expansion jointsseismic joints

huangyhg

expansion joints/seismic joints
  is everybody else allowing enough of a gap in roof thermal expansion joints (example in single story metal deck) to satisfy the seismic joint code requirement as well. i don't usually see this done. since the buildings are acting separately perpendicular to the joint, i think a seismic joint would be required.
  also, is a seismic joint required when 2 buildings that have the same period are next to each other. for example, i am separating 2 buildings by a firewall. each building butting up against the wall and not connected. if each building is moving at the same period, can they still theoretically smash together in an earthquake?