https://www.youtube.com/watch?v=e8PodEM4Y8g&ab_channel=BreakingPointsBreakingPointsVerified

An interesting video about a structural failure on a large bridge which crosses the Mississippi River. The defect was only picked up last month, luckily before it became catastrophic.

Bloody engineers!

sibeen said:

https://www.youtube.com/watch?v=e8PodEM4Y8g&ab_channel=BreakingPointsBreakingPointsVerified

An interesting video about a structural failure on a large bridge which crosses the Mississippi River. The defect was only picked up last month, luckily before it became catastrophic.

Bloody engineers!

“To the inspector who bypassed his boss, bypassed his client, and went directly to 911 to get the bridge shut down ASAP… your efforts to pass the Engineering Ethics course paid off, right there!”

Bloody engineers :)

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

The Rev Dodgson said:

sibeen said:

https://www.youtube.com/watch?v=e8PodEM4Y8g&ab_channel=BreakingPointsBreakingPointsVerified

An interesting video about a structural failure on a large bridge which crosses the Mississippi River. The defect was only picked up last month, luckily before it became catastrophic.

Bloody engineers!

“To the inspector who bypassed his boss, bypassed his client, and went directly to 911 to get the bridge shut down ASAP… your efforts to pass the Engineering Ethics course paid off, right there!”

Bloody engineers :)

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

Yeah, that’d be right, put all the sorting of this shit out onto the electrical mob :)

Yeah, I subscribe to that channel too. Quite worrying that such a thing could do for long.

The Rev Dodgson said:

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

How is that done?

They use drones to inspect them these days.

Spiny Norman said:

The Rev Dodgson said:

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

How is that done?

One way is to attach audio sensors at regular intervals, and listen for warning noises.

Video cameras all over the place would also seem to make sense, but I don’t know if anyone actually does that.

The Rev Dodgson said:

Spiny Norman said:

The Rev Dodgson said:

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

How is that done?

One way is to attach audio sensors at regular intervals, and listen for warning noises.

Video cameras all over the place would also seem to make sense, but I don’t know if anyone actually does that.

What about some sort of reflectors and laser measurement?

Peak Warming Man said:

They use drones to inspect them these days.

red light flashes in Creswick

party_pants said:

The Rev Dodgson said:

Spiny Norman said:

How is that done?

One way is to attach audio sensors at regular intervals, and listen for warning noises.

Video cameras all over the place would also seem to make sense, but I don’t know if anyone actually does that.

What about some sort of reflectors and laser measurement?

Yeah, that’s certainly done for inspections. I don’t know how much for continuous real time monitoring, but it would make sense.

sabotage

One way is to attach audio sensors at regular intervals, and listen for warning noises.

—

These can tell the difference from noise due to diurnal expansion and contraction?

Ian said:

One way is to attach audio sensors at regular intervals, and listen for warning noises.

—

These can tell the difference from noise due to diurnal expansion and contraction?

Easily.

Ian said:

One way is to attach audio sensors at regular intervals, and listen for warning noises.

—

These can tell the difference from noise due to diurnal expansion and contraction?

So they say.

I’ve never looked into it in detail.

Has anyone mentioned sonar yet? Insert a brief pulse of either sound or electricity into the steel and listen for reflections. This was used on the Genoa motorway bridge that collapsed, before it collapsed. There’s debate over whether the technology in use there was faulty or just old, it should have worked.

With an electrical pulse, it’s what power line engineers use to find the location of breaks in power lines after storms and fires.

The Rev Dodgson said:

sibeen said:

https://www.youtube.com/watch?v=e8PodEM4Y8g&ab_channel=BreakingPointsBreakingPointsVerified

An interesting video about a structural failure on a large bridge which crosses the Mississippi River. The defect was only picked up last month, luckily before it became catastrophic.

Bloody engineers!

“To the inspector who bypassed his boss, bypassed his client, and went directly to 911 to get the bridge shut down ASAP… your efforts to pass the Engineering Ethics course paid off, right there!”

Bloody engineers :)

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

Agree. Must have electronic monitoring.

Did you notice that this bridge has its crack through a welded steel box girder.

The Westgate Bridge that collapsed in Melbourne was also a welded steel box girder, and we don’t use them any more in Australia.

But the key point here is that the Westgate bridge did not fail because of fatigue, it had nothing to do with fatigue, nothing to do with cyclic loading due to traffic. The steel box girder of the Westgate Bridge failed because of resudual stresses. Welding doesn’t just introduce flaws into the structure from which cracks can grow. It also introduces warping stresses that are quite adequate to bring a steel bridge using welded box girders down without significant fatigue loading. Dimensional accuracy of the of the parts pre-assembly is crucial, and the displacement on this crack strongly suggests that errors in component dimensions and inadequate stress relief in the welds played a really big role here. With a crack caused solely by fatigue in a tension member, you do not get this amount of displacement.

In other words, it’s a pretty fair bet that the linked video totally misses the main cause of failure – residual stress in welded steel box girders. This is a major flaw in the use of welded box girders in bridge design.

One final comment. Residual stress can be induced by mechanisms other than welding and pre-assembly inaccuracy. One less likely but still plausible possibility on this bridge is the extra residual stress created by the earlier retrofit to enhance seismic stability.

mollwollfumble said:

The Rev Dodgson said:

sibeen said:

https://www.youtube.com/watch?v=e8PodEM4Y8g&ab_channel=BreakingPointsBreakingPointsVerified

An interesting video about a structural failure on a large bridge which crosses the Mississippi River. The defect was only picked up last month, luckily before it became catastrophic.

Bloody engineers!

“To the inspector who bypassed his boss, bypassed his client, and went directly to 911 to get the bridge shut down ASAP… your efforts to pass the Engineering Ethics course paid off, right there!”

Bloody engineers :)

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

Agree. Must have electronic monitoring.

Did you notice that this bridge has its crack through a welded steel box girder.

The Westgate Bridge that collapsed in Melbourne was also a welded steel box girder, and we don’t use them any more in Australia.

But the key point here is that the Westgate bridge did not fail because of fatigue, it had nothing to do with fatigue, nothing to do with cyclic loading due to traffic. The steel box girder of the Westgate Bridge failed because of resudual stresses. Welding doesn’t just introduce flaws into the structure from which cracks can grow. It also introduces warping stresses that are quite adequate to bring a steel bridge using welded box girders down without significant fatigue loading. Dimensional accuracy of the of the parts pre-assembly is crucial, and the displacement on this crack strongly suggests that errors in component dimensions and inadequate stress relief in the welds played a really big role here. With a crack caused solely by fatigue in a tension member, you do not get this amount of displacement.

In other words, it’s a pretty fair bet that the linked video totally misses the main cause of failure – residual stress in welded steel box girders. This is a major flaw in the use of welded box girders in bridge design.

One final comment. Residual stress can be induced by mechanisms other than welding and pre-assembly inaccuracy. One less likely but still plausible possibility on this bridge is the extra residual stress created by the earlier retrofit to enhance seismic stability.

(Just ignore me, I made at least a couple of mistakes in that I said above. But my main point still holds, be damn careful of steel box girders).

mollwollfumble said:

The Rev Dodgson said:

sibeen said:

https://www.youtube.com/watch?v=e8PodEM4Y8g&ab_channel=BreakingPointsBreakingPointsVerified

An interesting video about a structural failure on a large bridge which crosses the Mississippi River. The defect was only picked up last month, luckily before it became catastrophic.

Bloody engineers!

“To the inspector who bypassed his boss, bypassed his client, and went directly to 911 to get the bridge shut down ASAP… your efforts to pass the Engineering Ethics course paid off, right there!”

Bloody engineers :)

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

Agree. Must have electronic monitoring.

Did you notice that this bridge has its crack through a welded steel box girder.

The Westgate Bridge that collapsed in Melbourne was also a welded steel box girder, and we don’t use them any more in Australia.

But the key point here is that the Westgate bridge did not fail because of fatigue, it had nothing to do with fatigue, nothing to do with cyclic loading due to traffic. The steel box girder of the Westgate Bridge failed because of resudual stresses. Welding doesn’t just introduce flaws into the structure from which cracks can grow. It also introduces warping stresses that are quite adequate to bring a steel bridge using welded box girders down without significant fatigue loading. Dimensional accuracy of the of the parts pre-assembly is crucial, and the displacement on this crack strongly suggests that errors in component dimensions and inadequate stress relief in the welds played a really big role here. With a crack caused solely by fatigue in a tension member, you do not get this amount of displacement.

In other words, it’s a pretty fair bet that the linked video totally misses the main cause of failure – residual stress in welded steel box girders. This is a major flaw in the use of welded box girders in bridge design.

One final comment. Residual stress can be induced by mechanisms other than welding and pre-assembly inaccuracy. One less likely but still plausible possibility on this bridge is the extra residual stress created by the earlier retrofit to enhance seismic stability.

I don’t know that steel box girders are specifically not allowed in Australia.

Also the main problem with Westgate (and the other two big box girder collapses around the same time) was that the design procedures didn’t deal properly with shear lag and torsion and warping.

The Rev Dodgson said:

mollwollfumble said:

The Rev Dodgson said:

“To the inspector who bypassed his boss, bypassed his client, and went directly to 911 to get the bridge shut down ASAP… your efforts to pass the Engineering Ethics course paid off, right there!”

Bloody engineers :)

(but really a bridge that size these days should have electronic monitoring that would have picked it up as soon as it happened, rather than the next inspection).

Agree. Must have electronic monitoring.

Did you notice that this bridge has its crack through a welded steel box girder.

The Westgate Bridge that collapsed in Melbourne was also a welded steel box girder, and we don’t use them any more in Australia.

But the key point here is that the Westgate bridge did not fail because of fatigue, it had nothing to do with fatigue, nothing to do with cyclic loading due to traffic. The steel box girder of the Westgate Bridge failed because of resudual stresses. Welding doesn’t just introduce flaws into the structure from which cracks can grow. It also introduces warping stresses that are quite adequate to bring a steel bridge using welded box girders down without significant fatigue loading. Dimensional accuracy of the of the parts pre-assembly is crucial, and the displacement on this crack strongly suggests that errors in component dimensions and inadequate stress relief in the welds played a really big role here. With a crack caused solely by fatigue in a tension member, you do not get this amount of displacement.

In other words, it’s a pretty fair bet that the linked video totally misses the main cause of failure – residual stress in welded steel box girders. This is a major flaw in the use of welded box girders in bridge design.

One final comment. Residual stress can be induced by mechanisms other than welding and pre-assembly inaccuracy. One less likely but still plausible possibility on this bridge is the extra residual stress created by the earlier retrofit to enhance seismic stability.

I don’t know that steel box girders are specifically not allowed in Australia.

Also the main problem with Westgate (and the other two big box girder collapses around the same time) was that the design procedures didn’t deal properly with shear lag and torsion and warping.

Yes.

mollwollfumble said:

(Just ignore me, I made at least a couple of mistakes in that I said above. But my main point still holds, be damn careful of steel box girders).

No argument with that.

The Rev Dodgson said:

mollwollfumble said:

(Just ignore me, I made at least a couple of mistakes in that I said above. But my main point still holds, be damn careful of steel box girders).

No argument with that.

Watched the video all the way through now.

Thought he did a good job.

mollwollfumble said:

Has anyone mentioned sonar yet? Insert a brief pulse of either sound or electricity into the steel and listen for reflections. This was used on the Genoa motorway bridge that collapsed, before it collapsed. There’s debate over whether the technology in use there was faulty or just old, it should have worked.

With an electrical pulse, it’s what power line engineers use to find the location of breaks in power lines after storms and fires.

We don’t call that sonar :)

TDR – Time Domain Reflectrometry.

Witty Rejoinder said:

Peak Warming Man said:

They use drones to inspect them these days.

red light flashes in Creswick

Drone Picks Up Crack In Bridge.

Humans Fail To Notice.

:)

Tau.Neutrino said:

Witty Rejoinder said:

Peak Warming Man said:

They use drones to inspect them these days.

red light flashes in Creswick

Drone Picks Up Crack In Bridge.

Humans Fail To Notice.

:)

I watched the same video the other day, and it is interesting to see historical drone photographs showing the crack which suggests a failure to implement the inspection system rather than a failure of the system itself.

sibeen said:

mollwollfumble said:

Has anyone mentioned sonar yet? Insert a brief pulse of either sound or electricity into the steel and listen for reflections. This was used on the Genoa motorway bridge that collapsed, before it collapsed. There’s debate over whether the technology in use there was faulty or just old, it should have worked.

With an electrical pulse, it’s what power line engineers use to find the location of breaks in power lines after storms and fires.

We don’t call that sonar :)

TDR – Time Domain Reflectrometry.

Thank you :-) I couldn’t remember the phrase.

> Drone Picks Up Crack In Bridge. Humans Fail To Notice.

Yes! Big crack, too.