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6
Damage and Losses to
Special Facilities and Urban Systems
The methods used to estimate losses for the general population
of buildings must be modified for application to lifelines, facilities
with essential emergency functions, or facilities with a potential for
very large losses.
[II?E:LI~ES
T~ifelmes (or utilities and infrastructure systems) include railroad,
airport, motor vehicle, water, telephone, electricity, natural gas or
oil pipelines, sewage, port and airport, and communications services.
The words systems and services are central to the distinction between
the loss estimation process for lifelines as compared to buildings.
Service outages are almost always a prominent concern addressed
by lifeline loss studies. Property losses are also important, but casu-
alties associated with damage to lifelines usually are small. A lifeline,
such as a water or electrical utility's facilities and functions, must be
analyzed as a system rather than as separate, unrelated structures.
Securing the active cooperation and support of local lifeline own-
ers, operators, and regulators is the key to producing a satisfactory
loss estimate. An understanding of how the system operates is es-
sential.
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The first step in the analysis of lifelines is to estimate the prom
ability that components of the system will fail. Examples of com-
ponents would be bridges in highway routes, switchyards and trans-
former stations in power systems, and pumping stations in water and
sewage systems. The estimation of Tosses to the individual compo-
nents of a system has a less extensive historical Toss experience to
support the development of construction class motion-damage rela-
tionships than with buildings. The most ambitious attempt to date
to develop classes that include nonbuilding structures is ATC-13, in
which some 30 classes are related to lifelines.
The pane! believes that the DPMs in ATC-13 provide the best
available guidance, especially for bridges, although adjustments for
local conditions will generally be necessary. ATC-13 DPMs should
be used with a knowledge of the specific definitions of the classes.
For example, a DPM that was devised for the case of seismically
anchored electrical equipment should not be applied to a case where
the equipment is unanchored.
Buried pipelines are more vulnerable to collateral hazards such as
fault ruptures, landslides, and liquefaction than they are to ground
shaking. The probability of failure of such a pipeline under these
collateral hazards will depend on the detailed characteristics of the
ground movement and the material, age, depth of burial, and wall
thickness and diameter of the pipeline. There are examples of suc-
cessful pipeline performance as well as failures for each of these
collateral hazards. For any specific pipeline and detailed character-
istic of ground movement, an evaluation of pipeline performance can
be made. However, such detailed evaluations are beyond the feasible
scope for a large geographic loss estimation study that includes many
such pipelines. For these studies, the probability of failure of buried
pipelines should be treated as being rather high (greater than 50
percent) wherever collateral hazards are postulated to occur.
Similarly, with the exception of bridges, which are potentially
vulnerable to both effects, highway and railway networks are also
more vulnerable to collateral hazards than they are to ground shak-
ing. The probability of failure of links in such networks due to col-
lateral hazards should be treated similarly to that described above
for buried pipelines.
Once the probability of individual components failing has been
estimated, the next step is then to evaluate the influence of the failure
of components or segments on the performance of the system, as a
whole. If analytical models exist for the system (utilities will often
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as
have such models), the effect on overall performance of the loss of
some components can be estunated readily. Lacking any available
system-wide models, expert opinion based on available data must be
used to estimate the outages that might be expected. In either case,
the result is a scenario describing the state of the lifeline; that is, its
ability to provide service following the earthquake.
In addition to degradation in system-wide performance, there
may be localized outages. For example, pipes in local distribution
systems may fad! as a result of ground shaking or ground failures, and
streets may become clogged by debris. These local failures contribute
to the overall problem of restoring service.
The time needed to restore service is an important factor in
planning for disaster response. This is, in part, a matter of the
time required to bring components back to a serviceable condition
(e.g., to fix breaks in pipelines or to inspect bridges). The ATC-13
report contains time-to-restore-service matrices for a number of life-
line components. Restoring service also depends on the emergency
response capability of the lifeline operator or of other emergency
response agencies. A utility with an earthquake-resistant radio sys-
tem, personnel who undergo annual earthquake exercises to test their
ability to carry out preassigned tasks, and back-up plans for using
emergency bypasses should be much more able to contain the impact
of earthquake damage than another utility that does not have these
capabilities and experiences the same damage. Considerations such
as these must be handled on a case-by-case basis after evaluation of
the utilities' emergency preparedness.
Loss estimation studies have seldom incorporated lifelines into
the study to the same extent as building losses. Lifeline Toss esti-
mation methods are not as mature as for building loss estimation,
and the problems are very complex. There has been considerable re-
search into methods for evaluating the performance of interconnected
systems in probabilistic terms, but as yet these sophisticated meth-
ods have not been used in conventional, multipurpose, regional-scale
loss studies. The pane! encourages more systematic and sophisti-
cated studies of losses to lifeline systems, partially for the purpose
of aiding in the maturing of lifeline loss estimation. However, ad-
ditional damage statistics will accumulate only slowly, because so
many factors affect the behavior of components in lifeline systems.
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FACIIITIES WITH ESSENTIAL EMERGENCY FUNCTIONS
In general-purpose loss estimates, the main focus of this study,
special attention must be given to those facilities most essential
to emergency response, such as fire stations, emergency operations
centers, and hospitals. The key question is: How well will these
facilities be able to perform after an earthquake?
Obviously, if such facilities suffer severe structural damage, their
usefulness wiB be negated or greatly impaired. However, even if there
is little or no structural damage, the facility may be unable to func-
tion effectively if nonstructural damage causes critical equipment
to be dislodged or overturned, or if essential or dangerous chem~-
cals have been thrown down from shelves, or if lifelines services are
interrupted.
Nonstructural damage is significant because it is generally more
widespread than structural damage. Even a moderate level of ground
shaking (such as V! or VIT on the MM! scale) can cause nonstruc-
tural damage, such as overturned gas cylinders or water heaters and
the release of flammable or toxic gas. The inventory task of field
surveying nonstructural characteristics for the building population
at large has yet to be attempted in a large-scale study, but this effort
should be undertaken for the smaller number of essential, emergency
function facilities that are within the scope of a large-scale study.
During a loss study, it generally is necessary to walk through each
essential facility allowing sufficient time to assess the likelihood of
severe structural damage, but it also is essential to ascertain whether
critical equipment and supplies have been adequately secured, and
whether back-up resources have been arranged to deal with util-
ity outages. This is labor intensive work and requires earthquake
engineering expertise, but these are unavoidable costs.
Undertaking a detailed structural analysis of such facilities is
generally beyond the scope of a loss study. However, it may be desir-
able to examine structural drawings and to utilize a rapid assessment
method. Critical evaluation of these methods is beyond the scope of
this report.
Even though each emergency facility is inventoried, the problem
of potential liability to those involved with this work may make it
desirable for a number of such facilities to be grouped when stating
expected losses. That is to say, the result is a scenario describing the
functionality of the emergency response system as a whole and not
the functionality of individual facilities.
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57
... ~ ... ~ .. .. ~ _
_
_
_ .~. -
______ - ~ ~
- : _:: - _ _
The flexible, first-story of this hospital building was overstressed during the 1971
San Fernando earthquake (M 6.63. Although designed in accordance with the
1970 building code, this reinforced-concrete structure was so severely damaged
that it was torn down. The intensity of ground shaking was much greater than
the hypothetical intensity upon which the code requirements were based. Photo
courtesy of P. C. Jcnnir~g~.
Aerial view of collapsed hospital buildings in Sylmar, California. The older,
weaker buildings collapsed and the newer, stronger buildings survived with only
minor damage during the 1971 San Fernando earthquake (M 6.63. Photo courtesy
of G. Hou~r~cr.
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58
The ATC-13 report solicited from experts the DPM for mean
percentage property loss (termed damage factor by ATC-13 and gen-
erally called damage ratio by others) versus the MMI for six classes
of equipment (i.e., residential, office, electrical, mechanical, high
technology and laboratory, and vehicles). The validity of these rela-
tively gross groupings is unknown and untested at present, although
considerable variability is known within these types of equipment.
For example, in the mechanical category, many pumps are routinely
bolted to concrete slabs and are relatively earthquake resistant, even
where earthquakes are not specifically considered in design. Also
within this overall category of mechanical equipment is air-handling
equipment mounted on springs, and these items are usually quite
vulnerable to earthquakes except where special seismic measures are
taken. The six classes of equipment analyzed by ATC-13 are also not
all-inclusive.
The equipment DPMs were not directly used in the ATC-13
functional loss estimation process. Instead, experts were asked to
assign recovery times to the damage states of Table ~2 (e.g., loss
damage state 1 = no damage) for 60 socioeconorn~c classes of build-
ing use. For the class defined as health care services, for example,
each expert had to decide how a given damage state (that now in-
cluded structural plus equipment damage in its definition) affected
the facility's functionality in terms of time to restore service to 30
percent, 60 percent, and 100 percent. I,oss of function resulting from
lifeline service outages were included as a separate step. To be valid,
these relationships (of MMI to equipment damage, and of combined
structural and equipment damage state to functional Toss) must be
defined more specifically than to say they represent "typical" Cali-
fornia practice.
It should be clearly recognized that there is less certainty and
less maturity in such techniques for estimating functional loss than
for estimating property loss. For essential facilities, individual field
visits rather than reliance on general relationships are recommended.
Considerable potential exists for improving estimates of the per-
formance of essential facilities through research into the earthquake
performance of nonstructural items and identification of typical non-
structural conditions in different parts of the country. While the
state of the art of quantitative nonstructural loss estimation is not
well developed, guidance for identifying and reducing nonstructural
vuInerabilities is available in works such as those by McGavin (1981,
1986), Reitherman (1985, 1986), Stratta (1987), and the Veterans
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s9
Administration (1976, 1981). For emergency planning purposes,
references documenting functional Tosses (e.g., Arnold and Durkin
t1983] concerning hospitals) or other reports in the postearthquake
reconnaissance and research literature are useful for pointing the
way toward improving emergency response capabilities, even though
quantitative response dysfunction can only be very approximately
predicted.
FACILITIES WITH A POTENTIAL FOR LARGE LOSS
~ this category are large and densely occupied buildings and
other facilities such as tank farms, refineries, dams, liquefied natural
gas (I,NG) plants or storage areas, chemical plants, nuclear plants,
and pipelines containing hazardous materials. The characteristic
feature of these facilities is that failure could cause an enormous
number of casualties as well as very large property losses.
Except possibly for large and densely occupied buildings, there
may be only a few of these facilities in a given study area. Thus, the
loss estimator cannot take advantage of averaging out uncertainty
in performance over many facilities, as can be done for the ordinary
building stock. Unless the loss attributable to a facility can be stated
with great confidence, including it may completely bias the projected
overall losses for the region. Since the Toss from an individual building
or other facility cannot be estimated reliably except through very
detailed and expensive analysis, it follows that possible losses from
such facilities should not be quantitatively included in the overall
estimated loss.
Obviously, however, the existence of such potentially hazardous
facilities cannot be ignored. They should be highlighted in the inven-
tory, and the cognizant regulatory bodies should be urged to require
that detailed studies be made. A large-scale multipurpose study can
educate local officials and stab personnel about the potential threat
and the need to map the location of such facilities.
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60
Damage to a liquid storage tank during the 1971 San Fernando earthquake
(M 6.6~. The sloshing of the druid contents overstressed the wall of the tank.
Sometimes such overstressed tanks collapse and combustible contents ignite.
Photo cowtc~11 of P. C. Jcnrung~.
Representative terms from entire chapter:
collateral hazards
