Een mooi voorbeeld van resonantie: de Tacoma Narrows Bridge wordt door windstoten in resonantie gebracht en zal het niet overleven!

Het volgende artikel is afkomstig van de website van Carleton University. Niet vertaald maar toch heel interessant. Let op! Na het bekijken van de foto's of films moet je terug met de knop van de browser, boven in het scherm. Bekijk vooral de spectaculaire Videoclip!

Meer informatie over resonantie vind je op het Spiekbriefje.

Stuart Doole was a former postdoc working with John Hogan on the dynamics of a piecewise linear model of a suspension bridge. Part of the motivation for this work was to provide a simple dynamical-systems explanation of the bi-stability and transition between modes observed in the famous collapse of the Tacoma Narrows suspension bridge

This page provides a mirror to the information held at Carleton University  Civil Engineering Exhibits Centre about the failure of the Bridge at Tacoma Narrows in May 1940.

On November 7, 1940, at approximately 11:00 AM, the first Tacoma Narrows suspension bridge collapsed due to wind-induced vibrations. Situated on the Tacoma Narrows in Puget Sound, near the city of Tacoma, Washington, the bridge had only been open for traffic a few months.

Contents

• Photos
• Mpeg video clip
• Full footage

The following images and captions were taken from the report:
Smith, Doug,
A Case Study and Analysis of the Tacoma Narrows Bridge Failure
99.497 Engineering Project,
Department of Mechanical Engineering, Carleton University, Ottawa, Canada, March 29, 1974.
Supervised by Professor G. Kardos.

Figure 6
This photograph shows the twisting motion of the center span just prior to failure.

Figure 7
The nature and severity of the torsional movement is revealed in this picture taken from the Tacoma end of the suspension span. When the twisting motion was at the maximum, elevation of the sidewalk at the right was 28 feet (8.5m) higher than the sidewalk at the left. Note the target at the left used by Professor Farquharson in making his observations.

Figure 8
This photograph actually caught the first failure shortly before 11 o'clock, as the first concrete dropped out of the roadway. Also note bulges in the stiffening girder near the far tower and also in the immediate foreground.

Figure 9
A few minutes after the first piece of concrete fell, this 600 foot section broke out of the suspension span, turning upside down as it crashed in Puget Sound. Note how the floor assembly and the solid girders have been twisted and warped. The square object in mid air (near the centre of the photograph) is a 25 foot (7.6m) section of concrete pavement. Notice the car in the top right corner.

Figure 10
This photograph shows the sag in the east span after the failure. With the centre span gone there was nothing to counter balance the weight of the side spans. The sag was 45 feet (13.7m). Also the immense size of the anchorages is illustrated.

Figure 11
This picture was taken shortly after the failure. Note the nature of the twists in the dangling remainder of the south stiffening girder and the tangled remains of the north stiffening girder.

Figure 12
The top left picture shows the center span diagonal ties and their connections. The top right picture shows the slackening of the tie due to twisting. The bottom left picture shows the frayed main cable after failure. About 600 (sic) wires are cut. The bottom right shot shows the diagonal ties after the failure.

Figure 13
This picture shows the buckling of the suspended floor system near the centre of the side spans. The top right picture shows the suspender connections and the type of cables used for this connection.

Figure 14
This picture shows the size of the towers and the type of construction used. There is a slight buckling of the tower as a result of the additional strain caused after the centre span collapsed. The towers were made out of structural carbon steel.

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This  video clip is an excerpt from the famous black and white movie. It is a short (250 frames) but biggish (684K) MPEG format clip. It shows maximum torsional motion shortly before failure. 

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The official source for video tapes about the Tacoma Narrows Bridge Collapse (1940) is:

Ed Elliot
The Camera Shop
1007 Pacific Avenue
Tacoma, Washington
USA 98402
ph: (206) 627-4159
fax: (206) 627-6107

The video is about 20 minutes with no sound, lots of good pictures of actual bridge bouncing away and collapsing, as well as scale model tests. The picture quality is fair.

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