Civil Engineering Reference
In-Depth Information
rigorous geotechnical earthquake investigations would be required for critical facilities. For
example, the Federal Emergency Management Agency (1994) states:
Critical facilities are considered parts of a community's infrastructure that must remain
operational after an earthquake, or facilities that pose unacceptable risks to public safety if
severely damaged. Essential facilities are needed during an emergency, such as hospitals, fire
and police stations, emergency operation centers and communication centers. High-risk facil-
ities, if severely damaged, may result in a disaster far beyond the facilities themselves.
Examples include nuclear power plants, dams and flood control structures, freeway inter-
changes and bridges, industrial plants that use or store explosives, toxic materials or petroleum
products. High-occupancy facilities have the potential of resulting in a large number of casu-
alties or crowd control problems. This category includes high-rise buildings, large assembly
facilities, and large multifamily residential complexes. Dependent care facilities house popu-
lations with special evacuation considerations, such as preschools and schools, rehabilitation
centers, prisons, group care homes, and nursing and convalescent homes. Economic facilities
are those facilities that should remain operational to avoid severe economic impacts, such as
banks, archiving and vital record keeping facilities, airports and ports, and large industrial and
commercial centers.
It is essential that critical facilities designed for human occupancy have no structural weak-
nesses that can lead to collapse. The Federal Emergency Management Agency has suggested
the following seismic performance goals for health care facilities:
1.
The damage to the facilities should be limited to what might be reasonably expected after a
destructive earthquake and should be repairable and not life-threatening.
2.
Patients, visitors, and medical, nursing, technical and support staff within and immediately
outside the facility should be protected during an earthquake.
3.
Emergency utility systems in the facility should remain operational after an earthquake.
4.
Occupants should be able to evacuate the facility safely after an earthquake.
5.
Rescue and emergency workers should be able to enter the facility immediately after an
earthquake and should encounter only minimum interference and danger.
6.
The facility should be available for its planned disaster response role after an earthquake.
As previously mentioned, in addition to the type of facility, the scope of the investiga-
tion may be dependent on the requirements of the local building codes or other regulatory
specifications. Prior to initiating a site investigation for seismic hazards, the geotechnical
engineer and engineering geologist should obtain the engineering and geologic require-
ments of the governing review agency. For example,
Guidelines for Evaluating and
Mitigating Seismic Hazards in California
(Division of Mines and Geology 1997) states that
geotechnical engineers and engineering geologists:
May save a great deal of time (and the client's money), and possibly misunderstandings, if
they contact the reviewing geologist or engineer at the initiation of the investigation. Reviewers
typically are familiar with the local geology and sources of information and may be able to pro-
vide additional guidance regarding their agency's expectations and review practices.
Guidelines for geologic or geotechnical reports have been prepared by a number of agencies
and are available to assist reviewers in their evaluation of reports. Distribution of copies of
written policies and guidelines adopted by the agency usually alerts the applicants and consul-
tants about procedures, report formats, and levels of investigative detail that will expedite
review and approval of the project.
The scope of the investigation for geotechnical earthquake engineering is usually
divided into two parts: (1) the screening investigation and (2) the quantitative evaluation of
the seismic hazards (Division of Mines and Geology 1997). These two items are individu-
ally discussed in the next two sections.
