Design of Connections for Steel Members - Design of Modern Steel Railway Bridges - page 401

the technical literature on connection design (e.g., Faella et al., 2000; Leon, 1999). A
flexible end connection will deform and resist very little bending moment. Therefore,
simple beam framing connections that exhibit the characteristics of a flexible con-
nection (see Figure 9.8) may be designed for shear force, P , only ( M e =

0).AREMA
(2008) recognizes that all connections actually exhibit some degree of semirigid
behavior, but allows flexible connection design (with a bolt configuration that allows
for adequate deformation and flexibility) provided the design shear force is increased
by25%.Otherwise,asemirigidconnectiondesignconsideringbothbeamendmoment
and shear is required.
Therefore,flexibleboltedbeamframingconnectionsmustbedesignedconsidering
shear on the outstanding legs of the connection and, due to the eccentricity of the shear
force, combined shear and torsion on the leg of the connection angles fastened to the
web of the beam. However, for flexible bolted connections, ∗ it is usual practice to
disregard the moment, Pe , due to the eccentricity, e .
The angles in the simple beam framing connection (often referred to as clip angles)
must deform in order to allow an appropriate level of flexible connection behavior.
Bolted connections are made more flexible by providing a minimum gage distance,
g , over a distance, h g , from the top of the beam (see Figure 9.21a). AREMA (2008)
recommends h g ≥ h/ 3 and

Lt a
8 ,

g ≥ (9.60)

where L is the length of the beam span in inches and t a is the thickness of angle
in inches.
Equation 9.60 is based on analytical and experimental work regarding the fatigue
strength of typical stringer to floorbeam connections (Yen et al., 1991).
If the beam flanges are coped at the connection, the design must also consider
block shear (the combination of shear or tension yielding on one plane and tension
or shear fracture on the other that may cause tear-out of the shaded area shown in
Figure 9.21b) . AREMA (2008) recommends determination of allowable block shear
strength using Equations 9.48 and either Equations 9.49a or 9.49b, depending on
whether the net fracture strength in tension is greater or less than the net fracture
strength in shear.
Examples 9.6 and 9.7 illustrate bolted beam end framing connection design
assuming no beam end moment (flexible connection) and with a beam end moment
(semirigid or rigid), † respectively.

Example 9.6

Design the bolted simple beam framing connection using 6 × 4 × 1 / 2 in.

angles as shown in Figure E9.5 f or a shear force of P = 80 kips. The beam

∗ In contrast to more rigid welded beam end connections where the moment, Pe , due to eccentricity, e ,
should be considered in the design.
† The beam end moments are generally determined by relatively sophisticated structural analyses that, for
example, consider flexural members with equivalent rotational springs at supports.