Page 308 - Forensic Structural Engineering Handbook

DEFECTS, DETERIORATION, AND DURABILITY 9.19

Danger. The qualitative combination of hazard and risk that yields an unreasonable expo-
sure of a person to harm.
Deficient. Lacking some desirable element or characteristic. Deficient is used generally to
describe the condition of a component that has defects or deterioration.
Defect. The nonconformity of a component with a standard or specified characteristic.
Defect is used sometimes as a synonym for “failure,” but the preferred meaning is to indi-
cate only a deviation from some (perceived) standard which may, but will not necessarily,
result in a failure.
Degradation. The lowering of a material’s characteristics (such as strength or integrity).
Similar to deterioration, but not necessarily time-dependent.
Degradation factor. A group of external factors that adversely affect the performance of
building components and materials, including weathering, biological, stress, incompatibil-
ity and use factors. 3
Design life. The period of time after installation during which all properties of a compo-
nent or system are intended or expected to exceed the minimum acceptable values when
properly maintained.
Deterioration. The gradual adverse loss of physical or chemical properties of a material.
Distress. The collective physical manifestations of a failure as perceivable problems, such
as cracks, spalls, corrosion, or staining.
Durability. A qualitative measurement of design life (expectation of how long a compo-
nent or system should last); also, the relationship of its actual performance (service life)
compared to its design life.
Failure. An unacceptable difference between expected and observed performance; also,
the termination of the ability of a component or system to perform an intended or required
function. Not all failures are catastrophic; most involve components which do not perform
as expected.
Failure mechanism. An identifiable phenomenon which describes the process or defect
by which a component or system suffers a particular type of failure.
Failure mode. A description of the general type of failure experienced by a system. A
broader term than “failure mechanism,” encompassing fundamental behavior such as shear
and tension.
Flaw. A relatively small imperfection in a material or component. Note, however, that
even small flaws can cause catastrophes if they occur in critical areas.
Hazard. An attribute of a component or system that presents an inherent threat of harm to
a person, without regard to risk exposure. See also “danger.”
Incompatibility factor. A degradation factor resulting from detrimental chemical and
physical interactions between materials and components.
Latent defect. A concealed defect which causes or has the potential to cause a failure after
a relatively long period of time during which it was dormant or nonmanifest.
Maintainable. A material or component that may last with proper treatment on a sched-
uled or condition-based cycle for the service life of the building or structure.
Patent defect. A defect which is readily open to observation—something that is evident
and obvious.
Permanent. Material or component with a design life equal to that of the building or structure.
Premature failure. Failure of a material, component or system prior to the end of its
design life.