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RE: Buildings seperation

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When I think about pounding I am reminded of a desk toy that is pretty common.
Five steel balls are suspended adjacent to each other on strings.
When you lift one ball and release it to strike the group, the middle three
remain stationary and the far end ball is launched to an equal height of the
initial release. When you lift four balls and release them to strike the one
remaining ball, the remaining ball is launched to a height approaching four
times the height of the initial release.

The point is, that energy is transferred between buildings when they impact.
And in most instances, the larger or more massive building is going to win.
Another comaprison is what happened to residences in the Marina District of San
Francisco during the Loma Pieta earthquake.  These residences are built
basically adjacent to each other for entire blocks.  After the earthquake, the
residences at each end of the block were pushed over, and the residences in the
middle had much less damage.  Just like the middle balls in the toy.

Engineers who look at pounding tend to focus on whether the floor levels of the
adjacent buildings are equal, so that one building is not striking against the
columns of the other.  But the energy transfer issue between more and less
massive buildings also needs to be considered.

regards,
Martin



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