Ground Motions and Structures - Earthquake Engineering for Structural Design - page 344

344 Earthquake Engineering for Structural Design

(a) (b)

Figure 8.41 Welded connection types: (a) Fully welded; (b) Welded and bolted
connections (Gioncu et al, 2000)

.
specific sections of beam, the reduced beam section protects the node from plastic
deformations, producing a ductility enhancement. At local level, the inelastic
deformations in the beam do not involve the connection welds (Fig. 8.42b) and the
stress demand at the beam-to-column connection is reduced. As a consequence,
strength requirements for column flange, continuity plates and panel zone are less
stringent than for traditional beam-to-column connections. Moreover, the cross section
reduction is applied to the beam flange width, hence the b/t flange slenderness ratio
reduces and the local instability phenomena are delayed. At global level, the ductility
benefits from the increased rotational capacity; moreover “dog-bones” encourage the
attainment of more dissipative collapse mechanisms, being the capacity design for
members easier to be achieved. But, due to the large plastic deformations, the reduced
sections are much damaged and its repair may be expected to be very difficult or even
impossible. Therefore, it seems to be very rational to use a dismountable element for
the zone of reduced section (Fig. 8.42c) (Balut and Gioncu, 2003).