Page 300 - Handbook of Structural Steel Connection Design and Details

Partially Restrained Connections

Partially Restrained Connections 285

provides the designer with a wide spectrum of possibilities in select-
ing the structural members and their connections. It is disconcerting
because most designers do not have extensive experience with PR
analysis and PR frame behavior.
There are currently numerous good texts that address the analysis
and design of PR frames (Bjorhovde et al., 1988, 1992, 1996; Chen
and Lui, 1991; CTBUH, 1993; Chen and Toma, 1995; Chen et al.,
1995; Leon et al., 1996; Chen, 2000; Faella et al., 2000; Chan and
Chui, 2000). There is a considerable range in the complexity of the
analysis approaches proposed in the literature. The appropriate
degree of sophistication of the analysis depends on the problem at
hand. When incorporating connection restraint into the design, the
designer should take into account the effect of reduced connection
stiffness on the stability of the structure and the effect of connection
deformations on the magnitude of second-order effects (ASCE, 1997).
Usually design for PR construction requires separate analysis to
determine the serviceability limit state and the ultimate limit state
because of the nonlinear nature of the M- curves.

4.3 Design of Bolted PR Connections
The design of a connection must start from a careful assessment of its
intended performance. This requires the designer to determine the
performance criteria with respect to stiffness (FR, PR, or simple),
strength (FS or PS), and ductility. The stiffness is critical with respect
to serviceability, while strength and ductility are critical with respect
to life-safety issues. These criteria must be consistent with the model
assumed for analysis. From Fig. 4.7, if an assumption of a rigid con-
nection was made in the analysis, the resulting connection will typi-
cally be fully welded, welded-bolted, or a stiffened thick end-plate
type. Similarly, if the connection was assumed as simple, then a shear
plate welded to the column and bolted to the beam or angles bolted to
both column and beam are appropriate.
If explicit use of PR behavior was made in the analysis, in the form
of a rotational spring with a given K , then a wide variety of connec-
serv
tions can be chosen, ranging from an end plate (close to FR/FS perfor-
mance) to top-and-seat angles (close to simple performance). The key
here is to match the K of the connection as designed to that
serv
assumed in the analysis. The matching should be done at the service
level because drift and deflection criteria will probably govern the
design in modern steel frames. The stiffness of the connection should
be checked with at least the component model approach (Fig. 4.5).
Since the stiffness of the connection will be dependent on the actual
configuration of the connecting elements and the size of the framing

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