Civil Engineering Reference
In-Depth Information
L 6 × 4 × 1/2
5/8
"
1.99
"
FIGURE E7.2a
L 8 × 4 × ½, typ
5/8
"
3.17
"
FIGURE E7.2b
Local buckling of outstanding compression elements
:
0.43
E
b
bs
t
bs
=
8
0.5
=
4.0
≤
F
y
≤
10.4 OK
Serviceability-deflection criteria
The required gross moment of inertia for a LL
+
I deflection criterion of
L/f
is (see Chapter 5)
Δ
M
LL+I
Lf
7314
(
90
)f
Δ
Δ
in.
4
.
I
≥
≥
≥
340.4
f
Δ
1934
1934
The required section gross moment of inertia for various deflection
criteria,
f
, is shown in Table E7.3.
The section
I
g
=
Δ
223,444 in.
4
provides a deflection that is 2.5% less than
the AREMA (2008) criteria.
TABLE E7.3
Deflection Criteria,
Required Gross Moment
of Inertia,
I
g
(in.
4
)
L
/
Δ
LL+I
500
170,180
640 (AREMA, 2008)
217,832
800
272,290
1000
340,362
