Bridge collapse

Hmmm per the article they were conducting a "stress test" on it. Seems kind of dumb to do without shutting down traffic.
 
Such a waste,doing a stress test without blocking off the area,not a smart move. May the victims Rest In Peace.
 
We do a fair number of load tests. Rule number 1 is “line of fire”. Keep your self out of the way of the obvious stuff failing. Thats 95% of effective safety planning in our shop, honestly.
 
There have been previous incidents of cable-stay bridges collapsing during construction. It's all a big puzzle and only after all the pieces are together it gains its full strength.
 
Old97 said:
We do a fair number of load tests. Rule number 1 is “line of fire”. Keep your self out of the way of the obvious stuff failing. Thats 95% of effective safety planning in our shop, honestly.
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CDOT learned a hard lesson on that one. There's way more than the engineers involved in a failure...even if they are protected by law.
 
Have you ever seen the video for the Tacoma Narrows bridge that was nick named galloping Gertie because of it’s oscillations when the wind blew above 25 or so mph? Here is the link showing its failure:

 
A Test?! Does not the definition of a Test include the possibility of Failing the Test? And preparing for such an outcome? Overconfidence/Arrogance much?
 
Briar Rabbit said:
Have you ever seen the video for the Tacoma Narrows bridge that was nick named galloping Gertie because of it’s oscillations when the wind blew above 25 or so mph? Here is the link showing its failure:

Click to expand...

I used to show that video to my son when he was in elementary school and making a lot of really careless errors in his math work. The point I was making is that careless errors and not being detail oriented and thorough can be very costly and potentially fatal. It took a while to convince him to be neat and to check his work carefully.

This video should be required viewing in all freshman introduction to engineering classes. Wouldn’t hurt to mention the Mars Climate Orbiter also in those classes.


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jimhorner said:
This video should be required viewing in all freshman introduction to engineering classes. Wouldn’t hurt to mention the Mars Climate Orbiter also in those classes.
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That was one epic screw up! One would think that NASA would have switched the SI units in the mid 80s/90s!
 
ARFlyer said:
That was one epic screw up! One would think that NASA would have switched the SI units in the mid 80s/90s!
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SI and English units seem to be a cultural thing. As an electrical engineer and an Analog IC designer, SI units were the norm. Measurements in the chip design world were all in SI units: microns, nanometers, milimeters. Then we would interface with the mechanical engineers who were responsible for the package design. Those guys worked in mils (thousandths of an inch). Very confusing. I would give them measurements in milimeters, and they would be talking mils. Not the same thing at all.

See? cultural. Electrical Engineering culture vs mechanical engineering culture. Very different!


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jimhorner said:
SI and English units seem to be a cultural thing. As an electrical engineer and an Analog IC designer, SI units were the norm. Measurements in the chip design world were all in SI units: microns, nanometers, milimeters. Then we would interface with the mechanical engineers who were responsible for the package design. Those guys worked in mils (thousandths of an inch). Very confusing. I would give them measurements in milimeters, and they would be talking mils. Not the same thing at all.

See? cultural. Electrical Engineering culture vs mechanical engineering culture. Very different!


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And after the mechanical engineers designed the package with nice 100 mil leg spacing, they give it to the sales people who sell it as 2.54mm pitch. And then the data sheet writers document it as 0.1”...
 
they were doing a failure test with cars driving underneath,,,,
and guess what???
the construction was NOT finished yet!
the design called for a center span support,,, not yet built!
 
robert lomax said:
they were doing a failure test with cars driving underneath,,,,
and guess what???
the construction was NOT finished yet!
the design called for a center span support,,, not yet built!
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Not only were cars driving underneath, there is a light on one side. From what I heard the cars that got crushed were standing at a red.
 
Old97 said:
We do a fair number of load tests. Rule number 1 is “line of fire”. Keep your self out of the way of the obvious stuff failing. Thats 95% of effective safety planning in our shop, honestly.
Click to expand...

Once upon a time in the old USSR, bridge load testing was performed with the design engineer and the construction supervisor (and their families, according to some accounts) standing under the bridge. I think that practice actually originated back in the Roman empire. Seems like an excellent way to motivate people to take responsibility for their work and to do it well.

Damn good idea. Perhaps we should adopt it.
 
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This will be the Hyatt Regency accident of our time, taught alongside Tufte’s assessment of the Columbia shuttle loss...

FWIW, I read elsewhere was that the “stress test” was an assessment of an installed strain measurement system. It didn’t sound like a load test - light loads should show that calculations match observations, but I’m no C.S.E.
 
scottfromboston said:
- light loads should show that calculations match observations, but I’m no C.S.E.
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In a linear region, yes. When the larger load introduces non-linearities and discontinuities, like non-elastic deformations and fractures that aren't reached by the light load, then no.

I'm an EE, not a CE, but it seems similar to small-signal versus large-signal responses in analog circuits. Large signals introduce saturations, hysteresis, recovery delay, thermal effects, etc., which aren't shown by small signals.

IIRC, the Hyatt Regency issue was that the original design required an impossibly long threaded rod, so during construction the design was changed to two separate rods. That effectively doubled the load on the bottom fastener of the upper rod.
 
Half Fast said:
Once upon a time in the old USSR, bridge load testing was performed with the design engineer and the construction supervisor (and their families, according to some accounts) standing under the bridge. I think that practiced actually originated back in the Roman empire. Seems like an excellent way to motivate people to take responsibility for their work and to do it well.

Damn good idea. Perhaps we should adopt it.
Click to expand...

I was in Poland when we had to pull over for a caravan of dump trucks. They pulled onto the bridge and the engineer measured the deflection in the middle then they drove off. Took about an hour for each bridge.
 
Briar Rabbit said:
Have you ever seen the video for the Tacoma Narrows bridge that was nick named galloping Gertie because of it’s oscillations when the wind blew above 25 or so mph? Here is the link showing its failure:

Click to expand...

jimhorner said:
I used to show that video to my son when he was in elementary school and making a lot of really careless errors in his math work. The point I was making is that careless errors and not being detail oriented and thorough can be very costly and potentially fatal. It took a while to convince him to be neat and to check his work carefully.

This video should be required viewing in all freshman introduction to engineering classes. Wouldn’t hurt to mention the Mars Climate Orbiter also in those classes.


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Click to expand...

That video was required viewing in my Freshman engineering class - in the fall of 1970. Now I live near there and have been over its replacement a few times. I prefer flying into TIW if I need to cross the narrows. :p
 
Engineers and calculations, ha. It’s not widely known but designers and builders totally blew it on load predictions while building an elevated section of I-70 in Glenwood Canyon. Neither the designers nor the builder had used a particular construction technique using precast concrete segments set in place by a purpose-built crane that used the elevated roadway it was building for support. They didn’t have enough compression preload on the roadway behind the crane so the roadway parted. Concrete really doesn’t do well in tension and they proved that point once again. Anyway, they spent a rough few hours getting structural scaffolding in place to save the crane and roadway. They then spent several months patching things back together. I was commuting through the canyon on weekends so I got to watch the progress, the near disaster, then the repairs.

As a side note, I are an injinear and I don’t trust engineers and their calculations. They prolly mean well but execution may well be lacking.
 
Not to say engineers don't make silly mistakes, because they do, but don't rush to blame the engineers until you know what the cost/time pressure put on them was. I've spent most of my adult life (and some before adulthood) writing software. I can write perfect software. But it takes a (relatively) long time and costs a lot more than I've usually been allotted.
 
jsstevens said:
Not to say engineers don't make silly mistakes, because they do, but don't rush to blame the engineers until you know what the cost/time pressure put on them was. I've spent most of my adult life (and some before adulthood) writing software. I can write perfect software. But it takes a (relatively) long time and costs a lot more than I've usually been allotted.
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Did you just write that you can do it perfect but people don’t let you? Wow. I’m in the camp that says one can strive to be perfect but the nature of the human condition is that we aren’t perfect and never will be.
 
jimhorner said:
The point I was making is that careless errors and not being detail oriented and thorough can be very costly and potentially fatal. It took a while to convince him to be neat and to check his work carefully.
Click to expand...

Don't forget the bad optics on the original Hubble Space Telescope....

-Skip
 
Clark1961 said:
Did you just write that you can do it perfect but people don’t let you? Wow. I’m in the camp that says one can strive to be perfect but the nature of the human condition is that we aren’t perfect and never will be.
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Within a limited scope of a particular software solution, yes. Its a quite limited scope. Maybe it's more accurate to say I can write functionally flawless software within a particular scope. But the extra analysis of failure modes and testing are usually not something people are willing to pay for. And the extra space taken up by code paths that may never get taken. And frankly, in non-life threatening cases (say a game on your phone) they're right. It's not worth it. Just restart the thing and drive on.

And, yes, I've made my share of silly mistakes and assumptions in my career as well. But a significant part of engineering as a career involves making trade offs between cost, schedule and quality. And most engineers do not get the final say, they can only recommend courses of action.

As for otherwise perfect, no way in heck. Just ask my wife. :D
John
 
Skip Miller said:
Don't forget the bad optics on the original Hubble Space Telescope....

-Skip
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Boon for some, though. Pieces I had build and held in my hands are on board Hubble, went up as part of SM1.
 
Quite a few of us on this board are engineers. Any of you guys wear an iron ring / engineer's ring? Do you know the story behind it?

This bridge collapse immediately brought the ring story to mind.
 
Half Fast said:
Quite a few of us on this board are engineers. Any of you guys wear an iron ring / engineer's ring? Do you know the story behind it?

This bridge collapse immediately brought the ring story to mind.
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My school held the ceremony separate from each graduation. It seemed like mostly foreign students (read Canadians) participated. As it turned out I did a lot of design/construction/repair right after graduation so it would have been appropriate. Later I sat at a desk analyzing a lot of data which wasn’t exactly working/building for the benefit of society.
 
Half Fast said:
Quite a few of us on this board are engineers. Any of you guys wear an iron ring / engineer's ring? Do you know the story behind it?

This bridge collapse immediately brought the ring story to mind.
Click to expand...

Never heard of it until now.
 
jimhorner said:
SI and English units seem to be a cultural thing. As an electrical engineer and an Analog IC designer, SI units were the norm. Measurements in the chip design world were all in SI units: microns, nanometers, milimeters. Then we would interface with the mechanical engineers who were responsible for the package design. Those guys worked in mils (thousandths of an inch). Very confusing. I would give them measurements in milimeters, and they would be talking mils. Not the same thing at all.

See? cultural. Electrical Engineering culture vs mechanical engineering culture. Very different!


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I think only IC guys operate in metric. PCB layouts are in mils, SMD dimensions in English (ex., 0805).
 
Half Fast said:
Seems like an excellent way to motivate people to take responsibility for their work and to do it well.

Damn good idea. Perhaps we should adopt it.
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that would be great if it was extended to law enforcers, bureaucrats, political leaders and law makers, who are generally unaccountable for their failures.
 
paflyer said:
I think only IC guys operate in metric. PCB layouts are in mils, SMD dimensions in English (ex., 0805).
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Yeah, and I’m an old enough curmudgeon to grumble about it and say that everyone should have switched over to the SI system years ago. So much simpler. Everything is a factor of 10.

I mean really, slugs, pounds feet, pounds mass, teaspoons, tablespoons, cups, quarts, gallons, 12 inchs per foot based off of some old king’s foot length, 3 feet per yard, 5280 feet per mile, acres, drams, ounces of volume, ounces of weight, horsepower (horsepower? really? how does that make sense when most people have no real world experience with an actual horse!) ,etc. It’s crazy!

SI is simple and straightforward.

And besides, most, if not all, of the English units are now defined based on the SI standards. For example, the inch is defined as exactly 2.54 cm. Centimeters define the inch, not the other way around. We should have done more to switch this country over to the SI system years ago.

Dang kids, get off’n mah yard!

Grumble.


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Sac Arrow said:
Never heard of it until now.
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I wish it were more common in the US; it seems to be ubiquitous in Canada. Many of us design things (aircraft, bridges, spaceships, medical equipment, etc.) for which human lives hang in the balance, and I think sometimes we might not be as diligent as we should be or take the responsibility seriously enough. The ring can be a good and constant reminder.
 
jimhorner said:
Yeah, and I’m an old enough curmudgeon to grumble about it and say that everyone should have switched over to the SI system years ago. So much simpler. Everything is a factor of 10.

I mean really, slugs, pounds feet, pounds mass, teaspoons, tablespoons, cups, quarts, gallons, 12 inchs per foot based off of some old king’s foot length, 3 feet per yard, 5280 feet per mile, acres, drams, ounces of volume, ounces of weight, horsepower (horsepower? really? how does that make sense when most people have no real world experience with an actual horse!) ,etc. It’s crazy!

SI is simple and straightforward.

And besides, most, if not all, of the English units are now defined based on the SI standards. For example, the inch is defined as exactly 2.54 cm. Centimeters define the inch, not the other way around. We should have done more to switch this country over to the SI system years ago.

Dang kids, get off’n mah yard!

Grumble.


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Well, it's not as if SI doesn't have it's arbitrary bases. The kilogram is based off a chunk of platinum in France, not exactly ground-breaking. Defining a meter as related to how far light travels in a second. Is that relevant to how some guy builds houses? Not really. There are some reasons to support both imperial and metric systems, it's not as if SI doesn't have it's pros/cons. The largest benefit obviously being conversion simplicity.
 
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