[berettafan]

Originally Posted by competentone

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.

saw that on a Mythbusters. really interesting theory.