For nuclear storage areas, the personnel entry gate complex, to
include access and exit routes, will be designed in accordance with NAVFAC P-
272, Definitive Drawings, drawing number 1404126.
Vehicle Gates. Either wheel-supported or cantilever sliding gates
are the best selection for vehicle security gates followed by overhead sliding
gates. Swing gates are a third alternative and lastly, by far the least
desirable, are overhead ("guillotine") gates. Initially, the designer should
begin by evaluating the wheel-supported or cantilever sliding gate. An
initial step in the design is to determine the operational requirements for
the gate. Determine the daily peak and normal work flow of vehicles.
Ascertain the operational access control requirements for the secured area,
i.e., badging, penetrator threat, magnetic sensor personnel monitoring,
package surveillance, type (size) of vehicles to use the gate, etc. These
details will lead to determining the type and size of gates, desirability or
requirement for automatic openers, special hardening requirements, etc. In
areas known for snow or ice buildup, internal heating should be considered in
the gate design.
Sliding Gates. Sliding gates, when open, store parallel to the
adjacent fence line, unlike the large sweeping arc that swing gates require.
When designing the roadbed at the gate opening, the surface should be kept as
straight as possible, allowing for drainage by a slight incline to one side or
the other of the entire roadbed. When an existing road surface is encountered
that is not essentially flat, the designer should require asphalt or concrete
fill to level the roadbed where the gate will be installed.
The cantilever gate design, (Figures 14 and 15), provides full
support and suspension of the gate frame by four rollers secured to two posts
inside the restricted area. Since the required length of a cantilever gate is
1-1/2 times the size of the opening, there must be a straight, and essentially
level, fence line adjacent to the gate to accommodate this length when the
gate is fully open. Cantilever gates can compensate for a somewhat crowned or
unlevel roadbed and do not require a "V"-bar guide rail or trough across the
roadbed. Cantilever sliding gates are not recommended for openings exceeding
24 feet (7.3 m), although two biparting sliding cantilever gates can be used
for openings up to 48 feet (14.6 m).
Wheel-supported gates (Figure 16) for security fences require
either a guide rail ("V"-groove) or trough across the roadbed. With the "V"-
groove design, the gate's leading edge utilizes a wheel that has a deep groove
cut into its outside circumference. This wheel travels on inverted angle iron
that is secured across the roadbed on the ground. The rear of the gate
travels with two wheels riding in "C" channels as shown in Figure 16. The
trough design utilizes a metal wheel with a convex diameter that rides down in
a groove extending across the roadbed. While the trough provides a smoother
surface for vehicular traffic, it is not recommended due to typical debris
buildup in the groove causing the wheel to ride up out of the groove onto the
roadbed surface. In both styles, the upper portion of the gate is supported