Engineering and Construction

Pancaking occurs when the earthquake shaking causes a soft story to collapse, leading to total failure of the overlying floors. These floors crush and compress together such that the 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 Kocaeli earthquake on August 17, 1999. Concerning the damage caused by the Kocaeli 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 unen-closed—and a shallow foundation and offered little or no lateral resistance 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 under- go major seismic retrofits; others will be demolished.

An example of pancaking caused by the Kocaeli earthquake is shown in Fig. 14.6.