c) Wall construction. New construction options for walls
include concrete/sand combinations as shown in Figure 69. This figure shows
the concrete wall thickness required versus standoff distance for sand depths
(if used) ranging from 0 to 28 inches (700 mm). An example of the use of
this figure is as follows. If no sand and no predetonation screen are used,
about 44 inches (1.1 m) of concrete are required. If the concrete wall
thickness is limited to 12 inches (300 mm) and no sand is used, the minimum
standoff distance required for the predetonation screen is about 11 feet (3.3
m). If 16 inches (400 mm) of sand is employed, the standoff distance is
reduced to 5 feet (1.5 m). These combinations of depths of sand and concrete
used with an effective predetonation screen have been found adequate to stop
the penetration of the predetonated RPG.
Another wall concept is the 32-inch (810-mm) sandwich ASP Walling
design shown in Figure 70. The ASP Walling system consists of formed metal
sheets joined together to constitute both the permanent formwork, while at
the same time acting as antispalling plates to contain fragments. The basic
component of the ASP Walling system is a wall element consisting of
interlocked external sheets. The two faces are tied to each other by diagonal
lacing panels which, in zig-zag fashion, form a rigid permanent formwork into
which 1.5-inch (40-mm) hard stones are placed (see Figure 70).
Roofs and Floors. Because of the large quantities of material
required to stop an RPG jet, structural considerations will likely preclude
their application to roofs or floors open from above and below. In this
case, critical assets may only be protected from above and below using
sacrificial areas as discussed in par. 220.127.116.11.
Areas to be protected against an RPG attack should be
free of any windows.
4) Doors. Foyers should be provided at protected entrances or
door openings should be offset so that each door is opposite a solid wall
construction associated with a sacrificial area. Examples of possible
configurations are illustrated in Figures 71, 72, and 73. The design of
exterior concrete walls should be of the same construction as other protected
walls. Predetonation screens at the proper standoff can also be provided if
necessary (see Figure 69).
Retrofit Construction. The most cost-effective retrofit concept
involves the use of sand and predetonation screens or walls. Sand bags or
sand-grids used in combination with properly located predetonation screens
can stop an RPG from penetrating into high-security areas constructed of
concrete and certain CMU construction.