Building Design and Construction Handbook - Merritt - Ventech!

7.110 SECTION SEVEN
and usually independent of the shear connection needed to support the beam reaction.
Framed, seated, and end-plate connections (Arts. 7.35.1 to 7.35.5) are examples
of shear connections. Those in Fig. 7.17 (p. 7.32), are moment connections.
In Fig. 7.17a to g, flange stresses are developed independently of the shear connections,
whereas in h and i, the forces are combined and the entire connection
resolved as a unit.
Moment connections may be classified according to their design function: those
resisting moment due to lateral forces on the structure, and those needed to develop
continuity, with or without resistance to lateral forces.
The connections generally are designed for the computed bending moment,
which often is less than the beam’s capacity to resist moment. A maximum connection
is obtained, however, when the beam flange is developed for its maximum
allowable stress.
The ability of a connection to resist moment depends on the elastic behavior of
the parts. For example, the light lug angle shown connected to the top flange of
the beam in Fig. 7.52b is not designed for moment and accordingly affords negligible
resistance to rotation. In contrast, full rigidity is expected of the direct welded
flange-to-column connection in Fig. 7.52a. The degree of fixity, therefore, is an
important factor in design of moment connections.
Fixity of End Connections. Specifications recognize three types of end connections:
simple, rigid, and semirigid. The type designated simple (unrestrained) is
intended to support beams and girders for shear only and leave the ends free to
FIGURE 7.52 Methods of constructing flexible welded connections.