Talk:Tacoma Narrows Bridge

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isn't this why many bridges now have upper and lower levels, because of the added strength? Slrubenstein



  • I was under the impression that the new design doesn't twist in the wind because it is open and allows wind to flow through. Correct me if I'm wrong.

The original design was (relatively) smooth, like a sail, or an aeroplane wing. Refer to airfoils... The open truss means that passing air swirls turbulently preventing a smooth thrust - leading edge twisted up, force up on the smooth lower surface facing the wind, until the flex response forces the leading edge down, so a force down on the smooth upper surface; likewise on the back surface to the wind the airflow smoothly follows the surface, curving around the leading edge to do so and creating a low pressure that augments the high pressure on the wind-facing side in a nett force. With turbulent airflow, what would be the low pressure area is backfilled with turbulent air. Thus for example, sailors prefer to have no clutter near their sails, and sails with both sides smooth. NickyMcLean 20:58, 14 June 2006 (UTC)

  • This I don't know. I only know that bridges are now built to avoid the "twisting" that set up the resonance in the TNB. -- April
  • Resonance! Are we under the evil spells of entry-level physics textbooks? ;) TNB collapsed from simple aerodynamic instability, or at least I am writing a paper to support that argument. look at http://www.ketchum.org/ajp1.html ?

Contents

[edit] Simple logic says it was resonance

By simple logic and Mill's Canons, it was resonance. Since the wind still blows across Tacoma Narrows and the re-designed bridge now stands, the original bridge design must have been susceptible to resonance, and the structure weakened by the oscillations caused by the resonance. Have you in fact seen the film of Galloping Gertie?

I hope to god that the entry above was made in sarcasm. Are you SURE the new design works because it's "resonance-proof" or because it fixes a different problem?

The film clearly shows that the mode that destroyed the bridge was torsional, and was flutter. It also shows other modes, which were non-destructive and earned the bridge the Galloping Gertie nickname. That's why there's so much confusion out there. moink 04:57, 7 Dec 2003 (UTC)

[edit] blog comment

is the comment about the bridge being used in a blog logo really necessary? what purpose does it serve? --Rain 19:31, 20 May 2005 (UTC)

[edit] Picture?

What happened to the picture? Is someone working on replacing it? - Tεxτurε 21:17, 13 September 2005 (UTC)

I'm heading up to Seattle today. I'll stop by and take a photo on the way, hope the weather is nice. Cacophony 18:13, 21 January 2006 (UTC)


[edit] New Bridge

Why isn't there a picture of the bridge as it stands today? R'son-W 09:49, 7 November 2005 (UTC)

  • The current bridge from 1950 looks no different now than it did back then. The entire project has, however, changed dramatically due to the construction of the parallel bridge. I am thinking that upon final completion and renovation of both spans by 2008, then we can have a new default picture. Sherwelthlangley 19:37, 26 April 2007 (UTC)

[edit] Vandalism

"GUANDI WAS A GREAT PRESIDENT"? Correct me if I'm wrong, but that has just about nothing to do with the Tacoma Narrows Bridge. And I don't think it's "280999990 ft/8543550 m" long. What the balls?!


[edit] Tubby the dog

Be Jesus.. does that mean Tubby was deliberately left in the car? Tubbyy!- max rspct leave a message 03:04, 29 April 2006 (UTC)

[edit] Picture of collapse mirrored

For some reason the photograph of the collapse is a mirror image. If you compare the still to this film: http://www.youtube.com/watch?v=uzdQer1gvsU , around second 53, you'll notice it clearly. Does someone want to flip it?

[edit] Length of bridges

All sources agree on the length of the main-span—2,800 ft—for all three bridges.

But for the total length we have the following (all from official sources):

  • Bridge History – “…the [1950] bridge is 5,979 feet in length. That's 40 feet longer than its predecessor, Galloping Gertie.”

This would make the 1940 bridge 5,939 ft (5979–40)

This would make the 1940 bridge 5,000 ft. (2800+1100+1100)

The image on the last page also shows the 2007 deck longer than the 1950 deck. This makes me think that the full bridge deck lengths are 5,000 ft (1940), 5,040 ft (1950), 5,400 ft (2007), and that the 5,979 ft “length” for the 1950 bridge includes ramps etc. but I cannot find a definitive source. —MJBurrage • TALK • 16:18, 30 January 2007 (UTC)

[edit] Update

Because the second span is opening very soon, this article will need to be re-worked and new pictures added. I can re-word the article and incorporate the "2007" section into the lead, but I want to give someone who is more invested in this article a chance to do so. I'll come back in a few days and see if the "official opening" generates any activity on the article. Thanks. pinotgris 22:22, 14 July 2007 (UTC)

I've made several edits, hacking away a lot of crusty trivial bits, moving the new bridges to the top and Galloping Gertie down, adding a couple photos, and editing a bit (WSDOT's Flickr feed is cc-2.0! Sweet!). Please, make more edits!
BTW, I think that we can safely refer to both spans as "The Tacoma Narrows Bridge". That's what's done at Delaware Memorial Bridge. Travisl 18:57, 16 July 2007 (UTC)
Over all, I think this is a very good and much needed update -- thanks! One minor quibble: I would not call the 2 spans "Eastbound" and "Westbound", since I think they are going to shut down the "westbound" bridge for a while, pushing westbound traffic onto the eastbound. I prefer "1950" and "2007" to label them, since this is accurate and less dependent on the vagaries of DOT traffic management. Mlouns 19:06, 16 July 2007 (UTC)
I haven't heard anything about closing the 1950 bridge, but you make a good point that I went to check on. The WSDOT web page states:
“ A note on terminology. The first Tacoma Narrows Bridge, completed and destroyed in 1940, earned the nickname "Galloping Gertie." We use the "Gertie" label or "1940 Narrows Bridge." The bridge we drive over today was completed in 1950. We call this one the "Current Narrows Bridge." The new bridge now under construction and scheduled for completion in 2007 we refer to as the "2007 Narrows Bridge." ”
That's probably the same terminology we should use, but I'm out of time today. Go for it! Travisl 19:53, 16 July 2007 (UTC)

Regarding an attitude towards acceptable risk I am told by an instructor at south puget sound community college near the bridge recalls that his mpther told him that school kids from seattle were bussed south to watch the bridge wiggle during a windstorm. Now they would tell all the kids to stay home.

[edit] Quote Reference

Does anyone have a reference for the quote from Leonard? The bridge was closed to traffic well before its collapse, and there was significant time between the car appearing on the bridge and the actual collapse that the quote doesn't make sense. 32.97.182.171 18:42, 8 August 2007 (UTC)

[edit] Picture of New Bridge Added

I was at the bridge today doing some Geocaching and had my camera gear, so I took a panorama picture of the bridge and added it to a "gallery" section for the page. I think so far this is the only picture of the new bridge in its entirety, so even though the weather wasn't the best, at least there is a picture on the page now. If I'm in the area again and the weather is better, I'll try to do an improved shot. Rattlhed 23:41, 12 August 2007 (UTC)

[edit] transverse or longitudinal?

"Shortly after construction finished at the end of June (opened to traffic on July 1, 1940), it was discovered that the bridge would sway and buckle dangerously in relatively mild windy conditions for the area. This resonance was longitudinal, meaning the bridge buckled along its length, with the roadbed alternately raised and depressed in certain locations -- one half of the central span would rise while the other lowered. Drivers would see cars approaching from the other direction disappear into valleys which were dynamically appearing and disappearing."

That sounds like a transverse wave, not a longitudinal wave. -lethe talk + 23:24, 16 September 2007 (UTC)

I edited the article to say "transverse" instead of "longitudinal". Since I don't actually know what kind of oscillation Gallopin Gertie exhibited, and since that description along with the term "longitudinal" have stood on the article for almost 4 years without being corrected, and since the term was introduced by an MIT aerospace engineering PhD, I'd sure like to get a second opinion. -lethe talk + 23:39, 16 September 2007 (UTC)

[edit] For those of you who haven't seen this yet

An entertaining take on this article. Aviad2001 17:15, 24 October 2007 (UTC)

[edit] Causes of collapse are not well explained

It was a combination of more factors but one of the most important ones was not explained. User Slrubenstein is right - the bridge's transversal cross-section reveals two "I" beams connected with a SINGLE horisontal deck situated on top of them. While the "I" beams do catch wind as described in the article it was the LACK OF A SECOND DECK BELOW that caused the cross-section to roll when subjected to a flanking force which creates torsion or twisting of the bridge. The rolling happends because the cross section is not symetrhical in relation to the direction of the force. The CENTER OF STIFFNESS of that cross section is very far from it's center of gravity . If it had the second deck the bridge would just bend horisontally (with little or no twisting). Only after this comes the whole resonance story.

[edit] Leonard Coatsworth

Was Leonard Coatsworth an accountant (as described in front of his quote at the beginning of the "Collapse" section) or a "Tacoma News Tribute photographer" as described in the "Tubby the Dog" subsection? I doubt they are both correct, and having both facts makes reading the article somewhat interesting.- Enuja (talk) 00:17, 2 February 2008 (UTC)

[edit] Photo

Walking over the bridge today I saw this worker transport thing cruising along under the new bridge. I couldn't figure out where to put it in the article though, so if somebody else thinks it's worthwhile, feel free to put it in. Murderbike (talk) 00:58, 25 March 2008 (UTC)

There really should be a "Maintenance" section, but the only thing I'm finding in a quick search is [1], which was written before the second span was built (and which I can only see through Google's cache, for some reason). I know I've read human interest news stories in the past about the guys whose job it is to paint the bridge, and it's a year-round job. I don't know if anything's been written after the new bridge opened, though. Travisl (talk) 17:10, 25 March 2008 (UTC)

[edit] First toll in x years

The article currently states that the eastbound bridge has "the first roadway toll operation in Washington for nearly 20 years," citing a reference to the removal of tolls from the Hood Canal bridge in 1985. However, Astoria-Megler Bridge says that tolls were removed from that span in 1993. It could be argued that the toll booth was on the Oregon side. Bridge of the Gods (modern structure) is still an active toll bridge, operated by the Port of Cascade Locks. Similarly, Hood River Bridge is a toll bridge operated by the Port of Hood River. I've removed the statement again. Hopefully someone can clarify what it means. Travisl (talk) 21:08, 30 April 2008 (UTC)