320
Ceiling: Generic Design Options
The spacing of the tees is based on the assumption that the layout of
partitions and penetrations through ceilings will be greatly simplified if
the platform grid and the structural grid are made to coincide, since
they are so close. However, this is not essential.
When partitions occur parallel to and between two truss tees, it may be
necessary to fix 16-gauge straps between the tees at approximately
3'0" on center for fixing heavy doors or partitions carrying heavy loads
such as lead lining.
322.1.2
Precast Lightweight Concrete (Figure 320-4)
Precast lightweight concrete panels would meet the performance
requirements for platform strength, acoustic isolation and fire safety.
However, special consideration in joint details would be necessary to
eliminate the need for diagonal bracing in seismic zones. Special
equipment is necessary to make holes, and patching to full original
strength is difficult. Both the direct and indirect costs (greater weight)
are higher than those of poured reinforced gypsum.
322.1.3
Dry Gypsum Systems (Figure 320-5)
Dry gypsum systems are not quite as economical as poured reinforced
gypsum, but they would eliminate the drying out time required for
poured gypsum. An example of a dry gypsum system is illustrated in
Figure 320-5. This system utilizes 1"x24"x8'0" laminated "coreboard"
panels, similar to U.S. Gypsum's "shaftwall". The system is currently
under development by U.S. Gypsum. If testing is undertaken for
diaphragm action and for fire resistivity, and if these are successful, it
may be that the coreboard system becomes the preferred option in the
future.
322.1.4
Fire Protected Metal Decks (Figure 320-6)
Included in this category are assemblies using corrugated steel decks
or expanded metal panels which meet the strength requirements of the
platform, and materials suspended below the metal deck to satisfy
other requirements such as sound attenuation and fire resistivity. This
latter material might be a proprietary fire-rated ceiling system or simply
two layers of 5/8" gypsum board and appropriate sound insulation.
The major disadvantages are the overall depth required, the difficulty in
repairing holes and the need for diagonal bracing between hangers.
1 - 144
Previous Page
