Re: Why did the I-35W bridge collapse?

James Robinson <wascana@xxxxxxx> wrote:

larry_scholnick@xxxxxxxxx wrote:

This thread is for your best guess as to why the MN bridge fell. NTSB
says it will be months (perhaps a full year) before they have a
definitive answer, so all we can post is our own best guesses. Don't
bother tearing down other people's guesses - no matter how stupid they
seem; we can let them be judged by The Truth when it becomes known.

Fatigue failure of a weld, perhaps aggravated by corrosion, in an area
where inspection was difficult.

Good surmise, as MdDOT last inspected the I-35W bridge in July 2006, so
they were not behind on their inspections, and it may have been a place
where inspection was impossible without dissembling the area.

We should not rush to judgment, as the NTSB did -not- blame the highway
agency for the 1967 Silver Bridge collapse.

In the case of the 1967 collapse of the Silver Bridge, spanning the Ohio
River between Ohio and West Virginia (46 dead), the cause was very
subtle, as it took months to trace it to a single piece of metal in a
critical eyebar joint, which had been forged with a tiny, unnoticed
crack that weakened further with corrosion.

It is ironic that even if stricter inspection requirements had been in
place, the collapse of the Silver Bridge probably could not have been
prevented, because the flaw could not have been detected without
disassembly of the eyebar joint. A visual inspection of the pin
connections with binoculars from the bridge deck would not have been
sufficient. The problem lies with using materials that are susceptible
to stress corrosion and corrosion fatigue, and in designing structures
without redundancy.

--
Scott M. Kozel Highway and Transportation History Websites
Virginia/Maryland/Washington, D.C. http://www.roadstothefuture.com
Capital Beltway Projects http://www.capital-beltway.com
Philadelphia and Delaware Valley http://www.pennways.com
.

Relevant Pages

  • Re: Why did the I-35W bridge collapse?
    ... where inspection was impossible without dissembling the area. ... In the case of the 1967 collapse of the Silver Bridge, ... critical eyebar joint, which had been forged with a tiny, unnoticed ... crack that weakened further with corrosion. ...
    (misc.transport.road)
  • Re: All fall down
    ... No amount of money can prevent a structural member from failing due to ... That cannot be established without inspection. ... combination of stress and corrosion. ... existing knowledge about the materials in question in that type of ...
    (sci.research.careers)
  • Re: Any comments on Minneapolis Bridge collapse?
    ... but Wikipedia says there are are 700 such bridges. ... Let us suppose that the chance of I-35W collapsing in a 10 year period ... Aug. 1 collapse willing to place their professional reputation on the ... It seems quite clear that no inspection protocol can be tight ...
    (sci.electronics.design)
  • Re: Any comments on Minneapolis Bridge collapse?
    ... and reading the UofM report on their 2001 ... followed by slow collapse of the remaining ... Geraldo Rivera's show on Fox right now, has retrieved inspection ... match would come from the federal highway fund. ...
    (sci.electronics.design)
  • Re: Any comments on Minneapolis Bridge collapse?
    ... inspection, I owuld theorize that one of the south-side approach ... pulling the central steel-arch sections off its ... followed by slow collapse of the remaining now-overstressed sections. ... Transportation went on TV to talk about their "Inspections" of bridges here. ...
    (sci.electronics.design)