j.
Steel Stud Shear Walls.
whether the frame is in a building-frame system, a
moment-resisting frame system, or a dual system.
(1) Description of system. Steel studs may be
(3)
Redundancy.
A sufficient number of
used in lieu of wood studs in structural bearing walls.
braced frames should be provided so that a failure of
To function as shear walls, steel-stud walls need
a single member or connection will not result in
bracing. In principle, plywood sheathing could be
instability of the entire lateral-force-resisting system.
used, but there are no available allowable shear
values.
Instead, it is customary to use diagonal
(4) Braced frame types. The principal types
braces made of steel straps welded to the face of the
of braced frame are the familiar concentric braced
steel studs. Sheathing such as plywood or gypsum
frame (CBF), the relatively new eccentric braced
board may be used to serve architectural purposes
frame (EBF), and the knee-braced frame (KBF).
such as containing insulation and backing up finishes.
(5) Design criteria. The criteria governing the
(2)
Design Criteria.
The Department of
design of structural steel and wood vertical braced
Defense is currently reviewing tests performed by
frames will be as prescribed in this chapter.
industry with the objective of providing approved
Reinforced concrete braced frames are not permitted
design criteria for steel stud framing systems.
A
in buildings governed by this document.
moratorium currently precludes the use of this system
as a lateral-force-resisting system. It is anticipated
(a) Structural steel braced frames. Structural
that applicable criteria will be available prior to the
steel braced frames will conform to the requirements
final version of this document.
of the AISC "Seismic Provisions for Structural Steel
7-3.
Steel Braced Frames.
Buildings" and the further provisions of this
document.
a.
General.
(b) Wood braced frames. Wood braced
frames will be designed by using normal procedures
(1) Function. Vertical braced frames are used
illustrated in many easily obtainable texts and are not
to transmit lateral forces from the diaphragm above
covered in this manual.
Allowable loads and
to the diaphragm below or to the foundations. They
resistance factors for wood members shall be in
are similar to shear walls in their general function and
accordance with ASCE 16-95.
stiffness is compared with moment-resisting frames.
b.
Concentric Braced Frames.
(2)
Definition of braced frame.
A braced
frame is defined as an essentially vertical truss
(1)
Eccentricities.
Although the frame is
system of the concentric or eccentric type that is
called "concentric," there may be minor eccentricities
provided to resist lateral forces. Note that for braced
frames, as for shear walls, the R value depends on
between member centerlines at the joints, and these
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