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Are heavy vehicles destroying our bridges?

steverstever Posts: 52,462
Tidester was wondering wonder whether anyone would like to speculate on whether today's heavier vehicles may be contributing to more rapid deterioration of bridges and highways.

"This article says:

"... the average vehicle today simply weighs a lot more than it did then. In 1981, the average passenger vehicle weighed about 3,200 pounds. Today, thanks mostly to more SUVs and vans, the average vehicle weighs almost 4,100 pounds."

Surely, the engineers who designed the I-35 bridge in Minneapolis didn't anticipate such a load. Each traversal of a bridge by any vehicle has a microscopic effect proportional to its weight but that gets multiplied by 1 to 2 BILLION crossings over 40 years!"

I changed Tides' wording from vehicles to SUVs & trucks to make sure this new discussion got everyone's attention. :)


  • grbeckgrbeck Posts: 2,361
    ...tractor trailers may be destroying our bridges.

    But I would doubt that SUVs make much difference, as bridges have always been built to withstand much heavier vehicles (UPS delivery trucks, tractor trailers that were smaller than the ones used today, but still much heavier than an SUV).

    Using 1981 as a starting point is not quite fair. The great downsizing was still underway. Most of our infrastructure was not built in the 1980s. If anything, I remember articles in the 1980s worrying that the new downsized cars would not be compatible with the design of our roads and bridges (features designed to route a typical 1960s full-size car back on the road could flip a smaller 1980s car). Most of our infrastructure was built using the 1960s full-size car as the standard.

    The bridge that collapsed in Minnesota, for example, was completed in the late 1960s.

    In the 1960s, Cadillacs and Lincolns topped out at over 5,000 pounds, and the biggest Buicks, Oldsmobiles and Chryslers weren't far behind. The most popular vehicles were the Chevrolet Biscayne/Bel Air/Impala/Caprice and Ford Galaxie/LTD, which were hardly feather weights.

    Heavy vehicles are hardly anything new.

    If anything, heavier use by all vehicles is probably contributing to the more rapid deterioration of bridges and highways. Traffic volumes keep going up, up, up.
  • iluvmysephia1iluvmysephia1 Alamogordo, NMPosts: 7,615
    and this toll on bridges is affected by the fact that more 16 year-olds join our ranks as drivers every year than 85 year-olds that stop driving. Year after year after year the counts go up...that's bound to take a toll on bridge poundings.

    Being a Pacific Northwesterner originally I have watched the footage of the Tacoma Narrows Bridge's collapse 60-odd years ago. That was engineering error to not take in to account the harrowing winds of the Narrows. My Grandpa lived on the other side of the rebuilt Narrows Bridge in a little community called Gig Harbor. Truly a beautiful place and it's a pretty view down below from the rebuilt bridge as Dad would drive this way to get us to Grandma and Grandpa's house.

    2011 Kia Soul Sport 5-speed

  • euphoniumeuphonium Great Northwest, West of the Cascades.Posts: 3,425
    The bridge was a truss-type bridge, where the deck the traffic travels on is on top of the truss. It is a structural concept very similar to the bridge across the Columbia at Longview and those on I-5, both north and south of Longview. Except on those structures the bridge deck is connected to the bottom cord of the truss and the traffic travels through the structure. Placing the structure on the top cord of the truss allows easier cross-connection between the two main trusses of the bridge, making a lighter, but stronger structure. (The cords of a truss are the top and bottom members that form the outline of the truss.) Trusses generally use a series of triangles as the connection of three members in the shape of a triangle is a fairly stable structure.

    Problems with truss construction usually occurs at the joints where three or more members connect. Usually the connections are a series of plates used to make the connections using rivets (old construction), bolts (Most likely for the Minneapolis bridge) and welding (More modern construction) to connect the plates as they lap on the sides of the main structure members. This would be similar to joining two sheets of paper end to end, using scotch tape on each side to connect them. The paper would be the structure, the tape would be the side connecting plates. The problems with the truss connections is that there can be corrosion in between the plate and member that is not visible from looking at the connection as they inspect. This would require using test equipment of some kind - ultrasound for one. Welds can be inspected with x-rays, but this is expensive. Also micro-cracks can develop in the connecting plates or even in the main structure that can't be seen by the naked eye. These can be generated and enlarged by the passage of traffic.

    Looking at the sequence that shows the bridge collapsing, I got the feeling that the bottom cord was the item that failed. The bottom cord is in tension, which means it is being pulled apart. Top cords are in compression - if you try to pick up four books by pressing against the side of the books, instead of supporting from below, you are compressing the books to form a single unit. Compression failures are usually distorted. There was no major distortion until the structure hit the ground. Tensile failures will talk and make noise before they break, but the break is very sudden. With the normal traffic noise I doubt that anyone would have heard are recognized that a failure was about to happen.
  • wlbrown9wlbrown9 Posts: 867
    About 15 years ago, Arkansas/Mississippi/Tennessee still had 72,000 truck weight limits...everywhere else had gone up to 80,000 lbs. Much lobbying and predictions that keeping the low limits would hinder commerce. Eventually the truck industry was successful in getting the limits raised. That extra 8,000 might be rougher on the highway and bridge network than a couple hundred pounds on a passenger vehicle.

    Anyone know the history of (US Highway & Interstate) truck weight limits?
  • steverstever Posts: 52,462
    There's some history in this link from Hendrickson USA. Some good diagrams there too about axle weight and the difference a heavy short truck makes vs a heavy long truck.

    And we've tweaked the title a little so we don't pick on Hummers too much - I trust we didn't lose anyone.
  • fezofezo Manahawkin, NJPosts: 10,376
    What? Hummers aren't heavy vehicles? :P

    What really hurting our bridges, along with our roads, water systems and anything else in the infrastructure is the insane lack of maintenance. You can see the difference when you hit that rare piece of work that actually IS maintained well. The Golden Gate Bridge is one that amazes me. The thing is over 70 years old and looks like they just built it. There is always someone painting it.

    Over where I am I'm not sure of the reason but the difference between two of the bridges going for New Jersey to Philadelphia is striking. The Walt Whitman looks fine. The Ben Franklin looks like it is going to rust away. I don't get it.

    I suspect that roads and bridges that have to pay their own way do better even though I am loathe to give anyone any ideas about more tolls and the Ben Franklin example would certainly not back this up. I think of things like the Garden State Parkway, George Washington Bridge and the Whitestone Bridge.

    Meanwhile, practically new sections of Route 287 are falling apart and I shudder to think about the Tappan Zee - a truly beautiful structure that has been left to rot with a ton of traffic.
    2015 Mazda 6 Grand Touring, 2014 Mazda 3 Sport Hatchback, 1999 Mazda Miata 2004 Toyota Camry LE, 1999.
  • lemkolemko Philadelphia, PAPosts: 15,306
    The Ben Franklin Bridge is also much older than the Walt Whitman. The Ben Franklin Bridge was built in 1926 and the Walt Whitman in 1957. Before the Ben Franklin Bridge, Philadelphians relied on ferry service to get to Camden, NJ.
  • fezofezo Manahawkin, NJPosts: 10,376
    Good point, but I still wonder why they can't do basics like paint the Ben Franklin. Structurally it is a pretty bridge but it definitely needs work.

    They still had ferrys going across the Delaware into the 60s in Wilmington. I remember going across the bridge that is now there when they were still building the second span.
    2015 Mazda 6 Grand Touring, 2014 Mazda 3 Sport Hatchback, 1999 Mazda Miata 2004 Toyota Camry LE, 1999.
  • lemkolemko Philadelphia, PAPosts: 15,306
    I believe a huge repainting project for the Ben Franklin is already in the works. I read that it costs something like $40 million to do the job and is the job of the Port Authority.

    Of the other major bridges - the Betsy Ross Bridge opened for traffic in 1976, the Commodore Barry Bridge in 1974, and the Tacony-Palmyra bridge in 1929.
  • tidestertidester Posts: 10,059
    Most of our infrastructure was built using the 1960s full-size car as the standard.

    The 1980 date just happened to be the date used in that particular article. As for the 60s, even though there were some monster cars in terms of weight, the average weight of passenger cars was just over 3,000 pounds. In fact, the average weight of passenger cars has decreased over that period but proportionally far more people are driving SUVs and pickups than the engineers ever imagined.

    tidester, host
    SUVs and Smart Shopper
  • fezofezo Manahawkin, NJPosts: 10,376
    Whoa! Now that and the Burlington-Bristol Bridge are real adventures!
    2015 Mazda 6 Grand Touring, 2014 Mazda 3 Sport Hatchback, 1999 Mazda Miata 2004 Toyota Camry LE, 1999.
  • kernickkernick Posts: 4,072
    I would prefer a bridge that lasted a long time and didn't need much maintenance.

    Have you ever noticed that ancient structures lasted for hundreds or even thousands of years. Why was that? What is the lifespan of our modern structures? I know in Boston the elevated highway was 40-50 years old and crumbling. It takes 15 years and $20B to replace it. How long are the new tunnels and bridges going to last? I hope not just 40 years!

    Maybe we should question whether regular steel and concrete are the best building materials. Replace their use where possible. Once steel is delivered to a building site, and put at the site, you start getting corrosion even before the steel is up. That doesn't bode well for long-life.

    But I believe a lot of the construction attitude in this country is that we'll just replace it and that creates a lot of jobs, and chances for corruption to skim from the projects.

    I'm afraid we have too much of a throw-away philosophy, that is now a paradigm of policy.
  • cooterbfdcooterbfd Posts: 2,770
    This would require using test equipment of some kind - ultrasound for one. Welds can be inspected with x-rays, but this is expensive.

    Well, where are our gasoline taxes and tolls going??? To Iraq??? I know here in RI, where we pay some of the largest STATE gas tax in the country, it is SUPPOSED to fund road repairs. Most of it ends up in our general fund, to be spent elsewhere. If the feds and other states do this, it's not fair. This money should be spent on repairs, new infrastructure, and public transportation ONLY!!!!
  • kernickkernick Posts: 4,072
    I just paid $300 auto registration tax to my city yesterday. I also did the state registration, which is what pays for the plates and paperwork. The city tax - by far the larger, goes to the general fund.
  • fezofezo Manahawkin, NJPosts: 10,376
    "But I believe a lot of the construction attitude in this country is that we'll just replace it and that creates a lot of jobs, and chances for corruption to skim from the projects."

    Precisely so. Big shiny capital projects are much sexier to show off to the folks at home than periodic inspection and maintenance would be. I mean which do you notice more, a big building project of a few guys painting?

    Of course a couple of the most impressive bridges are the ones that ARE older and maintained. I already used the Golden Gate as an example. The George Washington is another.
    2015 Mazda 6 Grand Touring, 2014 Mazda 3 Sport Hatchback, 1999 Mazda Miata 2004 Toyota Camry LE, 1999.
  • roadburnerroadburner Posts: 12,248
    I blame Rosie O'Donnell and Queen Latifah- and whoever keeps them supplied with Twinkies.

    Mine: 1995 318ti Club Sport; 2014 M235i; 2009 Cooper Clubman; 1999 Wrangler; 1996 Speed Triple Challenge Cup Replica Wife's: 2015 X1 xDrive28i Son's: 2009 328i

  • fezofezo Manahawkin, NJPosts: 10,376
    Good point. I knew there was a way to blame this on Rosie. I Queen Latifah is a harder one for me. Rutgers alum....
    2015 Mazda 6 Grand Touring, 2014 Mazda 3 Sport Hatchback, 1999 Mazda Miata 2004 Toyota Camry LE, 1999.
  • 0patience0patience Oregon CoastPosts: 1,712
    You must be in my neck of the woods to be talking about the Longview (Lewis & Clark) bridge.

    I was surprised to hear that 7 years ago, that bridge was inspected and they didn't do anything since then.
    I may have heard it wrong on the radio, but that seemed odd.

    Oregon is constantly inspecting the bridges.
    They have trucks with special cranes that swing down over the side and the inspectors can view the underside of the bridge and inspect it.
  • gagricegagrice Pahrump, NevadaPosts: 31,432
    I'm afraid we have too much of a throw-away philosophy, that is now a paradigm of policy

    I think that is exactly correct. It makes no difference if it is a car, computer or bridge. I watch the strip malls going up in So. CA. They are pathetic examples of horrible construction. They will be gone in 20 years for sure. Wonder if the pyramids were built like the I35 bridge over the Mississippi river. All we know how to build is for the short term. I wanted to build an adobe home. I see adobe homes in Mexico that are 300-400 years old and still standing. No that is not compatible with current building standards.

    Yeah, the city wants a house that falls apart in 20 years so they get more taxes on the rebuild.

    The authorities reviewed the safety record of the bridge, which had been designated “structurally deficient” as early as 1990. More than 70,000 bridges across the country are rated structurally deficient like the I-35W bridge, and engineers estimate repairing them all would take at least a generation and cost more than $188 billion.

    That's the approximate number of bridges that are either "deficient" or "obsolete," according to the American Society of Civil Engineers.


    That's more than one in four.

    Approximately 73,000 of them are "structurally deficient" - like the bridge in Minneapolis - while 80,000 others are "functionally obsolete." That means they're carrying more traffic than they were designed to carry.

    Not scary enough? Then try this quote on for size: "I think we're going to see bridges collapse, and we do on a regular basis," said Kent Harries of the University of Pittsburgh's School of Engineering.

    London bridges falling down
  • toro52toro52 Posts: 1
    My last trip to Italy I drove over a bridge the Romans built 2000 years ago..maybe the engineers should look at their blueprints..Toro52
  • gagricegagrice Pahrump, NevadaPosts: 31,432
    As smart as we think we are, we could learn from engineers that were around 5000 years ago. I am sure many of our bridges were built by low bid contractors and brother in law deals.

    It reminds me of a question posed to old Mayor Daley. Why did your son in law get the contract? Mayor Daley popped right back with "What Kind of Man Does not Look out for His Own Kin".

    So we have a lot of bridges built with substandard materials and maybe unskilled labor.
  • cooterbfdcooterbfd Posts: 2,770
    maybe unskilled labor

    I don't know about that up here in the northeast. Most, if not all jobs are union, so they are skilled. Now I know that on the Big Dig in Boston, there was talk of using a lower grade or watered down concrete for the tunnel tubes (now they leak) and questions about the method used to fasten the concrete ceiling tiles and the final inspection of them prior to opening it (one fell on a car killing a young lady).
  • steverstever Posts: 52,462
    A lot of the bridges built since WWII were designed for a 50 year lifespan. Plenty, right?

    Fugit inreparabile tempus.
  • fintailfintail Posts: 48,086
    And with real incomes stagnant at best, and materialism taking more control than ever, people will be very unwilling to pick up the tab for replacements or repairs.

    The future is going to be a mess.
  • tidestertidester Posts: 10,059
    If you are on a bridge when it collapses, are you more likely to survive in a car or an SUV? From the TV reports, I saw a lot of SUVs out there.
  • gagricegagrice Pahrump, NevadaPosts: 31,432
    Good question. I would say an old VW bug. They would float. You may end up in St Louis, cold, hungry and tired.

    I think the NHTSA will have to add a new safety test. Bridge collapse worthiness.
  • kurtamaxxxguykurtamaxxxguy Posts: 1,798
    Having lived in S. Calif. 25 years, I can vouch the heavy truck traffic has dramatically increased (possibly double) over those years.
    Many bridges have been reinforced for earthquakes, but this is for side-side sway and road joints from separating or sliding off the pylons.
    Some bridges are being rebuilt as they are widened, but there are some (several on the 710 freeway, a __major__ carrier of truck traffic) that are deficient.

    Then again, a recent visit to Portland, Oregon revealed an astonishing number of badly maintained bridges on the I-5 and elsewhere.
  • tidestertidester Posts: 10,059
    Bridge collapse worthiness.

    Or, perhaps, SCUBA gear in every vehicle?

    I've been wondering about all these people we have been watching giving interviews on TV. They tell us they were in free fall during the collapse - like 40 to 60 feet free fall - and yet they are able to talk about it? How much of a role did their vehicle type play in their survival?
  • tidestertidester Posts: 10,059
    (possibly double)

    At least. The population of California has just about doubled in 40 years.
  • john500john500 Posts: 409
    I've seen some references to the Philadelphia area in this thread. In the NY-NJ-Pa area, all bridges over the Delaware River and Hudson River are controlled by either the Delaware River Port Authority or the Hudson River Port Authority. When one calculates the amount of money that has been collected via tolls, it can easily be seen that the collected toll value represents the cost of several total bridge constructions over 20 years. It would be completely inexcusable for any of these bridges to fail. If any of these bridges ever should fail, the first action should be to hold all members of the Port Authority criminally liable for negligence. I'm not familiar with the organized crime (i.e. quasi-government) practices in Minnesota.
This discussion has been closed.