Estimating Losses from Future Earthquakes (1989) / Chapter Skim
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4. Building Damage and Losses
4. Building Damage and Losses
Pages 26-44
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From page 26... ...
The age of a building is sometimes used as an indirect indicator of seismic design level in areas where seismic codes have been adopted, and it can indicate typical construction practice in a given region. In the planning stages for a study, the steps of selecting a classification system, developing methods to prepare the inventory, and assembling motion-damage information are all interdependent.
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From page 27... ...
Structures that have adequate strength to resist moderate shaking may not be able to withstand strong ground shaking. Photo courtesy of G
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From page 28... ...
For loss studies elsewhere in the United States, these basic schemes should be reviewed and possibly modified and simplified to take into account local construction variations and problems of assembling an adequate inventory. For example, in the study of six cities in the Midwestern United States (Allen and Hoshall et al., 1985)
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From page 29... ...
Reinforced concrete, precast reinforced concrete, lift elate Reinforced concrete, floors and roofs not concrete Mixed construction, small buildings and dwellings Mixed construction, superior damage control features Mixed construction, ordinary damage control features Mixed construction, intermediate damage control features Mixed construction, unreinforced masonry Buildings specifically designed to be earthquake resistant 4D 4E 5A 5B 5C ED 5E 6 SOURCE: Algermissen and Steinbrugge (1984~. since in principle it is possible to develop a perfect inventory, but in practice compromises must always be made.
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From page 30... ...
As discussed in the section on user needs, it should be possible to disaggregate losses to any local political unit, which in the case of a large city may mean wards, precincts, or districts. Census tracts or postal zip codes also are convenient minimum geographical units, but if used they may require localized modifications to make the tract or zip code data correspond to other boundary lines.
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From page 31... ...
There appears to be only a weak correlation between socioeconomic characteristics, such as number Of employees and the Standard Industrial Classification number indicating economic sector, and construction characteristics relevant to earthquake loss estunation. While a convenient data file, such socioeconomic information is not particularly relevant to the task of producing an inventory of facilities according to construction classes.
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From page 32... ...
in connection with largescale earthquake loss estimation rather than for the field survey of individual essential emergency operation facilities and life support systems, which was the initial purpose for devising this multihazard survey method. Field sampling of buildings previously surveyed by
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From page 33... ...
should be evaluated in the context of loss estimation. MOTION-DAMAGE RELATIONSHIPS Identifying the relationship between the intensity of ground shaking and the damage experienced by a group of generally similar structures, or a construction class, is essential to vulnerability analyses.
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From page 34... ...
34 Splh-level houses that were deAclent in earthquake resistance collapsed durlog the 1971 San Fernando, C~ll~rnla earthquake (~ 6.6~. ~lLbulk houses in the area supplied, experlenclug only cracks in plater.
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From page 35... ...
~ 20 a) CL cn CO o 10 5 / _ / BE // ~.3/~: / 3C 4A DB / i// ~ '-''ZU-A- — V Vl Vll Vll IX MM INTENSITY FIGURE 4-2 Loss ratio versus Modified Mercalli Intensity (mean damage ratio curves)
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From page 36... ...
from none to total, is divided into damage states, each of which is described both by words and by a range of damage ratios. For each intensity of ground shaking, numbers in a column give the fractions of buildings experiencing different damage states; the numbers in each column sum to unity.
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From page 37... ...
Evaluating Motion-Damage Relationships The loss ratio curves in Figure ~2 were constructed, employing considerable judgment, using loss data gathered during various earthquakes, principally those occurring in California and a few other western states, along with data from foreign earthquakes where construction has been compatible. Actual data of this type are most complete for wood-frame dwellings (these data do not appear in Figure 4-2)
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From page 38... ...
1 1 1 1 Cot Cot .
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From page 39... ...
In all such future studies, the distribution of damage should be documented not just the mean loss ratios, and not just by documenting interesting or dramatic individual failures in a reconnaissance overview. There has been an effort to develop and use empirical relations connecting damage directly to magnitude and distance from an earthquake (Steinbrugge et al., 1984~.
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From page 40... ...
x (number of buildings) x MERE, all building categories where MART is the loss ratio (or mean damage ratio)
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From page 41... ...
The early NOAA-USGS studies generally used historical rates of casualties per unit of populaton for wood-frame dwellings and estimated rates for other types of construction, or used city-wide casualty rates from previous earthquakes applied to the population as a whole, adjusted up or down based on changes in construction practice. These estimates were In effect crude extrapolations of the limited data available, primarily from California earthquakes.
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From page 42... ...
For light steel construction and wood-frame construction, multiply all numerators by 0.1. SOURCE: Applied Technology Council (1985~.
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From page 43... ...
These obviously are both matters for which far more data from actual earthquakes are required to advance the state of the art.
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From page 44... ...
Destruction can be seen of the Trans-Ecuadorian oil pipeline (indicated by arrows) and adjacent highway by a debris flow issuing from a minor tributary of the Coca River.
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