Quote:
Originally Posted by CurtEgerer
I highly doubt a standard 60 or 90-pound jackhammer on the pavement could have triggered this (unless the deterioration of the steel framing was incredibly severe). Compare that to the resonance from, say, several fully loaded semi-tankers or cement trucks bouncing across this thing at 70MPH day in and day out. But who knows at this point? If there were, indeed, "out-of-plane girders" all normal assumptions can be thrown out the proverbial window.
|
Yes, one would need to consider all the stresses the bridge has been under, but on "resonant destruction": Consider something like Tesla's oscillator. Or "soldiers marching in unison across a bridge." It's not the "brute force" that is doing the destruction when resonant frequencies destroy something. It is the build-up of wave energy -- the super-imposition of the compressions and rarefactions of the waves moving through a structure -- which fatigues the materials and causes the failure.
It would be a "freak" occurrence if the jack-hammer use did set up resonant frequencies in the structure, but something I wouldn't ignore as a possible factor this early in the investigation.