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Re: [Phys-l] Why soldiers break step on small bridges, and not so small.



Dancers have this problem, or rather the building owners have this problem
when they rent to dance groups. I used to dance on the third floor of an
old wood frame church building. You could actually see the floor go up and
down in time with the music. Underneath this room was a small wedding
chapel with a false ceiling. Every Sat after our dancing the maintenance
people had to sweep plaster dust off of the chairs. Finally the group was
banished to the gym in the basement when they had to sweep off the whole
plaster ceiling.

Ok, it may not have been a resonance effect, but normal out of step walking
did not stress the ceiling and cause plater to fall. In all fairness the
concealed plaster ceiling was at least 100 years old or even much older, so
it was probably time.

John M. Clement


A pedestrian bridge in Lubbock had this problem, vibration
when Texas Tech students marched in step on it (or rather,
partied in step) after/before some football games.

<http://lubbockonline.com/stories/040309/loc_425377816.shtml>