Because steel bar joists are NEVER maunfactured wrong and masonry
construction NEVER fails, silly!
What happened here is a manufacturing defect and people are getting all up
on their hindlegs that the method of construction is wrong.
To further complicate this the building is in England, where there is the
possiblity that they do stuff different than we do here in the US.
The laminated flange was fine, it was the OSB web that runs in a groove in
the flange that came away.
The laminated flange is supposed to be stronger than raw timber and doesn't
shrink (well within 1% or whatever)
It sounds like the glue itself is where the problem lies.
Are you saying the web pulled loose from the (flange) bottom/top chords, or
that the web (OSB) disintegrated?
To me it seems like a lot of pressure is being generated downward and glue
alone is what holds it together and I find that sort of strange.
How long was the span, and how tall were the joists, and how were they
spaced (center to center)?
Yep. They use two and mix it directly before applying. They use two large
vats, It flows in and is mixed to the correct percentage and flow.
Something went wrong here. When mixed the surplus glue is amber coloured,
when not mixed correctly it is white.
Yep. the bottom.
The web was fine, just the glue.
420mm in depth. The span I'm not sure of. However it was in an area were
there was a lot of stress, however the beams should have easily coped.
What went first was the joint where the OSB web meets another section of
OSB. This went because the flange was not securely glued into the web. The
racking had gone. The vertical joint between the OBS pieces moved and the
whole integrity collapsed pushing out the bottom flange. It "may" have been
the case that is the OBS to OSB joint was in another position the beam would
have survived. The OSB to OSB joint was in an area near to the bottom flange
where the glue never took because it was not mixed correctly.
Boise, have a big problem in their manufacturing process. A good system
would have picked up that something is wrong - they are all computerised
with monitoring these days.
How many times has this happend in the past, and beams are fitted being a
ticking time bomb?
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