Bridges, engineers and technology
There have been many programs on TV about the history of bridge engineering. Before the advent of modern science, bridges were massive.
Wartime films show waves of bombers trying to drop ancient bridges. Direct hits had minor effects. Gigantic bombs had to be developed to create earthquake effects to drop some of them.
Modern bridges are designed so that every grain of steel is stressed to it's maximum. A single bolt, weakened by a few molecules of rust, threatens the entire structure.
Wartime films show waves of bombers trying to drop ancient bridges. Direct hits had minor effects. Gigantic bombs had to be developed to create earthquake effects to drop some of them.
Modern bridges are designed so that every grain of steel is stressed to it's maximum. A single bolt, weakened by a few molecules of rust, threatens the entire structure.
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Well...so much for that.
No more modern bridges for me.
Doug0 -
I don't think so. I worked on bridges in my youth, and they were so over engineered that the usual 400% over build was exceeded. 0 -
Not true:
Bridges are very well engineered and made. MAINTENANCE on them suffers because out government spends too much money on feel good social programs and too little on infrastructure.
Corrosion will most likely be the cause of the failure. The Government KNEW the bridge was junk and needed replaced. They white washed it so they could spend the money marry fags, give free condoms and abortions out to one and all instead of fixing the bridge.0 -
I can't help but be a little disgusted watching the "first responders" pat each other on the backs and tell us what a great job they did in the rescue efforts.
"We did the job that we're paid so well for. You're so lucky to have us!"
The story I heard on the news last night mentioned that many of the survivors were rescued by citizen bystanders.
El Presidente, in his press conference, had about 2 sentences regarding the collapse, then turned it into a political speech about the evil democrats and their refusal to send him a spending bill.
What a MORON!!!
Prayers to the victims and their families.0 -
Well the federal gov has come to the rescue today. That makes me feel so much better. 0 -
Buy a beautiful new car. Never change the oil,inflate the tires, align the front end, or clean the bugs off the windshield. Then 5 years later, complain they don't build them like they used to. Modern bridges are well designed, well constructed, and poorly maintained. If you saw the underside of half the bridges you drive over- you wouldn't. 0 -
Things such as bridges are designed with a failure factor built into them. I believe the usual factor is around 10 times. 0 -
quote:Originally posted by Dennis Smith
There have been many programs on TV about the history of bridge engineering. Before the advent of modern science, bridges were massive.
Wartime films show waves of bombers trying to drop ancient bridges. Direct hits had minor effects. Gigantic bombs had to be developed to create earthquake effects to drop some of them.
Modern bridges are designed so that every grain of steel is stressed to it's maximum. A single bolt, weakened by a few molecules of rust, threatens the entire structure.
Older is better? Uh huh. How about the Angers Bridge, a suspension bridge which collapsed in 1850 due the the resonance of approx 400 troops marching across is in close formation? Failure analysis is a very specific engineering specialty and while it is not my field, all structural engineers study engineering and design disaster/failures. While there have been calamities directly tied to poor designs, most often lack of attention to normal maintenance or the postponing of even basic repairs is the cause of structural failures. The bridge in question uses a tried and true design which has been proven suitable for use on highway bridges or viaducts for many decades. This design has a number of redundant safety features built into it and should have been capable of dealing with even the highest torsional stresses, even when combined with high shear stress. Exactly why the span fell is still unknown but a lack of maintenance to the hanger plates and-or hanger pins could easily be the root cause.0 -
When you think of how old the bridges are that we have now, and what they were designed for at the time they were built. Now think of the new bridges that were bulit my the lowest bidder.Now add in the crooked politicians and the fat cat contractors.Just to make it interesting add inspectors that were politicly apointed. Don't that make you feel all warm and fuzzy inside? 0 -
Me thinks the Northerner's used too much road salt on them.. 0 -
try it yourself
http://bridgecontest.usma.edu/0 -
A bridge is only as strong as it's weakest link. Just ask us here in earthquake country[;)] 
CA 1989, there are cars with folks in them between both decks. They were crushed about 6" flat in spots.0 -
This was a "modern bridge" when it was built 60 odd years ago.
I'm sure they'll be laughing at us and our "engineering prowess" in another 60 years.
The announcer says the bridge is high above the river below, but it's not a river at all. Most people will recognize it as the Tacoma Narrows, a narrow passage on Puget Sound.
http://www.youtube.com/watch?v=HxTZ446tbzE&mode=related&search=0 -
quote:Originally posted by bpost1958
Not true:
Bridges are very well engineered and made. MAINTENANCE on them suffers because out government spends too much money on feel good social programs and too little on infrastructure.
Corrosion will most likely be the cause of the failure. The Government KNEW the bridge was junk and needed replaced. They white washed it so they could spend the money marry fags, give free condoms and abortions out to one and all instead of fixing the bridge.
Nancy Pelosi would say money was wasted on Iraqi reconstruction when it should have been spent on road maintenance. More money is needed to fight this problem. Higher taxes is the only recourse.0 -
It's interesting that video shows a complete section just dropping almost level. Both sides dropped at the same time, almost as if it was engineered or planned.
Yes, I'm saying conspiracy theories are in the brewing.0 -
quote:Originally posted by Captplaid
It's interesting that video shows a complete section just dropping almost level. Both sides dropped at the same time, almost as if it was engineered or planned.
Yes, I'm saying conspiracy theories are in the brewing.
From that video, its hard to determine what section of the bridge that is in the video. This bridge was 1900 feet long, that section was much less then that.
Just because something falls straight down doesn't mean that it was done planned.0 -
quote:Originally posted by shoff14
quote:Originally posted by Captplaid
It's interesting that video shows a complete section just dropping almost level. Both sides dropped at the same time, almost as if it was engineered or planned.
Yes, I'm saying conspiracy theories are in the brewing.
From that video, its hard to determine what section of the bridge that is in the video. This bridge was 1900 feet long, that section was much less then that.
9-11 conspiracy theory logic[;)]
Just because something falls straight down doesn't mean that it was done planned.0 -
That's my hometown. I know people who traveled that bridge within an hour of its collapse.
It fell down. No conspiracy is necessary. We may need to rethink our evaluation and maintenance of our infrastructure but this looks to me very much like a crappy accident. Maybe we can learn how to prevent such accidents in the future.
that is all.0 -
The thing that just slays me is that the announcers are all parroting : "the bridge was marked DEFICIENT", and "it had Cracks", and they say things like "How could we, in this modern day and time, have bridges with cracks?"
These "journalists" are just injecting their ignorance and herding the sheeple. Every structure, save some medical ones and some of the ones we send into Space, have cracks in them , AB INITIO.
The unscientific, innumerate, comfortably numb, poorly educated masses come out of their contented torpor only when whipped to a mob-frenzy, by the "Journalists" - who know nothing more than the average masses!! Senators spout platitudes: "Bridges shouldn't just fall down".
EVERYTHING made by man eventually succumbs to Gravity or Entropy. Every time you load any structure, even within elastic limits, somewhere, a crack grows a little, or crystals change their arrangement. Fatigue grows. Then, wings fall off, or bridges fall down. It is the way of things. Inspection and Maintenance can stay the demise a while, but eventually....
Good maintenance and good record-keeping would have probably averted this disaster. Too bad Politics and Money concerns probably caused
this to come about.
To the "conspiracy minded": View the footage again - if you are observant, you can see that the near side of the water span failed first - it fell a few feet before the beams and joints of the far side crippled and failed. Nothing happened "Simultaneously".0 -
All this tripe about politics should never even be considered; wasteful management of the Federal Highway Funds intended to repair, replace and inspect the Nations' bridges, dams, R/R crossings and culverts is the sole source of blame in this case.
Unless they were using vibratory steel wheel rollers on the Eastbound lanes during the resurfacing.
Corrosion (and quite probably, vibration), not corruption was the culprit.
BTW, didja see that Gov/Prez Richardson called for more extensive inspection on nM's bridges? The Bridge Inspection Crews have been laid off to save money for his campaign. Kinda like curing a cough by decapitating the patient.0 -
R: conspiracy theory- when doing demo of a bridge for purposes of DAMAGE (not removal) you do not drop the whole span at once- you drop one section, and let the leverage of that section pull/twist/shatter other members. MUCH more damaging. As kristov said, much too early- but my money is riding on falure of pins/hangers, or diapraghm failure (cross bracing between deck girders, keeps them vertical and paralell.) one spectacular failure few years back caused by plugging surface drains with asphalt when repaving. snow melt w/salt ran thu expansion joints, corroded the hangers/pins. major cable stayed bridge here in VA has just had weight limit lowered- new bridge, corrosion to cables. Repairs under way now. 0 -
I think everyone should just drive spaceships. Then we won't need bridges. 0 -
If they're made by mankind, they'll fall out of the sky. [8D] 0 -
I have taken extensive classes on bridge inspection and have inspected many bridges over the years. The federal government has a standard format in which all states need to report their inspections on a regular basis. Bridge inspections for all bridges are happening all the time.
Obiviously though, not all bridges are scheduled to be inspected on the same intervals. Newer bridges in our state are on a 4 year inspection schedule. They are looked at once every 4 years. It goes down from there based on condition ratings. Most are bi-annual, some are annual and some are so bad, they receive monthly inspections.
They are automatically sorted in a computer based on inspection ratings, and the ones at the top (worst condition) are the first ones to be put in the program the following year.
Many bridges in Illinois were made in the 60s and are fine. The vast majority of bridges are not fracture critical. Meaning, most bridges can have a support go bad, a bearing fail or a beam or two fail and the bridge will not fall down. The fracture critical bridges are the real danger, and I don't know why states keep engineering them. The bridge in Minneapolis did not appear to be one of these and I really have no idea why or how it could have failed like that.
Modern bridges, even from the 60s, are over-built. There is no way they should be able to fall down like that. Weight could not have been a factor in the disaster. Besides that, it was only at half capacity.
I'm not an engineer and do not claim to be an expert. The reality comes down to that there are a lot of bridges. Not many inspectors. Even when they are there, there are vast areas to 'look' over. There is only so much that can be done on most inspections, even going over every bridge with a fine toothed comb. And then, it's likely nobody will be back to look at it for at least another year or two unless major problems were noted.
It will be interesting to see what the investigation uncovers up there.0 -
quote:Originally posted by Flying Clay Disk
quote:Originally posted by Dennis Smith
There have been many programs on TV about the history of bridge engineering. Before the advent of modern science, bridges were massive.
Wartime films show waves of bombers trying to drop ancient bridges. Direct hits had minor effects. Gigantic bombs had to be developed to create earthquake effects to drop some of them.
Modern bridges are designed so that every grain of steel is stressed to it's maximum. A single bolt, weakened by a few molecules of rust, threatens the entire structure.
Clearly we have a Senior Civil / Structural Engineer here.
Turn off the discovery channel!
For his sake I hope not unless he enjoys being called an idiot, a moron, accused of talking out of his a$$, and a whole host of other insults that have come my way.0 -
quote:Originally posted by Flying Clay Disk
Clearly we have a Senior Civil / Structural Engineer here...not to mention a WWII bombardier, weapons expert and geophysicist.
Turn off the discovery channel!
Yep, I came to the right place. Thanks for all the replys. I've learned at lot.
Did some research on pins and hangars (had never heard of them before) Learned that if they rust and "lock" in place, they will break.
So, my statement about modern bridges was pretty ignorant, but still "slightly" true. The failure of the smallest component can cause the entire bridge to collapse.
The more i learn the more i realize how little i know [:D]0 -
You did research on things like hangers and pins? What a total waste of time! The next thing you know you'll be telling us how you want to go back to school, become a smart a$$ed college boy, or even worse; actually become an engineer! Forget all about that nonsense and either get yourself a real job (union of course) in a widget factory or go out and join the military. These are your only true opitions if you wish to escape ridicule from Gun Broker members who consider professional degrees to be a total waste of time and the people who hold then to be dead weight in our society. I hold engineering degrees in three fields: Petroleum, structural, and structural design and if I broke this bridge collapse down step by step covering every aspect of the both the design and construction of the bridge all the way through to it's failure some GB member from Des Moines who is a hog farmer would chime in, tell me I don't know a thing about the subject and then call be an idiot! 0 -
Fortunately the pin and hangar design is long obsolete. Most people have probably never even been on one. That is a fracture critical design.
Here is the infamous pin and hangar bridge that got the ball rolling on modern bridge inspections in this country:
http://filebox.vt.edu/users/aschaeff/silver/silver.html
They did find the cracked eye bar that made the whole thing give way. If you read at the end though, even modern inspections on that structure would not have been able to recognize the impending failure without taking the bridge apart and performing testing.
IMO, all of those bridges should be replaced asap, whatever the cost.0 -
Wow, you were right on time with that link, vess1. I saw that bridge on TV last night. I never saw one where the truss work was connected to the suspension lines (chains?). I meant to look it up today, but my few remaining brain cells had already deleted it.
Oops, gots to edit: There must also be some confusion in terminology. There are more modern pin and hanger designs than the old eye-bars. Here's a schematic:0
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