Civil Engineering Reference
In-Depth Information
TABLE 6.5
Critical Buckling Coefficients
Steel Yield Stress (
F
y
)
(ksi)
Critical Buckling Coefficient (
C
c
)
36
143
44
129
50
121
6.3.1.3
Yielding of Compression Members
When
F
all
=
0.55
F
y
, the slenderness ratio,
KL/r
, from Equation 6.33 is
0.629
E
KL
r
≤
F
y
.
(6.36)
Compression members are very short and without potential for instability for slen-
derness below that given by Equation 6.36. The value of Equation 6.36 for various
steel yield strengths is given in
Table 6.6.
Therefore, the allowable compressive force,
C
all
, based on yielding is
C
all
=
0.55
F
y
A
g
.
(6.37)
6.3.1.4
Compression Member Design in Steel Railway Superstructures
Equations 6.35 (used with either 6.21 or 6.33) and 6.37 encompass the AREMA
(2008) recommendations for allowable compressive stress considering elastic stabil-
ity, inelastic stability, and compressive yielding, respectively. Equation 6.34 provides
Fa AREMA
Fa CRC
Fa Euler CRC
Fa Euler AREMA
50,000
40,000
30,000
20,000
10,000
0
0
20
40
60
80
100
120
140
160
180
200
-10,000
kL
/
r
FIGURE 6.10
CRC parabolic and AREMA linear compression member curves.
