Civil Engineering Reference
In-Depth Information
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Poor soil conditions consisting of thick deposits of soft or liquefiable soil that settled
during the earthquake. Because of the inadequate foundations, the wood-frame structures
were unable to accommodate the settlement.
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Inertia loads from heavy roofs that exceeded the lateral earthquake load-resisting capac-
ity of the supporting walls. The heavy roofs were created by using thick mud or heavy
tile and were used to resist the winds from typhoons. However, when the heavy roofs col-
lapsed during the earthquake, they crushed the underlying structure.
4.5 POUNDING DAMAGE
Pounding damage can occur when two buildings are constructed close to each other and, as
they rock back-and-forth during the earthquake, they collide into each other. Even when
two buildings having dissimilar construction materials or different heights are constructed
adjacent to each other, it does not necessarily mean that they will be subjected to pounding
damage. For example, as shown in Fig. 4.17, the restaurant that was constructed adjacent
to the parking garage actually provided lateral support to the garage and prevented the three
lower levels from collapsing.
In the common situation for pounding damage, a much taller building, which has a
higher period and larger amplitude of vibration, is constructed against a squat and short
building that has a lower period and smaller amplitude of vibration. Thus during the earth-
quake, the buildings will vibrate at different frequencies and amplitudes, and they can col-
lide with each other. The effects of pounding can be especially severe if the floors of one
building impact the other building at different elevations, so that, for example, the floor of
one building hits a supporting column of an adjacent building.
Figure 4.20 shows an example of pounding damage to the Anchorage-Westward Hotel
caused by the Prince William Sound earthquake in Alaska on March 27, 1964. Although
not evident in the photograph, the structure shown on the right half of the photograph is a
14-story hotel. The structure visible on the left half of Fig. 4.20 is the hotel ballroom. The
pounding damage occurred at the junction of the 14-story hotel and the short and squat ball-
room. Note in Fig. 4.20 that the main cracking emanates from the upper left corner of the
street-level doorway. The doorway is a structural weak point, which has been exploited
during the side-to-side shaking during the earthquake.
Another example of pounding damage and eventual collapse is shown in Fig. 4.21. The
buildings were damaged during the Izmit earthquake in Turkey on August 17, 1999. As
shown in Fig. 4.21, the pounding damage was accompanied by the collapse of the two
buildings into each other.
It is very difficult to model the pounding effects of two structures and hence design
structures to resist such damage. As a practical matter, the best design approach to prevent
pounding damage is to provide sufficient space between the structures to avoid the prob-
lem. If two buildings must be constructed adjacent to each other, then one design feature
should be to have the floors of both buildings at the same elevations, so that the floor of one
building does not hit a supporting column of an adjacent building.
4.5.1
Impact Damage from Collapse of Adjacent Structures
Similar to pounding damage, the collapse of a building can affect adjacent structures. For
example, Fig. 4.22 shows a building that has lost a corner column due to the collapse of an
adjacent building during the Izmit Earthquake in Turkey on August 17, 1999. The build-
ings were under construction at the time of the earthquake. Note that the roof of the col-
lapsed building now rests on the third story corner of the standing building.
