Civil Engineering Reference
In-Depth Information
final collapsed condition of the building consists of one floor stacked on top of another,
much like a stack of pancakes.
Pancaking of reinforced concrete multistory buildings was common throughout the
earthquake-stricken region of Turkey due to the Izmit earthquake on August 17, 1999.
Examples of pancaking caused by this earthquake are shown in Figs. 4.14 to 4.16.
Concerning the damage caused by the Izmit earthquake, Bruneau (1999) states:
Pancaking is attributed to the presence of “soft” lower stories and insufficiently reinforced
connections at the column-beam joints. Most of these buildings had a “soft” story—a story with
most of its space unenclosed—and a shallow foundation and offered little or no lateral resis-
tance to ground shaking. As many as 115,000 of these buildings—some engineered, some
not—were unable to withstand the strong ground shaking and were either badly damaged or
collapsed outright, entombing sleeping occupants beneath the rubble. Partial collapses
involved the first two stories. The sobering fact is that Turkey still has an existing inventory of
several hundred thousand of these highly vulnerable buildings. Some will need to undergo
major seismic retrofits; others will be demolished.
Another example of pancaking is shown in Fig. 4.17. The site is located in Mexico City,
and the damage was caused by the Michoacan earthquake in Mexico on September 19,
1985. Note in Fig. 4.17 that there was pancaking of only the upper several floors of the
parking garage. The restaurant building that abutted the parking garage provided additional
lateral support, which enabled the lower three floors of the parking garage to resist the
earthquake shaking. The upper floors of the parking garage did not have this additional lat-
eral support and thus experienced pancaking during the earthquake.
FIGURE 4.14
Pancaking of a building during the Izmit earthquake in Turkey on August 17, 1999.
(
Photograph by Mehmet Celebi, USGS.
)
