Page 304 - Handbook of Structural Steel Connection Design and Details

Partially Restrained Connections

Partially Restrained Connections 289

Figure 4.9 Typical CW-BB connection (Astaneh-Asl,
1995).

(CB-BB), is essentially the same as that shown in Fig. 4.5 for a T-stub
connection. The main differences are that the springs representing
the tension elongation of the bolts and the yielding in the flange have
to be replaced by a spring that represents the behavior of the weld
between the column flange and the beam flange.
Table 4.1 lists the main failure modes for this type of connection. In
general the desired failure mechanisms will be slip of the bolts fol-
lowed by yielding of the beam and the connection plate. The main
failure modes to avoid are brittle failure of the welds, shear failure of
the bolts, and a net section failure in the connecting plate or beam.
With this hierarchy established, it is possible to develop a design
strategy, as outlined in the steps shown below, for the design of these
connections under monotonic loads.
The design of any connection subjected to seismic loads is similar
in principle to the static design, except that a capacity-design
approach must be followed. In this context, capacity design implies
that the connection must be designed to behave in a ductile manner
under the maximum expected forces that can be introduced by the
framing members. Thus, for CW-BB connections, the welds need to
be strong and tough enough such that the weld strength does not
control and fracture problems related to the welding procedures
and materials are eliminated. For CW-BB connections, yielding
should be limited to the connection plate or the beam flange. This
requires a careful assessment of the minimum and maximum
capacities associated with each of the springs in Fig. 4.4, since the

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