Civil Engineering Reference
In-Depth Information
For tubular members satisfying out-of-roundness tolerances, as presented in
Chapter 5
, F
h
should be determined from:
F
h
=
F
y
for F
he
>
2
:
44F
y
(3.47)
0
:
4
F
y
≤
F
h
=
0
:
7
ð
F
he
/F
y
Þ
F
y
for
0
:
55F
y
<
F
he
≤
2
:
44F
y
(3.48)
F
h
=
F
he
for F
he
≤
0
:
55F
y
(3.49)
where F
y
is the representative yield strength, in stress units, and F
he
is the elastic
hoop buckling strength, in stress units.
The elastic hoop buckling strength (F
he
) is determined from:
F
he
=
2C
h
Et/D
(3.50)
where the critical elastic hoop buckling coefficient C
h
is:
C
h
=
0
:
44t/D for
μ ≥
1
:
6D/t
3
/
4
C
h
=
0
:
44t/D
+
0
:
21
ð
D/t
Þ
μ
for 0
:
825D/t
≤ μ <
1
:
6D/t
C
h
=
:
737/
ðμ −
:
579
Þ
:
≤ μ <
:
0
0
for 1
5
0
825D/t
C
h
=
0
:
80 for
μ <
1
:
5
where
μ
is a geometric parameter,
r
2D
t
L
r
D
μ =
(3.51)
and where L
r
is the length of tubular between stiffening rings, diaphragms or
end connections.
For members that violate the allowable tolerance and have out-of-roundness
greater then 1% and less than 3%, the reduced value of F
he
will be:
r
D
max
−
0
D
min
F
'
he
=
F
he
1
−
0
:
2
:
8
(3.52)
0
:
01D
n
where D
max
and D
min
are the maximum and minimum values of any measured
outside diameter at a cross-section and D
n
is the nominal diameter.
The unity check U
c
of a member under external pressure should be calcu-
lated from:
pD/2t
F
h
/
U
c
=
(3.53)
γ
R,h
Tubular Members Subjected to Combined Forces without
Hydrostatic Pressure
Members subjected to combined forces, which give rise to global and local
interactions between axial forces and bending moments, without hydrostatic
pressure, have different requirements. Generally, the secondary moments
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