Failure of highway sign in Calgary
Failure of highway sign in Calgary
(OP)
Well, not exactly "news" but video of an instructive sign failure I found while trolling the yous-tube. At the very end you can see the guy catches a panel dropping off the tube frame.
http://www.youtube.com/watch?v=rbtoeiP6Jwo&fea...
http://www.youtube.com/watch?v=rbtoeiP6Jwo&fea...






RE: Failure of highway sign in Calgary
I have seen similar effects in the Edmonton area, but the exact explanation for it is beyond my ability to explain.
BA
RE: Failure of highway sign in Calgary
This is called Areodynamic Resonnance !
RE: Failure of highway sign in Calgary
I am sure it reminds most of us of the Tacoma Bridge failure, which Wiki explains it as:
The bridge's collapse had a lasting effect on science and engineering. In many physics textbooks, the event is presented as an example of elementary forced resonance with the wind providing an external periodic frequency that matched the natural structural frequency, though its actual cause of failure was aeroelastic flutter.[1] Its failure also boosted research in the field of bridge aerodynamics-aeroelastics, the study of which has influenced the designs of all the world's great long-span bridges built since 1940.
RE: Failure of highway sign in Calgary
I think the difficulty of predicting such resonant responses, let alone building in defenses against them, is the primary reason why highway-spanning signs are (in the regions I frequent) more commonly supported by three-tube or four-tube trusses with a _lot_ of diagonal tube bracing.
Mike Halloran
Pembroke Pines, FL, USA
RE: Failure of highway sign in Calgary
maybe someone in aerospace will chime in :)