Puente Arcos de Alconétar Vibración 1

Vídeo del movimiento del arco en construcción debido a fenómenos dinámicos originados por viento.

[@michaelmello42]

Timing with my iPhone stopwatch while counting the number of in-plane oscillations of the arch reveals a vibrational frequency of nearly 0.7 Hz. Applying the Strouhal Number (St = f*D/U) @ St=0.2, with an arch face width of D=2.4m, and assumed wind speed of 30km/hr (8.33 m/s) predicts a vortex shedding frequency of f=0.69 Hz. This is a stunning visual demonstration of vortex-induced vibration. Many well-documented engineering modifications followed, which effectively mitigated this problem,

[@lyndontrombley1970]

Once the bottom deck is in place the structure has a very different natural frequency (sqrt of K/M)) so with a minor modification to change the response to wind excitation it is probably as safe as any bridge. Moral of the story is be very cautious when you drive or walk under a structure being constructed as this is the most dangerous time to do so.

[@mybluemars]

This bridge did get built and put into production. The situation was resolved by welding metal flaps or deflectors along the edge of the arch ribs. It is also know as the Tajo River Bridge. See more here: www.highestbridges.com/wiki/index.php?title=Tajo_River_Bridge

[@johnnyllooddte3415]

looks ok to me..lets keep building hahahhaa

[@sebastianvega4126]

¿él puente se encuentra hoy en funcionamiento?

[@Emilioarevalo]

+Sebastian Vega El puente está actualmente en funcionamiento. Puedes verlo en el siguiente enlace: goo.gl/UeWatl

[@sebastianvega4126]

+Emilio M. Arévalo Hernández y el movimiento se dio por la fuerza del aire?

[@Emilioarevalo]

Efectivamente. Se necesitó un viento muy constante, perpendicular a la estructura y no a mucha velocidad, 24 km/h, para que la estructura entrara en resonancia.

[@bollonga]

Emilio M. Arévalo Hernández Buenas, dispones de alguna información técnica? Geometría de la sección de los arcos, frecuencias y formas modales, velocidades de viento o sólo ocurrió a 24km/h? Muchas gracias!

[@Emilioarevalo]

El puente es del Ministerio de Fomento. No dispongo de la información que me dices. Y sí, ocurrió para esa velocidad según me cuentan.

[@williamchappell4400]

como se dice photoshop

[@Emilioarevalo]

+William Chappell No hay photoshop ni nada. Es un vídeo absolutamente real de un fenómeno perfectamente estudiado y publicado. goo.gl/UeWatl

[@bollonga]

VIV (Vortex Induced Vibration) at a close enough frequency to natural vibration frequency (maybe 2nd mode?) of this arch, so excitation (vortex caused by moderate wind) gets into resonance with the structure.

[@luismorenolopez9672]

@@bollonga 3rd mode along the itself plane with 11.8 Hz frequency

[@johnnyllooddte3415]

ok..and that didnt make you STOP and redesign..you just kept going forward...hahahaha and you really think this will survive 50 years hahahah

[@bollonga]

All structures have vibration frequencies and vibration shapes, the more slender the structure the lower the frequency and the more prone to wind interaction with wind. That happens in Skyscrapers too quite often. 2D sections have a vortex shedding (you can google it) frequency dependant on the shape and the wind speed (or water flow speed or any other fluid, yes, gases behave as fluids in these matters). If these frequencies get close enough the structure can experience large movements. This can be easily avoided by modifing the section geometry (as I've read it was the adopted solution) or using a structural damper. I don't know the details of the project but it has happened on a construction stage, the final vibration frequency of the structure will probably be different so maybe the problem get solved. However, I agree this problem should be studied at a design stage and not "discovered" at a construction stage.