Civil Engineering Reference
In-Depth Information
and the shear stress over the net area of the plate between the centers of perforations,
τ
pc
,is
V
(l
p
−
3
Vl
p
2
bt
pc
(l
p
−
τ
pc
=
c)t
pc
=
c)
,
(6.12)
where
c
is the length of the perforation.
Rearrangement of Equation 6.12 yields
3
Vl
p
t
pc
=
c)
,
(6.13)
2
τ
all
b(l
p
−
where
τ
all
is the allowable shear stress (0.35
F
y
recommended by AREMA, 2008).
The transverse shear force,
V
, is generally small in tension members, and the
perforated cover plate thickness is primarily dependent on requirements for axial
tension and recommended minimum material thickness (see Chapter 5).
The net section through the perforation of the plate is included in the member net
area.
Example 6.5
Use the AREMA (2008) recommendations to select bolted lacing bars and stay
plates for tension member U1-L1 of Example 6.1. The member cross section
is comprised of two C 12
◦
×
30 channels 12 in. apart (Figure E6.4).
Lacing bars:
Minimum width for single flat lacing bars
3.5 in.
Use approximately 60
◦
angle between the lacing bar and the longitudinal
axis of the hanger.
Minimum thickness of the bar
=
=
(
1
/
40
)(
15
/
sin 60
◦
)
=
0.43 in.
For 7/8 in diameter bolts, the minimum bar width
=
3
(
7
/
8
)
=
2.63 in.
Stay plates:
Use at ends and intermediate locations where lacing is not present.
1.5
12"
Lacing bar
or stay plate
12"
Channel
FIGURE E6.4
