Civil Engineering Reference
In-Depth Information
members are used.
∗
Built-up open compression members are often fabricated with
lacing bars and stay (tie or batten) plates or perforated cover plates.
6.3.3.1
Buckling Strength of Built-up Compression Members
Only bending deformations were considered in the development of Equation 6.24
for buckling strength,
P
cr
. The effect of shear forces was neglected. For solid
section compression members, this is appropriate. However, for built-up compression
members, the shear force may create deformations of the open section that reduce the
overall stiffness and, thereby, reduce the buckling strength. Therefore, the curvature
of the compression member due
to
shear must be included in Equation 6.14 to deter-
mine the critical buckling load,
P
cr
, for built-up compression members. The shear
force is (
Figure 6.12)
P
d
y(x)
d
x
V(x)
=
P
sin
ϕ
(x)
=
(6.40)
γ
v
, given as
with curvature,
d
2
y(x)
d
x
2
β
A
g
G
eff
d
V(x)
d
x
=
β
P
A
g
G
eff
γ
v
=
,
(6.41)
P
x
ϕ
(
x
)
V
(
x
)
M
(
x
)
P
y
FIGURE 6.12
Bending and shear forces at compression member cross section.
∗
This is generally the case for railway compression members exposed to rain, ice, and snow.
