now we know what happened, final structural report....
IN.gov: Investigative Reports
The ISF Structure failure was due to the inadequate capacity of
the lateral load resisting system, which was comprised of guy
lines connected to concrete “Jersey barrier” ballast.
The ISF Structure was shown to fail at wind speeds lower than
those specified under even the most liberal provisions of
applicable building codes and reference standards.
The ISF Structure was shown to fail at wind speeds lower than
those specified under even the most liberal provisions of
applicable building codes and reference standards.
Calculations and in.situ physical testing determined the Jersey
barrier ballast system had grossly inadequate capacity to resist
both the minimum code.specified wind speed and the actual
wind speed that was present at the time of the failure.
Even if the ballast system had provided sufficient resistance,
the synthetic webbing ratchet straps and wire rope guy lines
used did not have sufficient strength to resist forces resulting
from the North wind case under the wind loads of August 13,
2011 that were of a smaller magnitude than the code.specified
requirements.
The technical information presented in the James Thomas
Engineering catalog is insufficient to adequately design a
structure such as the ISF Structure, yet there is no explicit
direction to engage the services of a licensed design
professional to analyze complex loading configurations or
conditions.
Structural analysis performed by James Thomas Engineering’s
structural engineer falls short of adequately addressing the
actual loading conditions of the Sugarland set and suspended
entertainment technology equipment for the 2010 show (for
which the structure was analyzed) or the code.defined
environmental loading conditions to which the ISF Structure
could be subjected.
There is no evidence of an engineering review of the “2011
Sugarland Rigging Plot” by a licensed design professional prior
to August 13, 2011.
Regardless of the inadequacy of the directions of James
Thomas Engineering’s structural engineer, Mid America Sound
Corporation’s installation of the ISF Structure deviated from the
directions provided in the calculations performed by that
structural engineer with regard to the lateral load resisting
system.