Tuesday, January 25, 2011 2:57:51 PM
@crakrjak: a 6 to 10 foot piece of concrete is not going to flex. Same could be said of anything of short enough length. take a 6" diameter steel rod 6" long and try and flex it. Now make it 6'. Now make it 60`. Anything long enough will flex. And that is designed into skyscrapers. They are not one huge piece of concrete. Concrete has been around a long time. That is why building height was limited until they started using steel frames (which do flex).
As for vibration being only up and down, that would be like saying the train only pushes down on the tracks. Living next to a train track, I`m sure you know that there is random side to side motion, just like I`m sure you know that the conical shape of the wheels keeps the train from flying off the track.