Civil Engineering Reference
In-Depth Information
6.3.3.1.1 Critical Buckling Strength of Laced Bar Built-up Compression
Members without Batten Plates (Pinned at Each End)
(Figure 6.13a
and b)
Shear is resisted by pin-connected truss behavior of lacing bars (for double lacing,
consider tension resistance only).
1
A
lb
E
eff
sin
Ω =
,
(6.48a)
cos
2
φ
φ
13.2
(L/r)
2
A
g
A
plb
1
1
α =
+ Ω
P
cr
=
1
+
,
(6.48b)
cos
2
sin
φ
φ
where
A
plb
is the cross-sectional area of diagonal lacing bars in each panel of the
member.
For single lacing,
A
plb
=
A
lb
=
t
lb
w
lb
.
2
t
lb
w
lb
.
Here
t
lb
is the thickness of the lacing bar,
w
lb
is th
e wid
th of the lacing bar,
r
is the
radius of gyration of the compression member
For double lacing,
A
plb
=
2
A
lb
=
=
I/A
g
, and
is the angle of the
lacing bar from the line perpendicular to the member axis (should be about 30
◦
for
single lacing and 45
◦
for double lacing).
Φ
6.3.3.1.2 Critical Buckling Strength of Built-up Compression Members
with Batten Plates Only (Pinned at Each End) (Figure 6.13c)
Shear is resisted by flexure of the batten plates and the main member elements.
a
2
24
E
eff
I
ab
12
E
eff
I
bb
+
Ω =
(6.49a)
ϕ
ϕ
a
l
p
c
L
L
p
L
p
b
a
b
c
d
e
f
FIGURE 6.13
Various built-up compression members comprised of lacing bars with and
without batten plates, and perforated cover plates (note that, for clarity, stay plates required at
the ends of laced bar members are only shown at the bottom of compression members a, b, d,
and e).
