30 September 1999
installations. Some buildings may have different structural systems in each of the two major
orthogonal directions. Separate structural scores should be determined for the structural
system in each orthogonal direction.
(1) Basic score. The NEHRP building type for the building being reviewed is identified
in Lateral Load System Data Sheet (Figure B-1). As a first step in determining the structural
score, the "Basic Score" for the representative building type should be circled and modified by
the applicable structural modifiers in that column. The Basic Score for each building type, as
developed in FEMA 154, was the negative logarithm of the probability of damage exceeding 60
percent of the building replacement cost. The probabilities of damage were obtained from the
ATC-13 data (a probabilistic earthquake damage evaluation study for structures in California
based on expert opinion polls), and the basic scores thus derived were intended to be non-
arbitrary relative vulnerability assessments for each building type. For purposes of this form, the
FEMA 154 basic scores have been reviewed in the light of building damage observed in recent
California earthquakes, as well as applicability to typical DOD buildings, and were revised by
judgment to represent the relative vulnerability.
(2) Two to four stories. Buildings in this height range are in resonance with the
predominant periods (i.e., about 0.2 to 0.4 second) of seismic ground motion in firm soils.
These buildings are therefore expected to be subjected to greater damage.
(3) Poor condition. The structural condition of the building should be carefully noted
during the field visit. This includes loss of section due to corrosion in steel buildings; excessive
cracking of concrete or evidence of staining and spalling due corrosion of reinforcement; fungus
(e.g., damp rot) or borer damage in timber structures; cracking, spalling, or weak mortar in
masonry buildings; or evidence of past alterations that may have damaged or removed
structural members. The indicated modifiers for poor condition should be circled only when the
condition is considered to be worse than would be expected for the average building of that type
and age. Any unusual conditions should be noted at the bottom of the sheet under
(4) Details. This is a subjective assessment of the structural detailing as evidenced in
the structural drawings or as noted in the field. The cumulative modifier varies from +1.0 for
good details to