Pnc =
least equal to the expected nominal axial tension
nominal axial compression
strength of the web member, RyFyAg.
strength of the diagonal members of the special
segment (kips) (kN);
(4)
Non-special
segment
nominal
strength.
All members and connections of
" = angle of diagonal members with
special truss moment frames, except those
the horizontal plane.
members identified as special segments, shall
have a design strength to resist the factored
(5)
Compactness.
Diagonal
web
gravity loads and the lateral loads necessary to
members of the special segment shall be made of
develop the expected vertical nominal shear
flat bars. The width-thickness ratio of such flat
strength in all special segments, Vne, given by the
bars shall not exceed 2.5. The width-thickness
following formula:
ratio of chord members shall not exceed the
limiting λ values from Table B5.1 of the AISC
p
L - L
Design Specification. The width-thickness ratio
3.4Ry M nc
+ 0.07 EI 3 s + Ry (Pnt + 0.3Pnc )sin α
Vne =
L
Ls
s
of angles, and flanges and webs of tee sections
(7-4)
used for chord members in the special segment,
where:
shall not exceed 52/ Fy (137 / F y for F y in
Ry =
defined in the AISC Design
MPa.
Specification;
(6)
Lateral bracing. Top and bottom
Mnc = nominal flexural strength of the
chords of the trusses shall be laterally braced at
chord member of the special segment (kips-in.)
the ends of special segments, and at intervals not
(kN-m);
to exceed Lp, according to Section F1.1 of the
AISC Design Specification, along the entire
EI =
flexural elastic stiffness of the
length of the truss. Each lateral brace at the ends
chord members of the special segment (kip-in2)
of, and within, the special segment shall have a
(MPa);
design strength to resist at least 5 percent of the
L = span length of the truss (in.) (mm);
required compressive axial strength, Pnc, of the
largest adjoining chord member. Lateral braces
Ls = 0.9 times the length of the special
outside of the special segment shall have at least
segment (in.) (mm);
2.5 percent of the required Pnc of the
largest adjoining chord members.
Pnt = nominal axial tension strength of
f.
Acceptance Criteria.
diagonal members of the special segment (kips)
(kN);
(1) Response modification factors, R, for
Performance Objective 1A for moment frames in
7-104
Previous Page
