strapping bridges

[WA1GFZ]

How did the Romans build bridges that lasted the test of time.
They didn't use iron they used stone under comression.
We may make some pretty structures these days but they don't last.
Imagine the Golden gate made from store quite a job but it would last.
Let's see the RT 35 bridge another one I've been on that has come down.
Oakland Bay bridge
Bridge in Ct that dropped a section
Bridge over the 405 in LA.

I think we need to find a different construction material and stop building short term art that doesn't last.
Like building a QRO rig with a broadcast variable as a loading cap.

[Bill, KD0HG]

Most of those bridges were prolly soaked in de-icing salt for several months every year. For decades.

Use stainless steel..

How did the Romans do it? Bring back slavery- Makes it easy to build affordable stone monuments.

[KF1Z]

Stop paying overpriced engineers to design products that are "cost-effective"....

end of problem.......

[WA1GFZ]

I think is was in first or second grade when they started building bridges held up by a hinge pin. At that young age I could see it was a stupid idea as we learned years later when the section fell.
The Army corp. of Engineers could do a better job compared to these idiots trying to build art that doesn't last.

[KF1Z]

Most of those bridges were prolly soaked in de-icing salt for several months every year. For decades.

Use stainless steel..

How did the Romans do it? Bring back slavery- Makes it easy to build affordable stone monuments.

I'm not sure stainless steel would work.   I thought high concentrations of salt in the presence of flexing would cause local pitting of stainless steel, causing local areas of corrosion that would grow.   Any metalurgists out there?

You are correct.....
It's called Stress Corrosion Cracking....

Chlorides (salt water). react with (eats) the chromium oxide layer....

Lots of stuff eats stain"less" steel....
It's just a bit more RESISTANT to rusting/corrosion than plain old steel,

(The high chromium content of stainless  reacts with oxygen to form a layer of chromium oxide, that keeps water and air away from the steel)


===========

Use rocks.... they've been around a few years.... and I expect they'll be around a bit longer...

[kf6pqt]

I'm no engineer, but I think the Oakland Bay bridge held up pretty good considering the heavy torqueing it got at the hands of that bigass earthquake!

Also on that list is the overpass before the bay bridge that came down, er melted, when that gasoline truck tipped and blew up underneath it earlier this year.

Speaking of gasoline, how much of the gas tax money really goes to the roads vs politicians pet projects?

At the risk of getting the thread locked, I say we should stop subsidizing welfare babies, and make the illegal immigrants pay income tax... then we could probably pave all of our new (overbuilt) bridges with gold bricks!

[WU2D]

My childhood friend Dave Powelson went to Clarkson when I was at RIT and he graduated with a Civil E. He eventually ended up as the dude who runs the NH Bridge inspectors who grade bridges. He was on TV this morning.

Back in the late-1980's when he was first working as an inspector, he said that we were in bad shape and that many bridges were in trouble, but much of the money goes towards road repair to promote tourism and only the absolute worst ever get attention.

Dave is a good honest person as I am sure most inspectors are but the problems are vast.

http://www.nhpr.org/node/6114

Mike WU2D

[WBear2GCR]

The answer to this issue is fairly simple.

Bridges and roads have a known usable life.
After that they must be replaced or repaired in a significant way.

During their usable life they need to be maintained and inspected on a really high cycle basis. I think the GW Bridge, for example, is in essence continuously painted, they start on one side, and within a year or so, they go back and do it again. As I understand it.

Beyond that Core10 steel seems to work well compared to painted steel.

You should see the RAILROAD bridges around here. Afaik and can see they have NEVER EVER had a coating of paint, nor do they seem to get any maintenance that I can see. Good thing that when they were built steel was cheap and good, and they were put together using riveted construction. Why they are still there spanning the Hudson River or over roadways seems quite miraculous to my eyes.

Those who appear to have the most control over $$ seem to be most interested in profits to be had anywhere, not wealth for this nation. Infrastructure that works = wealth, not profit. What they DO with or need with all that "profit" is beyond my limited and weak understanding.

                _-_-WBear2GCR

[WA1GFZ]

We have a stone bridge in Hartford that goes over the river. I've seen water almost up to the deck and it never moved. Stone under compression....just like god built the crust

Take the profit out and put quality back in.

[WA1QHQ]

If you think road bridges are bad the real dirty little secret is railroad bridges. A very large percentage of railroad bridges are in dangerous ready to colapse condition and the railroads being almost always broke do not have the funds for inspection or repair. Many of these railroad maintained bridges also have road traffic pass over or under the them.

Mark WA1QHQ

[W9GT]

Bridge in Ct that dropped a section

Wasn't that a section in one of the bridges on I95 between NYC and Stamford, CT that fell down a few years ago?  I had driven over that span many, many times when I was working in Stamford for GTE and made the trip between LaGuardia and Stamford many times.  Scary to think that I could have made a very rapid and unscheduled vertical trip down to ground level at that location!!!  I think there were fatalities in that collapse as well...don't recall.

73,  Jack, W9GT

[W3RSW]

Well, the Romans had lots of arches, small spacing between each a/c load limits of stone, layers of arches upon arches when required for elevation, e.g., the tri-level viaducts.  Modern road systems continually try to span ever larger 'ditches' for many reasons.  Hell, in France right now they're spanning a complete broad valley approaching the distance between NYS finger lakes, just for the sake of saving five minutes. 

I-35 was a single arch and high becaue of river traffic requirements under it.  It also had harmonic "load" stressing never endured by stone viaducts or temples.  Most of the ancient world constuction is now in ruins because of earthquakes or pirating by later "civilizations," St. Peter's
Basilica or most of the older city of Alexandria next to the pyramids now missing a 'cubic mile' of the whitest limestone being a couple of good examples.  - Yeah, the "Best quarries in the world," brought to you by the ancients....  recycled by the newly annointed."

Yes, stress corrosion cracking, hydrogen embritlement, etc. are very serious problems in most any metallurgical construction be it pipelines, bridges, or skyscraper skeletons.  Much research has been devoted to eliminating chaotic failure of such.  Given the hundred thousand bridges in this country made from wood to self-oxidizing steel the record is remarkably clean. 
Statistically you're going to have failures, even with six sigma QC programs sooner or later something will fail. - Absolutely guarenteed, numerically speaking.  So how many have had a tire blow lately?   How many pileups with death tolls approaching or exceeding bridge failures result from primary or secondary causes of tire failure, brake failure, you name it? 

Yeah, none of us want to be crossing a bridge at "collapse time" but then how many of us want to twist and wind our way down a canyon, cross a tiny bridge and wend our way back up at 10mph.. or ford a creek, or wait for a train to cross I-70, or wait for your brother's sailboat to clear the old creaky drawbridge ...ad infinitum. 

Bear's right. If you must design the highest, latest and greatest using the hottest 'new' technology, then for minimum disruption plan a replacement or major repair cycle. Fund it upfront,  (yeah right, given the victim nation, entiltlement mentality egged on by complete parties of oppositon driving our illustrious politicians and litigators these days.)   Well ok, at least sell bonds or whatever including funding stream for later major repairs before construction. 

Certainly not lastly, bridges like anything else are cost based on safety factors, materials, technology of combining the same, anticipated loads, usage, and ... right, an expected life. 
Mean time before failure is not just an aeronautical throwaway term.

Regardless, heads will roll, scapegoats will be found...  and reams of very costly paper will be expended pointing fingers, suing everybody left alive or in anyway deemed partially responsible. 

[W1RKW]

Yes Jack, That was the Mianus River bridge in Greenwich on I-95.

A buddy of mine and I drove over that bridge about 40 minutes before it dropped coming back from CBGB's in NYC that evening (morning).   When we found out about it the next morning our jaws dropped.  And you are correct. Three or 4 people lost their lives in that collapse.

Bridge in Ct that dropped a section

Wasn't that a section in one of the bridges on I95 between NYC and Stamford, CT that fell down a few years ago?  I had driven over that span many, many times when I was working in Stamford for GTE and made the trip between LaGuardia and Stamford many times.  Scary to think that I could have made a very rapid and unscheduled vertical trip down to ground level at that location!!!  I think there were fatalities in that collapse as well...don't recall.

73,  Jack, W9GT

[W1RKW]

Frank,
There are several bridges on the good ole Merrit Pkwy that are built out of stone.  I'd be willing to bet that they will stand the test of time compared to the new and improved steel bridges. 

There's a stone bridge in Old Lyme which is an I-95 over pass for Rte 1.  That is stone as well.  It's a cool looking bridge.  I bet it will last many lifetimes as well.

How did the Romans build bridges that lasted the test of time.
They didn't use iron they used stone under comression.
We may make some pretty structures these days but they don't last.
Imagine the Golden gate made from store quite a job but it would last.
Let's see the RT 35 bridge another one I've been on that has come down.
Oakland Bay bridge
Bridge in Ct that dropped a section
Bridge over the 405 in LA.

I think we need to find a different construction material and stop building short term art that doesn't last.
Like building a QRO rig with a broadcast variable as a loading cap.

[k4kyv]

I-35 was a single arch and high becaue of river traffic requirements under it. 

But the 10th Avenue bridge right next to it has a pier in the middle of the river.  River traffic would already have to dodge that pier, so a second pier would not have  made navigation any more difficult.

View diagram of bridge collapse

[k4kyv]

Most of those bridges were prolly soaked in de-icing salt for several months every year. For decades.

Use stainless steel..

Stainless steel will also rust.  And it is not as strong as regular steel.   I have seen warnings that stainless steel hardware used in tower work is more prone to failure than regular steel. Combining chromium with steel weakens the latter. IIRC the inoxydable characteristic of stainless works kind of like the characteristic that prevents aluminium from taking solder - the chromium content in the alloy reacts with the air to form a thin skin that protects it from further oxidation.  For example, I have seen rusty spots inside so-called stainless steel dishwashers.  My stainless steel kitchen sink sprang a leak after years of use and I had to replace it.  My present one has some deep pits in the metal that will likely start leaking in the near future.

Aren't there other, less corrosive de-icing agents than salt?  They might be more expensive,  but certainly a lot cheaper than periodically replacing bridges.

[W1RKW]

When I built the deck for the house, I used stainless steel screws for the decking.  I found they were definitely weaker than your standard coated steel decking screw.  They were more prone to torsional twist when screwing them down. Also they were more expensive than their less expensive plain jane coated hardened steel counter part.

Most of those bridges were prolly soaked in de-icing salt for several months every year. For decades.

Use stainless steel..

Stainless steel will also rust.  And it is not as strong as regular steel.  I have seen warnings that stainless steel hardware used in tower work is more prone to failure than regular steel. IIRC the inoxydable characteristic of stainless works kind of like the characteristic that prevents aluminium from taking solder - the chromium content in the alloy reacts with the air to form a thin skin that protects it from further oxidation.  For example, I have seen rusty spots inside so-called stainless steel dishwashers.  Combine chromium with steel weakens the latter.

Aren't there other, less corrosive de-icing agents than salt?  They might be more expensive,  but certainly a lot cheaper than periodically replacing bridges.

[Bill, KD0HG]

Didn't know all of that about stainless..I had always assumed that it was pretty much chemically inert material. My left arm bones were reconstructed with stainless steel some time ago, now I'm wondering about the long-term structural strength of the repair- LOL.
Maybe titanium would have been better?

Anyone know why stainless steel is non-magnetic?

[W9GT]

Yes Jack, That was the Mianus River bridge in Greenwich on I-95.

A buddy of mine and I drove over that bridge about 40 minutes before it dropped coming back from CBGB's in NYC that evening (morning).   When we found out about it the next morning our jaws dropped.  And you are correct. Three or 4 people lost their lives in that collapse.

Bridge in Ct that dropped a section

Wasn't that a section in one of the bridges on I95 between NYC and Stamford, CT that fell down a few years ago?  I had driven over that span many, many times when I was working in Stamford for GTE and made the trip between LaGuardia and Stamford many times.  Scary to think that I could have made a very rapid and unscheduled vertical trip down to ground level at that location!!!  I think there were fatalities in that collapse as well...don't recall.

73,  Jack, W9GT

Thanks for the memory jog Bob.  Sure glad that you made it across safely!  That was a scary thing to find out about.  More scary if you were as close as you fellows were!!

73,  Jack, W9GT

[KB2WIG]

              "  Anyone know why stainless steel is non-magnetic? "

Some ss is magnetic, there is a name for the stuff that isn't and I dont know it...The addition of nickel into steel changes the structure and and this cuts down/eliminates the magnetism.....   can't find my chem books.....   klc

found this            http://www.physlink.com/Education/AskExperts/ae546.cfm

[k4kyv]

You need to use the weaker but more expensive stainless decking screws because the formula for pressure treated lumber was modified "for the children".  The older formula was slightly more toxic, and the primary concern was about it being used to build wooden playground equipment, so the wood preservative used in all treated lumber was reformulated.  The new stuff contains far more copper and is highly corrosive, especially when in contact with zinc galvanising.  As with all copper products these days, it is also substantially more expensive than the older stuff.

It would have been too much like common sense to make a special grade of lumber with reformulated preservative for playground equipment and other uses where people would frequently come in direct contact with the wood, but keep the older variety in production for framing and other uses where the wood remains inaccessible to direct contact.

You have to be very careful with stainless decking screws, not to twist them in two if you use a power screwdriver.

[Bacon, WA3WDR]

18-8 stainless steel, a very common type for hardware, is significantly magnetic.  Not as much as regular steel, but significantly nonetheless.

316 stainless steel, a better quality type, is less magnetic than the 18-8 type.  But if you stick a strong magnet into a box of 316 hardware, you will still see it stick to the magnet.

There are a large number of standard types of stainless steel.  There are varieties of the 300, there is a 400 series, and there is 17-7, which I guess is lower quality than 18-8, but I'm not sure.  It all qualifies as stainless steel, but there are major differences in corrosion resistance and magnetic characteristics and probably strength.

There are a boatload of varieties of other materials like aluminum and copper as well.  It can be downright confusing when you suddenly get a selection and you were just thinking of aluminum or copper or stainless steel, etc.  What we usually think of as 'aluminum' is really an alloy that has decent stiffness, yet decent bendability, so it can be formed into shapes, and then it can hold them.  I've seen 'aluminum' that was so soft that it seemed like lead.  And usually the 'aluminum' has been surface treated by anodization or alodyning, so that it does not corrode when you touch it, etc.

There is pure copper, which is a pretty good conductor of heat, and there are alloys that look about the same, but they are not half as good at conducting heat.  It's more than the oxygen content; there are other metals mixed in.

[AF9J]

Just some thoughts - I had stress analysis for basic engineering classes I had to take, but I'm no civil engineer.  The only possibly "less corrosive" mixture that is used instead of salt in the winter time, is a calcuim chloride solution.  It's been tried around here, but it's more expensive then regular salt, and sometimes plugs up the spreaders because it's sort of in a semi-slurried form.  Remember trussed bridges are made to work under compression loads, not tension loads.  Start adding tension from vibrational movement (say from traffic, or the wind), twisting, etc. and they will fail sooner or later, due to metal fatigue.

Bridges that fell - some of you may remember me mentioning in another thread, the Hoan Bridge in my neck of the woods, that decided to start dropping chunks from it a few years ago.  Luckily nobody got hurt when it happened, but at the cost of several million dollars worth of repairs (they found stress cracks in the bridge), it was out of commission for about a year.  The stupid thing was barely 30 years old!

I read somewhere years ago, that our infrastructure is falling apart.  Nobody wants to spend the money to maintain it.  In the case of roads, what do they do to save time and money? - they slap on another layer of asphalt.  In 3 or 4 years time, it's usually starting to get ratty again.  I don't even know if tolls would do the trick for road or bridge maintenance funding.  I live about 85-90 miles from Chicago.  Once in a great while, I've had to go down to the north Chicago 'burbs.  I can usually tell when I hit I-294, the Tri-State Tollway.  The road surface is awful.  I've seen county highways in better shape.  The sides of the overpasses and bridges also look bad (you can occasionally see rebar in sections where the concrete has broken away).  You wouldn't expect this kind of stuff on a tollway that rakes in money by the ton (traffic is usually very heavy on the Tri-State Tollway), but it sure seems to be the case there.  Like Bear said, there has to be a desire to do decent (not slap a bandaid on it) maintenance on the infrastructure to keep it in good shape.  A lot of states don't want to do anything, until it starts to get out of control.  Case in point - the Marquette Interchange in Milwaukee.  It should have been replaced in the early 90s, especially since it was getting old and worn out, and had been designed for 50s era traffic patterns.  But noooo, it took tons of gridlock, and countless accidents to finally get the stupid thing replaced with a new interchange.  Work didn't start until 2004, and it won't be complete, until 2008.   As it was, to "save money", our illustrious governor, reduced the funding that would have added an additional lane that it really could have used.

Another thought - I've often wondered if the wintertime plowing they do across the bridges and overpasses doesn't contribute to the wear and tear they get.  Those plows really dig in to keep the roads snow and ice free.  So much so, that you can see them throwing up sparks while they're plowing.

73,
Ellen - AF9J

[Bill, KD0HG]

Ellen, you *know* where the Tri-State toll money is going?- LOL

I have relatives in the Chicago area and I make it a point not to use any of the toll roads. Mostly because they soak out of state travelers just passing though paying cash tolls. Illinois residents using a transponder pay ~ half as much per trip with a discounted rate.

Good old I-80 works fine for me all the way from Denver to Chicago, then I pick up I-55, and not a penny of toll anywhere on it. But now with fuel at $3/gallon, my diesel pickup gets ~20 on the highway and my kid's Focus gets 30 MPG. That's $300 round trip in the truck and $200 in the car. Insane!

[AF9J]

Where's the money going from the Tri-State Tollway?  Hmmmm - lesseee, crooked politicians, and outrageous pet pork barrel projects?  NAhhhhhh!   If I can. I try to take US Hwy 41 to bypass the tollway, if I don't have to go much further south than Gurnee.  As it is, the first 10 miles or so, of I-94 in Illinois are not tolled roadway.  Afterwords - all bets are off.  I got soaked for $3 one time, just to use 5 miles worth of tollway, because I didn't know of an alternate route.

73,
Ellen - AF9J