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 MIL-HDBK-1013/1A
A third upgrade suggestion is to use steel sheets or plates to
achieve the degree of ballistic hardening required, as determined by the
selected ballistic threat (Table 45). Some results of tests on upgraded
walls using mild steel are shown in Table 49. Other types of steel such as
high-hardness, dual-hardness, or rolled-homogeneous steel plates, also could
be used.
Table 49
Upgraded Walls for High-Severity Threat
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* Wall
*
*
Upgrade
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* Hollow 8-inch (200-mm) concrete block
*
1/8-inch (3-mm) steel(a) *
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*
*
* 4-inch (100-mm) face brick
3/8-inch (9.5-mm) steel
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* 2-inch (50-mm) concrete T-beam
*
*
3/8-inch (9.5-mm) steel
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(a) Mild steel per QQ-S-741D.
Although steel armor can be used either on the inside or outside of
walls, its use on the inside of a wall appears more appealing because: (1)
the armor prevents spalling of the original wall material; (2) it occupies
little interior space; (3) it can be cut and fitted at the site; (4) it can
be installed with only hand and power tools, or in some cases, with only
thermal tools; (5) when installed in a location protected from the weather,
it requires very little maintenance; (6) no noticeably hardened areas can be
seen by outsiders; and (7) ornate exteriors are not affected by the upgrade.
Some disadvantages include: (1) critical cutouts for pipes, vents,
receptacles, doors, windows, and switches must be made in the steel; (2)
walls and footers may not be strong enough to support the additional load;
and (3) daily operations may be affected by the armor installation.
When deciding what type of upgrade options can be applied to
existing walls, consideration should be given to the availability of
materials and installation hardware, labor requirements (skilled or
unskilled), aesthetic appearance, degree of interference with daily
operations, structural loads, installation time, and cost. Because of
variation in threat definitions, every structure has unique ballistic
hardening requirements, but a compromise usually can be made to satisfy both
the functional and the protective elements of buildings. Table 50 provides
additional examples of retrofit construction.
Doors. Eliminating all unnecessary doors is the first step in
6.5.3.2
upgrading existing facilities. Steel pedestrian doors mounted in stamped
steel frames frequently are found in existing facilities. While these doors
provide little ballistic resistance, they can be upgraded. Steel sheets,
described in the previous paragraph, can be used to upgrade these doors.
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