Ground Motions and Structures - Earthquake Engineering for Structural Design - page 333

Ground Motions and Structures 333

frequent causes producing progressive collapse is the earthquake. Among the different
definitions of progressive collapse, there is one which directly refers to the buildings'
robustness (Mazzolani, 2002, Gioncu, 2006, 2007):
“…. design for consequences of localized failure from an undefined cause, a
strategy which ensures that a building is sufficiently robust to sustain a limited extent
of damage, depending on the consequence class, without collapse “.
The most important conceptual aspect for avoiding the structural collapse during
earthquake is to design the structure in such a way to allow the possibility of
redistributing the internal actions when some critical members are damaged. The
Alternative Path approach considers the residual resistance against the progressive
collapse by providing a second modality to transfer the loads when the primary load-
bearing members are eliminated due to local damage (Fig. 8.33a) The very recent
studies on this aspect refer to the improving the catenary effects of the floor slabs in
such a way to prevent progressive collapse in the event of loss of bearing capacity of
columns.This improving is related to the increasing the connection's tension capacity.
In order to obtain this catenary effect, the location of cables in zones susceptible to
column damage is a very efficient solution for reinforced concrete buildings. In case of
steel structures, it is required to increase the joint capacity for tension forces, using (for
instance) the side-plate connections .

Alternative
paths

Missing
columns

(a)

Figure 8.33 (continues)