fragments. Compatibility with the glazing materials is an
important consideration when selecting sealant material.
Attack Resistance. Each attack tactic imposes unique
requirements on a framing system. These requirements are
described in the following paragraphs for frames subjected to
forced entry, ballistic, and bomb attacks.
Forced Entry Resistance. Forced entry attacks require
a frame to provide delay time against a physical attack. Frame
systems must be designed to resist direct attacks that attempt to
defeat glazing bite, frame material, type, or placement of
Ballistic Resistance. Ballistic attacks represent a
localized threat that can take advantage of frame material or
thickness and clearances at the frame to glazing or frame-to-wall
substrate interfaces. Ballistic resistance is typically obtained
through the use of steel components. Most aluminum frames will
not provide ballistic integrity unless they incorporate steel
inserts in vulnerable areas.
Glazing systems that feature communication or
transaction operations (e.g., teller windows) complicate
ballistic resistant design. Vulnerable communication operations
can be avoided by using electronic systems Vulnerable
transaction operations can be minimized by using deal trays.
For full protection, a ballistic resistant frame must
protect the 1 inch (25 mm) zone near the glazing edge that is not
Blast Resistance. Blast resistant window framing must
fully develop the design strength of a glazing. This requirement
translates to rigid frames and frame-to-wall interfaces and
flatness of the frame and glazing assembly. If the frame system
is skewed or out of plane, the glazing can develop unbalanced
stresses when loaded. This condition will lead to premature
Aluminum frames with steel subframes can be used for
small blast loads. Above 5 psi (35 kPa), frames must be
constructed from steel members.
Environmental Effects. Frames are subjected to
degradation from cleaning materials, cathodic reaction, and water
infiltration. Degradation can be avoided by using compatible
cleaning materials, using compatible spacers and wall substrate