seismic separation for suspended ceilings

huangyhg

seismic separation for suspended ceilings
hello-
we have an agency enforcing the requirement than ceilings over 2500 sf have a seismic separation joint with a gap determined by the designer?  i can't seem to find anything on that.  any experience out there?  thanks.
rd78
fema 302, paragraph 6.2.6.2.2.d.
yes, i'm aware of where the requirement is stated (ref'd asce 7).  my interest is in how it is implemented?  how is the size of the gap determined?  is there an aspect ratio requirement, or does anything under 2500 sf meet the requirement?  thanks.
rd78
if you read that section in fema 302, it gives specific separation joint criteria.
"the width of the perimeter supporting closure angle shall be not less than 2.0 inches (50 mm). in
each orthogonal horizontal direction, one end of the ceiling grid shall be attached to the closure
angle. the other end in each horizontal direction shall have a 3/4 inch (19 mm) clearance from the
wall and shall rest upon and be free to slide on a closure angle."
there is no aspect ratio mentioned.  i suspect this is because the requirement for the separation is based on the weight of a 2500 sf ceiling which is the same regardless of which direction your going.
a recent client met the suspended ceiling seismic requirement by selecting a suitable grid system. here is information on the armstrong brand
armstrong's detail for the gap shows 6".  i just wanted to know how that was determined.  the armstrong rep indicated they believe they meet the requirement with this standard gap design.
you can also check out usg grid systems.