Civil Engineering Reference
In-Depth Information
The outstanding legs of angles in the simple beam framing connection (often
referred to as clip angles) must deform sufficiently to allow for flexible connection
behavior. An approximate solution for the maximum thickness of angle to allow
sufficient deformation in a welded beam framing connection, over the depth,
d
, can
be developed assuming the shear force,
P
, is applied at a distance,
e
(see
Figures 9.6
and 9.7). The bending stress,
f
wa
, in the leg of the angle connected to the end plate
(e.g., a beam, girder, or column web plate) from a load,
P
, applied at an eccentricity,
e
, is (from Equation 9.5)
M
S
=
3
Pe
t
a
d
2
,
f
wa
=
(9.10)
where
P
is the shear force applied at eccentricity,
e
,
t
a
is the thickness of angle, and
d
is the depth of the connected angle.
The tensile force,
T
P
, on the connection angle (pulling the angle away from the
end plate connection) is
6
Pe
d
2
.
T
P
=
f
wa
(
2
)t
a
=
(9.11a)
This tensile force,
T
P
, creates a bending moment in the angle legs (assuming the legs
behave as simply supported beams of length 2
l
)of
T
P
(
2
l)
4
M
wa
=
(9.11b)
and the stress in the angle leg is
6
M
wa
t
2
3
T
P
l
t
2
18
Pel
t
2
d
2
.
f
wa
=
=
=
(9.12)
The deformation of the connection angles is
T
P
(
2
l)
3
48
EI
=
2
T
P
l
3
Et
3
f
wa
l
2
1.5
Et
.
Δ =
=
(9.13)
Example 9.3 illustrates the design of a welded beam framing connection.
Example 9.3
Design the welded simple beam framing connection shown in
Figure E9.3
for
a shear force of
P
52 kips. The uniformly loaded beam is 20 ft long, has a
strong axis moment of inertia of 1200 in.
4
and frames into the web of a plate
girder. The allowable shear stress on the fillet welds is 17.5 ksi. Electrodes are
E70XX. The return weld in Section X-X will have a minimum length of twice
the weld size and may be neglected in the design.
P
=
=
1.25
(
52
)
=
65 kips (AREMA recommendation for flexible connection
design)
