220
The Service Module: Service Bays
The service bay will provide some of the shear walls for the overall
seismic resistance of the structural frame. It will also normally be bounded
by two-hour fire partitions (or shear walls) as it always occurs at the
boundary of a fire section and also contains special hazard areas.
223.2
VARIATIONS
The organization of service bays described above will be typical for
service modules generated from two-aspect space modules and for most
other conditions. But there are two important variations:
223.2.1
Split Service Bays
Service modules based on four-aspect space modules will necessitate the
use of a split service bay giving an external aspect to the bedrooms
between the equipment rooms. Figure 220-4 shows a typical arrangement
for this variation. Modules of this type are all comparatively wide; the
illustration is based on two bays of 49'6". The service crossovers in this
case will take place in an accessible exterior housing placed between the
equipment rooms at the service zone level.
223.2.2
Internal Service Bays
The second major variation occurs in large hospital configurations where
some service bays must be placed in an internal position between service
modules. (See Figure 220-5.) Three special conditions arise in this
situation. The first is the omission of the escape stair, as the service bay
becomes part of a horizontal exit between the service modules lying to
either side. The second condition is the requirement for a maximum width
of access between the two functional zones to facilitate circulation. The
third condition is the problem of providing outside air to the air-handling
units. As discussed under Section 340, the preferred solution is to place
these units at roof level and duct down supply air to the service module.
This means that the area originally containing the mechanical room
becomes a set of supply duct shafts to the various floor levels. In a
moderate-rise building these will take up less floor area than a mechanical
room and therefore leave more space for the circulation access described
above. Where a group of internal service bays are lined up through a
building configuration, this is referred to as a service strip. (See Section
411.6.3.)
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