Civil Engineering Reference
In-Depth Information
Angle members connected by only one leg are particularly susceptible to shear
lag. AREMA (2008) recommends shear lag reduction factors,
U
c
, between 0.60 and
0.80, depending on the number of bolts per fastener line in the connection.
∗
For members that are continuous through a joint (such as truss chord members
continuous across several panels) or connections where load transfer between the
chord segments is efficient, AREMA (2008) indicates that shear lag may not be of
concern and
U
c
may be effectively taken as 1.00. However, in these circumstances,
engineering judgment may indicate that consideration of
A
e
=
0.90
A
n
is appropriate
for design (Bowles, 1980).
The calculation of effective net area is shown in Example 6.2.
Example 6.2
Member U1-L1 is connected to the bottom chord of the truss in
Figure E6.1
with 7/8 in. diameter ASTM A325 bolts in gusset plates, as shown in
Figures E6.3a
and b. Determine the effective net area for strength design of
the member if it is comprised ofaW12
×
79 rolled section.
A
12.08"
B
T/2
T
4.5"
D
E
C
FIGURE E6.3a
T/2
T
1.59"
T/2
4@ 4"
=
1'
-
4"
FIGURE E6.3b
∗
The larger value of 0.80 is used for angles when there are four or more bolts per fastener line in the
connection (i.e., a relatively long connection).
