Civil Engineering Reference
In-Depth Information
where
I
pc
is the moment of inertia of half the member (one “flange”) about the
member axis at the center of the perforation, and
A
pc
is the area of half the member
(one “flange”).
AREMA also presents other recommendations related to perforated cover plates
for built-up compression member design as
c
≤
2
w
perf
,
(6.70)
b
,
c
≤
l
p
−
(6.71)
where
w
perf
is the width of the perforation,
l
p
is the distance between the centers of
perforations, and
b
is the width of the perforated plate between the inside lines of
fasteners.
The thickness of perforated cover plates should be governed by the largest of the
following expressions relating to local plate stability criteria:
t
pc
≥
b
/
50
(6.72)
w
perf
)
F
y
/E
,
1.17
(b
−
t
pc
≥
(6.73)
0.90
b
F
y
/E
√
F
all
/f
t
pc
≥
(
in.
)
,
(6.74)
where
F
all
/f
4.
Perforated cover plate thickness is also based on transverse shear,
V
, at the
centerline of the cover plate. The minimum perforated cover plate thickness
(Equation 6.13) is
≤
3
Vl
p
t
pc
≥
c)
,
(6.75)
2
τ
all
b(l
p
−
τ
all
is the allowable shear stress (0.35
F
y
recommended by AREMA, 2008).
The gross section through the perforation (with only the perforated area removed) of
the plate is included in the member gross area for compression design.
Example 6.7 outlines the design of a perforated cover plate built-up compression
member.
where
Example 6.7
Design a 19.55 ft long compression member to resist a 550 kip load as a solid,
built-up laced bar, built-up batten plate, and built-up perforated cover plate
member.
Design of the solid section
Compression member: W14
×
90 rolled section
26.5 in.
2
A
=
999 in.
4
I
x
=
