Ground Motions and Structures - Earthquake Engineering for Structural Design - page 354

354 Earthquake Engineering for Structural Design

(a) (b)
Figure 8.52 Panel types: (a) Slender unstiffened panel; (b) Compact stiffened panels
(De Matteis et al, 2006)

contribution to the structural behavior of buildings. If a suitable connecting system is
adopted, such panels may, in fact, provide a remarkable increasing of both lateral
stiffness and energy dissipative capacity of the structure as a whole (De Matteis,
1998). The second solution, which is alternative to concentric bracings with limited
capacity to dissipate seismic energy, consists of introducing in the structure some
panels made of low yield steel or aluminium (De Matteis et al, 2006). These panels are
intended as a primary system in absorbing the lateral seismic actions, while the beams
and columns have only the role of carrying out the gravity loads.
The classification of shear panels is based on the dissipation mechanism. In case of
slender unstiffened panels, the shear panel dissipates energy by means of the tension
field action, due to the fact that elastic buckling occurs in the compression field (Fig.
8.52a). For compact stiffened panels, the buckling phenomena are delayed and the
dissipative mechanism corresponds to pure shear (Fig. 8.52b). Obviously, the shear
buckling in elastic field occurring in slender unstiffened panels produces a poor
dissipation during the cycle behavior. Therefore, the pure shear dissipative mechanism,
offered by compact stiffened panels, is preferable because it allows a stable inelastic
cyclic behavior and a uniform material yielding spread over the entire panel. The low
yield stress ensures an amount of energy dissipation starting from small deformation
levels as in case of moderate earthquakes, working as damper also during the
serviceability limit state.