Poor design led to I-35W bridge collapse?

Most people did not expect it to collapse after 40 years, so the design lifetime was probably longer than that.

--=20

Anders Lager=E5s

Interesting old newsreel - but its replacement ALSO gallops when the wind blows a certain way. This is a difficult site, no doubt.

Brian Whatcott Altus OK

[bw] [rh]

And mentioned the existence of cracks (2001)

Brian Whatcott Altus OK

On Tue, 7 Aug 2007 13:02:12 -0700, "Matthew Beasley" wrote this to Robert Clark:

Without doing even trivial background research, I am tempted to say that the built up trusses give this the look of a bridge rather older than 40 years old, to my eye at least.

Brian W

Hmmm....1935, not the first of that kind, I wouldn't think

Brian W

I almost let this suggestion go in and out. But setting out a few survey camera tripod points round a structure for a yearly shot, would be just so cost-effective, it sounds like a winner.

Setup cost could hardly be more than $1,000 per bridge, and maybe $200 p.a per bridge. What's for a politician not to love about this one?

Shoulda patented the method, Dave!

Brian W

Strangely enough, people NEVER expect bridges to collapse, but they do anyway!

Brian Whatcott Altus OK

If you get rich and famous, and accidentally find yourself in Arridzona, buy me a coffee (if it is not over $2 per cup). I seem to recall mention of doing this with a single time-of-flight instrument, from a single location. Multiple locations will only improve / reduce the granularity.

It will only work if there is significant secular changes in the shape of the structure. I am not convinced there were, and I know we disagree here.

But the fact that corrosion can be so easily overlooked, or visual inspection in many places too difficult to perform...

*that* is where headway needs to be made. Short of hiring "Superman"...

David A. Smith

It is a very similar design to the I-35W bridge, down to the rather "pointed" joints connecting to the concrete supports. This is a two lane bridge with only 1/5th the traffic as the I-35W which probably helped it to survive 70 years:

Deception Pass Bridge.

I would still like to see how those joints look close-up. Do they have the same amount of corrosion at the joints and on the steel beams around the joints as was apparent on the I-35W bridge before the collapse:

Bob Clark

Looking more closely at that image you gave of the Deception Pass Bridge I would say the joints are actually more like the wider ones on the Desoto Bridge rather than the almost point-like ones on the I-35W.

Zoom in on the joints in these images:

Deception Pass Bridge

I-35W bridge. Desoto bridge. Remember pressure increases inversely as the *square* of the area. So a joint only 1/2 as wide would experience 4 times as much pressure on it.

Bob Clark

Dear Robert Clark:

two lane bridge.> I-35W bridge.>

eight lane bridge, possibly originally four. Now scale thebearing and concrete pillars up by a factor of two-to-four on theDeception Pass bridge, and compare them to I-35W again.http://dc.metblogs.com/archives/2007/08/minneapolis_i35.phtmlhttp://www.urbanplanet.org/forums/index.php?s=e81e03332c5cc1040893c91497e63229&showtopic=38175&st=0&p=767639&http://www.thisweek-online.com/2000/january/7burns.html...the original design appears to have been a 4 lane, with thedeck widened (to 6 then adding "HOV")later.http://www.johnweeks.com/bridges/pages/ms16.html... the bridge was being operated with failed bearings, placingthe structure in a bind. Additionally, it looks like all thetraffic was placed on one half the bridge, due to lanestriping... creating an off center load.Robert, I understand your position, but this appears to me tohave been negligence, not "poor design". Add to this the varioussolutions they tried for the persistent "black ice" problem...David A. Smith

That had been repaired. The hidden meaning in that is that someone in the state bridge maintenance program KNEW that the bridge had an ongoing problem with fatigue cracks and was satisifed that the patchwork repairs were adequate.

I don't think the joints themselves are pointed, The little pyramids are roofs to keep water and snow off the actual joint hardware, which, if it is built with the standards of the time, should be pinned pivots at one end and rollers at the other.

Ah.

Sadly, wrong. The Big Dig in Mass. is now spending monies on law suits. I'm beginning to think that this is part of a plan, but I used be paid to be paranoid.

Here there was not a murder indictment. (A lady was killed when the top piece of a tunnel just built smushed her.) Now the news is reporting that the cement used in the tunnels was watered down. WTF was the state chemists?

/BAH

This is something I know I know nothing about. Do they have to put pieces back together (like in airplanes) to do analyses?

Was it 8 (or whatever) lanes wide when it was built?

/BAH

Bridge

Correction. That should be pressure increases inversely with the area, which is as the square of the diameter. A support half as wide would undergo 4 times the pressure.

Bob Clark

Short Brothers built flying boats and on one new design the wings tore off at the wing root. The aeronautical engineers did the obvious thing and strengthened the wing roots. Again on take-off the wings tore off at the root. This time the engineers added braces between the wings but even that didn't work, so they added struts. Once again the wings tore off at the roots, and everyone was scratching the heads except the janitor. Overnight he borrowed a drill and without telling anyone drilled a line of holes along the wing roots. The next day the new plane took off and flew perfectly, and when it landed the engineers took it apart to see what was so different, and of course they found the line of drilled holes. An inquiry was held to find out how they got there and the janitor owned up, so they asked him how a lavatory cleaner would know the plane would fly. He said "In my experience nothing ever tears along the dotted line".

bridge.> I-35W bridge.>

lane bridge, possibly originally four. Now scale thebearing and concrete pillars up by a factor of two-to-four on theDeception Pass bridge, and compare them to I-35W again.http://dc.metblogs.com/archives/2007/08/minneapolis_i35.phtmlhttp://w......the original design appears to have been a 4 lane, with thedeck widened (to 6 then adding "HOV")later.http://www.johnweeks.com/bridges/pages/ms16.html... the bridge was being operated with failed bearings, placingthe structure in a bind. Additionally, it looks like all thetraffic was placed on one half the bridge, due to lanestriping... creating an off center load.Robert, I understand your position, but this appears to me tohave been negligence, not "poor design". Add to this the varioussolutions they tried for the persistent "black ice" problem...David A. Smith

Thanks for those links. On my reader the links got garbled. Here they are again:

Burnsville looks back at a rich history by John Gessner Staff Writer Posted 1/7/00

Minneapolis I-35W Bridge Collapse posted by Brownpau at 11:06 PM on August 01, 2007 Freeway history in your city. These all say the I-35W bridge was originally a 4 lane that was widened to an 8 lane, with the steel superstructure staying largely the same, and the concrete supports and joints unchanged. The design may have been adequate for a 4 lane with sixties traffic, but not for an 8 lane with 90's and 2000's traffic. However, I still don't like those point-like joints.

Bob Clark

Dear jmfbahciv:

I don't think they *have* to, but I think they *want* to look at every failed piece.

It looks like, from what I can find, it was 4 lanes wide at design (all lanes within substructure-width), was widened to 6 lanes later, and probably restriped to get the 8 lanes it had at time-of-failure.

David A. Smith