Where exterior walls are not designed for the full design
The following terms are to be applied and identified for
loads, special consideration shall be given to construction
each project-specific risk assessment:
types that reduce the potential for injury (see Building
No restriction. No restrictions on the type of glazing.
Materials in this section).
Design for full load:
Limited protection. These windows do not require design
for specific blast pressure loads. Rather, the designer is
Design the exterior walls to resist the actual pressures
encouraged to use glazing materials and designs that
and impulses acting on the exterior wall surfaces from the
minimize the potential risks.
threats defined for the facility (see also discussions in
Design for limited load above).
Preferred systems include: thermally tempered heat
strengthened or annealed glass with a security film
Forced Entry:
installed on the interior surface and attached to the
frame; laminated thermally tempered, laminated heat
Security of Swinging Door Assemblies ASTM F 476 Grade
strengthened, or laminated annealed glass; and blast
____ (project-specific information to be provided).
curtains.
Measurement of Forced Entry Resistance of Horizontal
Acceptable systems include thermally tempered glass;
Sliding Door Assemblies ASTM F 842 Grade ___ (project-
and thermally tempered, heat strengthened or annealed
specific information to be provided).
glass with film installed on the interior surface (edge to
A medium protection level (per TM 5-853) for walls would
edge, wet glazed, or daylight installations are acceptable).
be the equivalent of 4" concrete with #5 reinforcing steel
Unacceptable systems include untreated monolithic
at 6" interval each way or 8" CMU with #4 reinforcing
annealed or heat strengthened glass; and wire glass.
steel at 8 in. interval. TM 5-853 provides other alternatives
for low, medium, and high protection.
The minimum thickness of film that should be considered
is 4 mil. In a blast environment, glazing can induce loads
Exterior Windows
three or more times that of conventional loads onto the
frames. This must be considered with the application of
The multidisciplinary team shall evaluate the perfor-
anti-shatter security film.
mance requirements for all security-glazing materials
proposed for the project. The multidisciplinary team
The designer should design the window frames so that
shall ensure that normal tools carried by firefighters, such
they do not fail prior to the glazing under lateral load.
as a pick head axe, halligan tool, or similar device, can
Likewise, the anchorage should be stronger than the
readily overcome the subject glazing barriers. If the use
window frame, and the supporting wall should be
of more specialized tools, such as a rabbit tool, a k-tool,
stronger than the anchorage.
circular saws, rams, or similar devices is necessary to
The design strength of a window frame and associated
break through the glazing barrier or if the glazing itself
anchorage is related to the breaking strength of the
is hardened that a blast may not blow out the windows,
glazing. Thermally tempered glass is roughly four times as
alternative methods or systems must be designed to
strong as annealed, and heat strengthened glass is roughly
ensure smoke from the incident is not trapped inside
twice as strong as annealed.
the building. (See section on New Construction, Fire
Protection Engineering, Smoke Removal Systems).
244 F A C I L I T I E S S T A N D A R D S
FOR THE
PUBLIC
BUILDINGS
SERVICE
8.4 New Construction
Revised March 2005 PBS-P100
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