Knauf Seismic Design

Types of Collapse and Damage
The collapse of buildings can either be
global or local. The term local implies that
only a part of the load-bearing structure or
a single construction component collapses.
When a collapse is termed global, the
whole structure is considered to have been
destroyed.
Cracks, plastic displacements etc. are
damages which can cause the loss of a
building’s usability, as well.
Apart from basic “under dimensioning,”
the following types of collapses may occur
due to errors in either the conception or
execution of buildings:
The “soft story effect” (fi gures 2 and 3)
occurs due to a story with little rigidity (for
architectural reasons mostly the ground
fl oor) that attracts stresses from rigid stories
and subsequently collapses. It is the
weakest part of the structure. Strictly speaking,
it is a local collapse, but it can cause
a global collapse and lead to the ultimate
loss of the building.
The “short columns effect” (fi gure
7) is caused by undesired load swaps into
construction components that are not divided
well enough from the load-bearing
structure. The reason is the subsequent increase
of rigidity through masonry and the
following higher seismic load due to the
shortening of the swing period.
The sudden and unannounced collapse
of infill masonry (fi gures 6 and 8) is extremely
dangerous to people in the building.
It can even lead to a complete collapse
of the whole building (fi gure 5). The reason
is the higher rigidity of infi ll masonry,
as compared with the softer columns, that
causes the swapping of loads into the masonry.
The brittle material collapses in an
explosion-like manner.
6
Figure 6: Collapse of infi ll masonry
Figure 7: Short columns effect
Figure 8: Collapsed infi ll masonry