Tacoma Narrows Bridge – On July 1, 1940, after two years of construction, the first Tacoma Narrows Bridge was opened to the public. As soon as the bridge opened, it was noticed that it would twist and turn in even the smallest wind. People gave it the nickname, “Galloping Girtie.” Just four months and one week after opening, on November 7, 1940, the bridge collapsed during a 42-mph windstorm.
Tacoma Narrows Bridge Collapse (video 4:17)
Replacing the bridge – The collapse of the Tacoma Narrows Bridge was a hallmark in the history of bridge design and civil engineering. The remains, located on the bottom of the Sound, are a permanent record of man’s capacity to build structures without fully understanding the implications of the design and the forces of nature.
Tacoma Narrows Bridge – a pair of twin suspension bridges that span the Tacoma Narrows strait of Puget Sound in Pierce County, Washington. The replacement of the original bridge opened in 1950 and still stands today as the westbound lanes of the present-day twin bridge complex. Construction on a parallel bridge began in 2002 and the new bridge opened to carry eastbound traffic on July 15, 2007, while the 1950 bridge was reconfigured to carry westbound traffic.
At the time of their construction, both the 1940 and 1950 bridges were the third-longest suspension bridges in the world in terms of main span length, behind the Golden Gate Bridge and George Washington Bridge.
If p is driving frequency (powered by the winds), w is the natural freq. of the substance, then, if oscillation is not damped, then, disp.= Amplitude/p^2-w^2 X sin(pt+theta) Now, if p=w, then Amp obviously approaches infinity
- frequency, oscillation, dampening, amplitude, testing, wind tunnel
Challenges for you to work on…
- construct a model bridge that will twist like the original Tacoma Narrows bridge. What design changes are needed to prevent the twisting?
- Build a spaghetti bridge. 30 cm long span, 10 cm wide, max 20 cm high. Nothing but hot glue and spaghetti allowed. No more than 1/3 over lap allowed with spaghetti except for reinforced overlap at load points. Central loadpoint is easiest design, but you build others. Look up truss loading theory. Mass before destruction. Highest total weight divided by mass wins.