Civil Engineering Reference
In-Depth Information
(1994)
A large proportion of the most severe damage to buildings in the January 17, 1994,
Northridge earthquake in Southern California was experienced by condominium
buildings. Several thousand of these structures were situated in the most severely
shaken areas, and the largest single incidence of fatalities - 16 individuals - occurred
in one such building, the Northridge Meadows Apartments.
The typical configuration of these buildings provides street level “tuck under”
parking, either of timber framed carport configuration or comprising a reinforced con-
crete structural slab supported on perimeter walls and internal columns, above which
is constructed two or three levels of stucco clad, timber framed, residential units.
A consistent pattern of seismic weaknesses was observed. These include
overloading of the perimeter walls, incipient punching shear damage of column/slab
connections, in-plane shear failures of stucco and drywall clad walls, cracking of
vertical timber studs, splitting of bottom sill plates, shattering of lightweight concrete
floor slabs, out-of-plane separation of stucco, and many connection detail deficiencies
(Figure 5-20).
A particularly interesting aspect of the behavior of the condominium buildings
in the Northridge earthquake is that many clearly experienced a seismic load demand
that closely approximated the available capacity. Consequently the response observa-
tions provided an invaluable data base with which to assess the effectiveness of the
design and construction practices that were followed.
In the case of the Northridge Meadows Apartments, the collapse of several
blocks can be ascribed directly to the soft bottom story, as a consequence of
insufficient shear resistance being provided at this level.
Lesson Learned
The style of multi-story, multi-family residential buildings typified by the Northridge
Meadows Apartments proved hazardous in the moderate to strong earthquake shaking
experienced on January 17, 1994. The frailties of the structural form were exposed.
Stricter code provisions and more stringent inspection procedures to ensure improved
quality control of the construction process will reduce the possibility of an event like
this from happening in the future.
References
"Preliminary Report of the Seismological and Engineering Aspects of the January 17,
1992, Northridge Earthquake," (1994). Report UCB/EERC 94/01, Earthquake
Engineering Research Center, University of California at Berkeley.
Hall, John. F. ed. (1994).
Northridge Earthquake, January 17, 1994; Preliminary
Reconnaissance Report
, Earthquake Engineering Research Institute, Oakland,
California.
