Civil Engineering Reference
In-Depth Information
FIGURE 4.21
Another example of pounding damage and even-
tual collapse caused by the Izmit earthquake in Turkey on August
17, 1999. (
Photograph from the Izmit Collection, EERC, University
of California, Berkeley.
)
building, the two segments that make up the building are usually much more stiff in their
long directions, then across the segments. Thus damage tends to occur where the two segments
of the T join together.
4.6
RESONANCE OF THE STRUCTURE
Resonance
is defined as a condition in which the period of vibration of the earthquake-
induced ground shaking is equal to the natural period of vibration of the building. When
resonance occurs, the shaking response of the building is enhanced, and the amplitude of
vibration of the building rapidly increases. Tall buildings, bridges, and other large struc-
tures respond most to ground shaking that has a high period of vibration, and small struc-
tures respond most to low-period shaking. For example, a rule of thumb is that the period
of vibration is about equal to 0.1 times the number of stories in a building. Thus a 10-story
