Building Design and Construction Handbook - Merritt - Ventech!

VERTICAL CIRCULATION 16.23
enclosure should have a 2-h fire rating, and hoistway doors and other opening
protective assemblies should have a 1 1 ⁄2-h rating. Where fire-resistant construction
is not required, laminated-glass curtain walls or unperforated metal, such as 18-ga
sheet steel, should enclose the hoistway to a height of 8 ft above each floor and
above the treads of adjacent stairways. Openwork enclosures may be used above
that level, if openings are less than 2 in wide or high.
At the top of a hoistway, a concrete floor should be provided (but is not necessary
below secondary and deflection sheaves of traction-type driving machines
located over the hoistway). If a driving machine is installed atop the hoistway, the
floor should be level with or above the top of the beams supporting the machine.
Otherwise, the floor should be set under the overhead sheaves. The floor should
cover the entire top of the hoistway if its area would be 100 ft 2 or less. For larger
hoistway cross-sectional areas, the floor should extend from the entrance to the
machine space, at or above the level of the platform, for a distance at least 2 ft
beyond the general contour of the driving machine, sheaves, or other equipment.
In such cases, exposed floor edges should be protected with a toe board at least
4 in high and a railing at least 42 in high and conforming to the requirements of
the ‘‘American National Standard Safety Code for Floor and Wall Openings, Railings
and Toe Boards,’’ ANSI A12.1.
16.7.2 Venting of Hoistways
In significant high-rise-building fires, the elevator hoistways have served as a flue
for smoke and hot gases generated by fire. The prevailing thought has been that
hoistway venting means could minimize the spread of smoke and hot gases throughout
the building. As more has been learned about smoke movement in high-rise
buildings, many alternatives have been developed to prevent migration of smoke
from the fire floor to noninvolved floors of the structure. Among these alternatives
are various systems for hoistway pressurization and mechanical-pressure sandwich
systems, where building ventilating units are used to contain smoke during a fire.
Although many codes continue to require specific means to address elevator hoistway
venting, the overall design for smoke control in the building should be considered
in design of elevator hoistways. Consideration for building occupants who
may be threatened by fire requires designers to view the structure in a holistic
fashion, where all systems can be integrated to maximize life-safety opportunities.
The proposed design should be reviewed by the architect, mechanical engineer, and
fire protection engineer to ensure that the finished result achieves goals set for the
building’s life-safety capabilities. The importance of proper elevator hoistway design
in high-rise buildings cannot be overemphasized.
16.7.3 Machine Rooms
Construction of enclosures of spaces containing machines, control equipment, and
sheaves should be equivalent to that used for the hoistway enclosure. To dissipate
machinery heat and to preserve computerized elevator control equipment, the spaces
must be air conditioned.
Due to the dangers involved in elevator machinery, nonelevator equipment is not
permitted in elevator machine rooms. If the driving machine is located at the top
of the hoistway, other machinery and equipment for building operation may also
be installed in the machine room but must be separated from the elevator equipment