In the photo, something is taped to the beams in serveral locations, could they be stress/load sensors of some sort?
1.
Posted on 03/23/2008 7:36:56 PM PDT by george76
Old photos of the Interstate 35W bridge show two steel connecting plates were visibly bent as early as 2003 — four years before the span collapsed into the Mississippi River, killing 13 people.
Minnesota Department of Transportation officials declined to say when the state first knew about the bending in the pieces of steel, called gusset plates.
Two photos, part of a report issued earlier this month by the National Transportation Safety Board, reveal slight bends in gusset plates that hold beams together at two separate connecting points. The plates are in areas believed to be among the first points of failure when the span collapsed.
The NTSB's Office of Highway Safety confirmed that the bowing is part of the investigation into why the bridge collapsed Aug. 1, NTSB Chairman Mark Rosenker didn't comment on the photos, but has said the original design for the bridge specified steel for those and other gusset plates that was too thin.
NTSB spokesman Terry Williams told the Star Tribune the bowing is among "the many things that we are looking at as part of this investigation."
The newspaper said inspection records make no mention of repairs to the bending gusset plates.
Since the bridge's construction during the 1960s, the state highway department had increased weight on the bridge by adding a layer of concrete to the deck in 1977 and by installing concrete barriers in 1998. And the NTSB said last week that, at the time of the collapse, more than 191 tons of construction material had been piled over the bridge's weakest areas.
(Excerpt) Read more at news.yahoo.com ...
“Can’t wait till theymanage our healthcare.”
— — —
That will collapse for the same reasons as the bridge: Poor initial construction and eventual overload.
Cripe, and I used to be scared walking over the old Washington Avenue bridge, back in the ‘40’s. I just knew it was going to come down.
Incorrect. The article said “more than 191 tons of construction material had been piled over the bridge’s weakest areas.”
It did NOT say the “weakest point of the bridge.” Big difference between the weakest point (singular) and the weakest areas (multiple unstated locations).
That amount of bend did NOT “cause” the failure (speaking as a registered professional structural engineer). It was not even a very good warning.
They say that the original design was flawed (gussetts half the thickness of what they should have been). If so, why did the MNDot approve to add additional lanes a few years ago. Did they not check the calculations when they approved that?
If the original design was flawed, why did MNDot allow it to continue in service when half of the thickness of some of the gussetts were rust (presumably they were then only 1/4 the thickness they needed to be at that time). Didn’t they check the calculations?
If the original design was flawed, why did MNDot decide to redeck the bridge, which implies that they expected the bridge to last another 15 years before replaceement. Didn’t they check the calculations?
The people who made the later decisions were more responsible for the collapse than the people who did the original designs. The later people approved heavier loads and a longer life than they should have. It if VERY obvious that the later people DID NOT CHECK THE CALCULATIONS before they made their desisions.
They don’t look too bent, to me.
Now, that could do it....
Actually, I heard it reported that the plates were 1/2 as thick as they should have been for the bridge “as it was” when it was first constructed. So it was compromised from Day 1.
It was years ago, so they had plenty of chance to bend more, and in any case, “not looking too bent” doesn’t mean the plates weren’t severly overstressed. They might have not supposed to bend at all, in which case any bend at all would have been way too much.
Oh, I don’t disagree. The point I was making is that the bending is a lot less than the headline suggested.
“The point I was making is that the bending is a lot less than the headline suggested.”
When steel takes on a permanent bend under load, which is not in the original design as as illustrated in the posted photo, it is telling the observant something. Unfortunately, there were no observant, or they were ignored, over ruled, ad nauseam.
St. Cloud rerouting traffic after bridge closed
Inspectors found bowing gusset plates.
I wish you hadn’t posted that pic. Now the tin-foil hatters are going to start screaming that the bridge was collapsed by explosives triggered by Karl Rove.
you’re right, their probably C4 charges!
It looks like the gussets in the photo are on the topside of the truss. The ones that failed were on the bottom side of the truss. This had nothing to do with the failure.
These had to be in compression to have a slight bend like that. Fatigue breaks don’t happen in compression. They happen in tension. Of course, gussets in tension would not bend like that.
This means absolutely nothing.
good analysis
I agree
almost looks like the construction union got paid by the rivet
Or maybe Ben Mitchell.
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