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Monday, June 13, 2011

Target Field Collapses Due to Resonant Frequency of The Wave

MINNEAPOLIS (Bottom of the Fourth) - It has not been a good year for Minnesota's stadium engineers. First, the Metrodome's roof collapsed because of a large snow build-up, reportedly because engineers had "failed to account for the fact that sometimes there is snow in winter".

Now, just a few months later, the Minnesota Twins' less-than-two-year-old stadium Target Field has also collapsed, much more devastatingly. Last night in a game against the Texas Rangers, fans were frightened when the stadium began to rumble in the bottom of the 7th inning.  The oscillations grew in size for about 20 seconds before the foundations of the stadium began to crumble, and not long after the upper decks collapsed in on themselves, crushing countless hot dogs, beer cans and Twins hats in the process.

No footage was captured in the panic, but the collapse could have looked something like this

Scientists say the collapse was a result of The Wave, which had been started by drunk frat boys (as is generally the case) in the 7th inning. What made this wave unique, however, was its speed (or lack thereof). Last night's wave had a period of 1 minute and 26 seconds, meaning it took that much time to complete one revolution of Target Field.

(For reference, the average period of The Wave at the Metrodome was about 48 seconds, as documented here.)

As it happens, 1:26 is also the period of resonance of Target Field. This was a problem.

For the uninitiated, all structures have a natural frequency at which they vibrate as a result of their material structure. This vibration amplifies when an external action is performed at the same frequency - like pushing a child on a swing - and can cause major disasters when affecting large structures. Famously, the Tacoma Narrows Bridge collapsed because of wind-induced resonance, and the Angers Bridge collapsed when soldiers marched across at its resonant frequency. (The soldiers were French, obviously.)

Target Field lead engineer David Ruggiero was distraught, and dumbfounded. "The Wave was part of my calculations... I accounted for this... It shouldn't have happened..." Ruggiero had never imagined, apparently, that The Wave could circumnavigate the stadium at such a slow rate.

Ruggiero's team is now working to figure out how a Wave could be so slow. They had previously worked out a theoretical maximum of 1 minute and 10 seconds, but clearly there was a flaw in their calculations.

Ruggiero's colleague, Alessandro Ariza, believes the coefficient λ, or "lethargy factor" needs to be revamped for an appropriate population. "λ (the Greek letter lambda) was calculated by Arvydas Sabonis, a Lithuanian sociologist," explains Ariza, "but his number was based on a Lithuanian sample. We should have reworked the constant for our decidedly lethargickier populace."

Unfortunately for the Twins, given the aforementioned destruction of the Metrodome's roof, they will have to keep playing at Target Field while repairs are underway. The debris strewn about foul territory, suddenly uneven terrain, and lack of an outfield fence will be, like the hill in the outfield in Houston's Minute Maid Park, "just part of the game".

2 comments:

  1. Just thought you'd like to know that I had multiple students cite your article in a college physics research paper on resonant frequencies and engineering disasters! This was very well-written and convincing...especially to those with cursory knowledge of physics! As a baseball fan, and a science nerd...I applaud your efforts here. Keep up the good work!

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  2. Just noticed this comment. That's amazing. Thanks for letting me know!

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