Similarly the cantilever Forth Rail Bridge in Scotland, in operation for 127 years, is still soldiering on. The thing looks indestructible, but of course it has needed regular maintenance over the years.
The neighbouring Forth Road Bridge, a suspension bridge opened in 1964, fairly quickly went over the capacity it was designed for, and indeed it had to temporarily close recently for emergency repairs, causing traffic havoc in central Scotland.
Luckily the third Forth Bridge, the cable-stayed Queensferry Crossing, is just right next door and due to open in August 2017.
Yes, bridges and dams do have a life expectancy. I read that without proper maintenance, the Hoover Dam would collapse in roughly 10,000 years. The dam is really just a giant rock, built to be stronger than the natural rock surrounding it.
Bridges are a different matter. They are much lighter and can be susceptible to metal fatigue from the various cycles of weather and traffic. Or sometimes they just reach max capacity and are no longer economically viable to repair.
In the NY region, the Tappan Zee Bridge is being replaced by a new, larger bridge.
The Brooklyn Bridge underwent some sort of renovations about 5 years ago.
I paid that close attention, but I think by now the Pulaski Skyway and Bayonne Bridges have been repaired so many times they are basically completely new structures.
And I believe that the State is trying to secure funding to make sure the GW Bridge remains a nightmare for New York and New Jersey commuters into the next century.
That, of course, didn’t have much to do with any bridge getting old and wearing out. The bridge just basically collapsed during the catastrophic Loma Prieta Earthquake of 1989.
The nearby double-decker freeway in Oakland also collapsed – the upper deck fell onto the lower deck, squashing cars and occupants flat. Real-life pavement pizza sandwiches.
The 1940 Tacoma Narrows Bridge (a.k.a. “Galloping Gertie”) didn’t last 10000 years or even 10 years, nor even 1 year. Completed and opened July 1, 1940, collapsed November 7, 1940. Oops.
(I can’t view videos on this machine, so I’m not sure which of the many videos this is. The bridge was closed before it collapsed, but there was an inspector on the bridge at the time, in his car, with his dog with him. One video, maybe this one? shows him running for his life as the bridge collapses right out from under his feet. The car fell into the water and the dog drowned.)
No human life was lost in the collapse of the bridge. The only fatality was a cocker spaniel named Tubby who perished after he was abandoned in a car on the bridge by its owner, Leonard Coatsworth. Professor Frederick Burt Farquharson (an engineer from the University of Washington who had been involved in the design of the bridge) tried to rescue Tubby, but was bitten by the terrified dog when he attempted to remove him. The collapse of the bridge was recorded on 16 mm film by Barney Elliott, owner of a local camera shop, and shows Farquharson leaving the bridge after trying to rescue Tubby and making observations in the middle of the bridge. In 1998, The Tacoma Narrows Bridge Collapse was selected for preservation in the United States National Film Registry by the Library of Congress as being “culturally, historically, or aesthetically significant”. This footage is still shown to engineering, architecture, and physics students as a cautionary tale.
More specifically
The three legged dog in question was a black Cocker Spaniel left in the back seat of the lone car abandoned on the galloping bridge. The dog was owned by reporter Leonard Coatsworth, though his wife stated in an interview that it was her dog. (No doubt it went over really well when he told her he’d left the dog in the car when he abandoned it on the doomed bridge!)
On November 7, 1940, Coatsworth was attempting to drive across the four month old Tacoma Narrows bridge that at the time was the third longest suspension bridge in the world (today the 33rd longest). He was forced to abandon his car about 450 feet from the East Tower and a total of 1,895 feet from the Toll Plaza because of the extreme motion caused by a wind storm that had winds as high as 42 mph (69 km/h).
Three people attempted to save the dog, Coatsworth himself (no doubt thinking of the lashing he’d get when he got home and told his wife he’d abandoned her dog), a friend of his, Howard Clifford, and finally a man on the scene, University of Washington Engineering Professor F.B. Farquharson, who had arrived to observe the bridge’s motion.
In all cases, they were unsuccessful. However, in the the case of the brave professor, he actually managed to get to the car and even to get near the dog. But, as you might imagine, Tubby was in no state to let some random person pick him up and remove him from the car. As such, when the Professor opened the car door and attempted to grab the dog, Tubby snapped at him, managing to bite the index finger of the hand that was trying to save him.
Unable to secure the dog without bodily harm, Farquaharson left the car and the dog, returning to safety. None too soon either as a few minutes after Farquharson returned from his dangerous walk to save the dog, the bridge collapsed, sending the car and Tubby to a 200 ft fall into the Tacoma Narrows, which at that location had a depth of about 125 ft.
Six months later, Coatsworth was awarded $450 for the loss of his car and $364.40 for the contents of his vehicle for a total of $814.40 (about $13,000 today).
Definitely a myth for the Hoover Dam. There is an excellent book titled Colossus which deals with the construction of the Hoover Dam. Concrete was poured about an inch at a time, with workers standing in the concrete working it into crevices and corners.
Football stadiums are Berkerley university require rather dramatic repairs every few years… because they are built over an actual fault . (Baja ) California on one side, the USA on the other.
However things like bridges and dams are built with movement in mind.
with dams, they expect the substance of the hill beside it to also move, so as to not leave a significant gap. If a gap develops, they could caulk (or seal) the gap, or if required for structural strength, work on adding an extension that gives strength. Add a new wall downstream ? Basically when they add height to a dam, they have to make the buttresses bigger too … Vital to strengthen the buttresses downstream before adding the height.
The Tappan Zee Bridge over the Hudson River just over 25 miles north of NYC was built during 1952-55 and its deterioration required it to be rebuilt, with its new westbound span from NY to NJ opening to traffic last Saturday. The other new, eastbound, span will open around next June. Here is a link to a 4-minute video of its erection.
As for the new bridge to North Carolina’s Outer Banks, here’s a link to the erection of the Boner Bridge (sic) to replace one built in 1963:
the Tacoma Narrows Bridge collapsed because of a design flaw, as opposed to fatigue or just wearing out. IIRC, advanced construction methods at the time were used to give it a much thinner road deck than similar suspension bridges. What the designers didn’t account for was a stiff wind coming along, causing the deck to oscillate at it’s natural structural resonance frequency until it shook itself apart.
The Tappan Zee Bridge over the Hudson River just over 25 miles north of NYC was built during 1952-55 and its deterioration required it to be rebuilt, with its new westbound span from NY to NJ opening to traffic last Saturday. The other new, eastbound, span will open around next June. Here is a link to a 4-minute video of its erection.
As for the new bridge to North Carolina’s Outer Banks, here’s a link to the erection of the Boner Bridge (sic) to replace one built in 1963:
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I’m not sure I want to click all these links to Boners and erections.:eek:
