Civil Engineering Reference
In-Depth Information
Figure B.16
Collapse of precast RC building during the 1999 Kocaeli (Turkey) earthquake: general damage (
top
)
and close-up of the details (
bottom
)
frequently in city centres, where due to the high price of land, buildings are constructed close to each
other. Figure B.17 provides some examples of pounding in RC buildings of similar and different
heights. Major damage is frequently found in adjacent structures of different heights; taller buildings
are, in fact, more fl exible than their lower counterparts.
Pounding may also occur in suspended elements connecting adjacent structures. Figure B.18 shows
the extensive damage localized at the connection of the suspended walkway in the California State
University building during the 1994 Northridge earthquake. Separation joints with an adequate gap
may be used to prevent damage caused by pounding of adjacent buildings or connecting elements,
as occurred in the cases shown in Figures B.17 and B.18 .
• Inadequate seismic detailing is perhaps the most common cause of structural damage in RC structures.
Lack of stirrups, insuffi cient concrete confi nement, insuffi cient concrete cover, use of smooth longi-
tudinal steel bars and insuffi cient anchorage lengths are frequently observed during post- earthquake
surveys. Many failure modes are generated by a combination of the above factors. Figure B.19 illus-
trates the collapse of a multi-storey RC frame with inadequate seismic detailing in the columns during
the 1999 Athens earthquake.
Another common failure mode caused by inadequate detailing is the punching shear, which occurs
especially in fl at slabs. Several examples of this brittle failure mode were observed, for example,
during the 1971 San Fernando, the 1989 Loma Prieta and 1994 Northridge earthquakes, in California
(Elnashai
et al
., 1989). High concentrated loads (combined shear and moment) in columns may lead
to the perforation of fl oor diaphragms. This damage can be prevented by locating close-spaced stir-
rups horizontally around beam-to-column joints. In some cases, punching shear may also occur at
the column base.
