huangyhg

i-35w collapse
the first report from the public hearing:
under design? is that an isolate case (by one design firm and state dot), or it is a standard practice/detail adopt by many states/institutions? any comments?
underdesign is not a standard, it's a mistake.
i have long list of questions for ntsb to single out the "undersign" as the sole cause after it (the bridge) has been there for a long while. hello, bridge designers?
we need to look at the report. it could be possible that it was a fatigue failure. the gusset plate would be category d.
it would be interesting to see the report. looking at the collapse video at the time, the failure seemed to be quite symetrical. that is one of the things i do not understand. if the gusset plate 'went' i would have expected a non symetrical failure
all we can do is look at the actual report before making any engineering opinions. a yahoo report is really not proven to be accurate and the headline may not be accurate.
the collapse seemed to be somewhat symetrical, but the other elements may have tied things together in the short term until the similar conditions/weak pints were triggered.
dick
the preliminary reports issued earlier this year by the ntsb identified these same gusset as being underdesigned. it was not just one gusset, but rather at the same location on each side of each of the trusses. the plates were shown 1/2" thick, when they should have been considerably thicker. no design calculations were found for these gussets. likely a drafting error, not found in the checking process.
a successful design of the gusset plate could be made using 1/2" thick plates, if the other dimensions were correctly proportioned. (thickness is only one part of steel area calculation.)
i can't believe that actual gusset thicknesses were not checked over the years especially with inspections and urs report using lsd. again as noted elsewhere, the bearings may be the culprit.
in my reading of the urs report, i could find no mention of checking the gussets. i could have missed it, as the report is quite long.
in this bridge, to memory the gusset plate thicknesses varied from 1/2" to about 1 1/2". the ones which failed were some of the most heavily loaded, and were 1/2".

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