Delaware River Bridge Closure 4

[ImminentCollapse]

http://www.enr.com/blogs/11-mid-atl...8-large-fracture-closes-delaware-river-bridge

Looks like a deck truss. Must be continuous near this location for the top chord to fracture.

IC

 

[bridgebuster]

The approaches for the bridge are continuous trusses. I read the story in my local paper over the weekend but the report didn't identify a location on the bridge. Assuming it's over a support, and given the age(notice the rivets) I'd guess brittle fracture.

 

[Lomarandil]

http://www.philly.com/philly/busine...take_may_have_caused_bridge_beam_to_fail.html

(TLDR) Karl Frank, professor emeritus UT Austin suggests fracture due to a bad plug weld on mis-drilled holes (during fabrication).

 

[BridgeEI]

He must have a better picture because I can't see anything regarding his suggestion. OF course it probably looks better on a computer than iPhone...

 

[Lomarandil]

If you zoom way in, there do appear to be two regions of discoloration in line with the bolt holes further down the member.

That said, Mr. Frank is a bolder man than I to come to that conclusion so quickly.

 

[JAE]

Here's the photo - you can see irregularities in the edge along the fracture that are in line with the bolts further down:

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[Teguci]

My first question when I saw the photo was "Why did the crack propagate there?" I would have expected it at one of the holes.

Lomrandil - star for posting an article with a reasonable answer. Thanks!

Looks like the crack is offset from where the holes would theoretically be.

 

[JAE]

Teguci - that's what I was thinking - there definitely is an irregularity at the fracture in line with the bolts/rivets.

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[bridgebuster]

A brief report from FHWA.

 

[BridgeEI]

Very interesting report. I wonder who the consulting engineer is, or if there are a couple involved for all the testing, design, inspection.

That's amazing that the paint contractor hears a loud pop, the bridge shakes, then proceeds on as if nothing happens and either doesn't notify the resident engineer or the engineer doesn't move quick on it.

These structures have more redundancy than we give them credit for. But who knows what element is paying the price to keep it up.

 

[hokie66]

Yes, it must have been a hell of a bang, and negligent not to report it.

Redundancy/continuity saved the bridge. Interesting, and counterintuitive to me, that the top chord on the other side went into compression.

 

[BridgeEI]

I have a hard time picturing it going to compression also but may make more sense if I saw the plans/details. I would think if it went to compression there would be more problems but maybe that's the strengthening the author discusses.

 

[bridgebuster]

Finally had a chance to read the memo. HNTB is one of the consultants for NJTA, see Figure 5.

I noticed they considered this a brittle fracture.

When you think about it, right now they have two - two span trusses instead of a 4 span truss.

 

[Lomarandil]

I'd like to think that I'd report a bang as loud as that -- but you hear a lot of sounds when working under an active bridge.

Especially if the final fracture area was only a small portion of the total section (hence the energy/sound was less) -- I might not have thought too much of it if it wasn't related to the work I was doing (e.g painting).

 

[OSUCivlEng]

Looks like they will try to jack it back into place starting today.

http://www.burlingtoncountytimes.co...cle_9167da59-68ea-5ab4-8cca-a9dcd2495370.html