

 

[Tomfh]

The particular failure that occurred (lateral buckling of slender beam under gravity load) would have been very unlikely to occur if all the documented bracing and sheeting was on

The hard rock failure involved deficiencies with the design itself. Spans that simply didn’t work.

 

[hokie66]

As far as I know, OSHA doesn't deal with building design, just workplace safety issues.

 

[waross]

Is this feasible?
With the top edges braced but the lower edges inadequately braced, could the wing force have displaced the lower flanges to the lee side?
With the flanges no longer in a vertical line, gravity would take over and buckle the beams.
With the flanges displaced in that manner, top flange to windward, would a gravity driven collapse overcome the force of the wind so that the beams collapsed into the wind?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[FacEngrPE]

The OSHA General Duty Requirements

Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees."

Each employer shall comply with occupational safety and health standards promulgated under this act.

Each employee shall comply with occupational safety and health standards and all rules, regulations, and orders issued pursuant to this Act which are applicable to his own actions and conduct.

From OSHA's point of view it does not matter if the lack of bracing is "contractor means and methods" or the supplier(s) of prefabricated steel. Per the construction dive posting cited by Sym P. le (Mechanical), lawsuits (wrongful death) have been filed (which OSHA is not party to) to address questions which include parts not supplied to approved drawings and specifications.

It is important to read the notes on the first page of the approved construction set. The approved drawings include only the permanent bracing, but not any of the erection methods and bracing.

 

[Tomfh]

It’s more complex when a structure is especially prone to instability, a fact the designers seem to have acknowledged by incorporating lifting support bracing.

If a beam can’t be lifted into position without buckling under its own weight, that’s not just a construction issue—it’s also a design concern.

 

[Sym P. le]

As best we can see, the diaphragm bracing (in the central portion of the structure) was not installed prior to the beam pairs being erected. This is likely an erection method issue as the braces could easily have been installed prior to lifting thus also eliminating the need for temporary bracing against that failure mode. Did the constructor just decide this for himself, did the engineer approve? Perhaps there was some miscommunication. This precludes any notion that the design was inadequate. Someone just didn't know what they were doing.

It's as though they lifted the first beam pair (lines 6 and 7) only to see them deflect, and then attempted to jury rig the subsequent beam pairs (against the first), none of which included any diaphragm bracing, hoping they could straighten the whole thing out later. Unfortunately, it would seem that any further structural members would just add to the misaligned mass and make things so much worse.

 

[Tomfh]

What do you mean the diaphragm beam bracing was not installed? It seems to have been installed between pairs of beams, in conjunction with the lifting support bracing?

 

[Sym P. le]

Only towards the corners/columns, not towards the building centerline. At least I can't plainly see it in any images. That's why the beams bowed between the east and west constraints. It's not buckling that initiated the collapse, rather lateral sway. Once the corners are sucked in, buckling happens.

 

[XR250]

Is it possible that is simply not reasonable to assume that a structure of this size with such slender members cannot be erected with the current pool of labor?
I can see a situation where the EOR gets sued for just this very reason.

XR250, can you explain a bit more, I'm not sure I understand what you are saying here.

I guess what I am trying to say is that this building is so unstable until it is completed that just relying on "means and methods by others" may be considered negligent. Honestly, this building looks to be barely stable even when completed.

 

[SwinnyGG]

relying on "means and methods by others" may be considered negligent

'Negligent' is a big word.. but I will say from a contractor's point of view, bracing during erection is critical enough for both safety and general success of the project that I personally would not proceed with a build like this without a clearly articulated temporary bracing plan, whether it came from the EOR or the vendor of the PEMB or whomever.

In my opinion, assessing a steel structure in each stage of assembly and designing appropriate temp bracing is way, way beyond the skill set of any general contractor that isn't themselves a structural engineer.

 

[WinelandV]

Too much of erection bracing comes down to how the building is erected (i.e. the means and methods). No PEMB manufacturer is going to give you that. No EOR (who likely only designed the foundations) is going to give you that. Part of the erector's job (and thus, fee) is the expertise/knowledge of how to get these up safely (or lacking that, going out and getting that knowledge/expertise).

Please note that is a "v" (as in Violin) not a "y".

 

[3DDave]

Is this structure much different than used elsewhere? I get the feeling that the erector has experience and that this may have exceeded that experience and they went past the limits of their understanding. It's also possible the designers were the ones, that the span was simply wider than they had done previously and they didn't perform a check that they had never needed before. It would not surprise me if wind loads during erection had been neglected.

 

[SwinnyGG]

Too much of erection bracing comes down to how the building is erected

Every time I've done big steel, the erection plan has been developed with significant participation from both the erector and the EOR. Granted, I've never done a PEMB on a scale this large. I've built a gigantic hangar, but it was not a PEMB. Several of the main span elements required multiple cranes to set.. no chance we would've just made up the bracing ourselves.

Granted, the realm of big PEMBs like this are a specialty.. maybe the guys that do this all the time have an internal process to handle dealing with the temp bracing design

 

[waross]

Before the cladding goes on the wind loads must be much greater.
Even full, as designed, bracing while suitable for a completed building would be unsuitable for the wind load on the partially erected building.
The question is;
Who is responsible for designing and constructing suitable temporary bracing?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Sym P. le]

As I noted earlier, the winds abated prior to the collapse so not a primary factor.

 

[Tomfh]

Every time I've done big steel, the erection plan has been developed with significant participation from both the erector and the EOR

Yes there comes a point where it no longer cuts it to put a note on the drawing saying that erection is the contractors problem.