tw = Thickness of link beam web, in. (mm)
iii. For beams in partially restrained
moment frames, EIb in Equation 6-7 is modified to:
Aw = Area of link beam web, in2 (mm2)
1
EIb (adjusted) =
(6-9)
e = Length of link beam, in. (mm)
6h
1
+
l2 K Θ EIb
b
Ke =
Stiffness of link beam, kip/in
K s Kb
where:
(kN/mm) =
K s + Kb
h = Average story height of the columns,
Ks = Shear stiffness of link beam, kip/in
in. (mm) K2 = Rotational spring stiffness, estimated
GAw
as MCE/0.005, kip-in per rad (MCE/0.044, kN-m per
(kN/mm) =
e
rad.).
G = Shear modulus, kips/in2 (kPa)
MCE = Expected moment capacity of the
connection, kip-in. (kN-m)
Kb = Flexural stiffness of link beam, kips/in
(kN/mm) = 12EIb/e3.
iv. For link beams in eccentric braced
frames:
2. Concrete moment frames. Acceptance
criteria for reinforced concrete beams, columns, and
2 y = QCE/eKe
(6-10)
beam/column joints in moment frames are tabulated
in Chapter 7. The numerical values are given as the
where:
plastic rotation angles in radians as defined in Figure
6-2. As described in Paragraph 6-3b(2)(b)1 above,
2 y = Yield deformation of the link, rad.
the total chord rotation may be assumed to be equal
to the interstory drift ratio, ) /h, and the yield chord
QCE =
Expected shear strength of link
rotation, 2 y, for beams and columns is assumed to
beam, kips (kN) = 0.6 Fye Aw
be:
Fye = Expected yield strength, ksi (kPa)
M CE d
2y=
(6-11)
Ec I g
Aw = Area of link beam (db-2tf)tw, in2 (mm2)
where:
db = Depth of link beam, in (mm).
tf = Thickness of link beam flanges, in.
(mm).
6 - 11
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