I-35W Collapse
I-35W Collapse
(OP)
The first report from the public hearing:
http ://news.ya hoo.com/s/ ap/2008111 3/ap_on_go _ca_st_pe/ bridge_col lapse_ntsb
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When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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RE: I-35W Collapse
RE: I-35W Collapse
RE: I-35W Collapse
RE: I-35W Collapse
RE: I-35W Collapse
RE: I-35W Collapse
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
RE: I-35W Collapse
RE: I-35W Collapse
RE: I-35W Collapse
RE: I-35W Collapse
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".
RE: I-35W Collapse
http://www.ntsb.gov/publictn/2008/HAR0803.pdf
Conclusion is that gusset plates were underdesigned at critical connections and led to the collapse.
RE: I-35W Collapse
... Which is not nearly as scary as the fact that the gussets buckled enough to notice, and enough to cause people to photograph them in 1999, and then they were left in service.
Mike Halloran
Pembroke Pines, FL, USA
RE: I-35W Collapse
As for the conclusion that this bridge fell due to underdesigned plates, I can only note that this was certainly a problem early on but thanks to many things done right in the design, it functioned and as steel should do, it gave warnings. The NTSB says that based on their interpretation of the inspection and rating codes no one had any reason to suspect a problem. It's this last sentence that I have a very difficult time with.
No engineer bridge or structural is going to wave off plate distortion like that especially when it coincidentally occurs at four of the same panel points through out the bridge.
It's much easier to blame a dead engineer and a defunct firm that to own up to poor maintenance. And what's worse is that our entire infrastructure is poorly maintained due to lack of funding....it's no secret and since 8/1/07 it shouldn't be shoved under the rug either.
Off my soapbox.
Regards,
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RE: I-35W Collapse
The way I understand it, there were new surfaces applied to the bridge, materials stored on the cantilever span and heavy equipment on an active span. To save a few bucks, the bridge loading was changed and no re-analysis was done.
It's a chicken bleep excuse to blame a 40 year old design, when you have whole state department of transportations employed to insure the road and bridges integrity.
RE: I-35W Collapse
Shortcomings in maintenance will never be completely eliminated, and I imagine that budget restraints will make the problem worse over time.
But if the gussets in this bridge were thick enough, we would not be having this discussion. Read all the reports and you will agree. Human error will never be completely eliminated either, but that should be our goal.
RE: I-35W Collapse
1) We use load factors for a very good reason - ultimately, we can't know exactly how much load a bridge will see, or how it will distribute. So we bump things up considerably, and design for that load.
2) Temperatures in Minneapolis that day were in the mid-to-upper 90s, which could easily produce higher loads. I wouldn't be surprised if temperature load had something to do with it, whether due to fatigue or some other loading.
3) I have "checked" structures that were designed according to older codes using newer codes and found them deficient. Yet, they're still standing.
It is conceivable, then, that a gusset plate could be underdesigned yet still support a bridge for 40 years.
RE: I-35W Collapse
It is not just conceivable, it happened.