Advances in Seismic Design Methodologies - Earthquake Engineering for Structural Design - page 441

Advances in Seismic Design Methodologies 441

9.6 BEHAVIOR OF NON-STRUCTURAL COMPONENTS DURING
EARTHQUAKES

9.6.1 Importance of Non-structural Components

Non-structural components are, by definition, not intended to resist any seismic forces
than those resulting from their mass. They are also, in the main, elements which are not
designed by structural engineers, but architects and mechanical or electrical engineers
take primary responsibility for them.
After many years of efforts by researchers and practitioners to develop
performance-based earthquake engineering methodologies, it is now obvious that the
problem of non-structural components is one of the most critical issues of the seismic
design. Unlike structural components, most of the non-structural components are
vulnerable to a relatively low level of earthquake. According to reconnaissance reports
on the earthquakes of 1989 Loma Prieta and 1994 Northridge, the economic loss due to
non-structural components generally exceeds the one due to structural elements (Lee et
al, 2006). In the case of the 1995 Kobe earthquake, the cost of non-structural
components damage equalizes the cost of structural damage. Poor performance of non-
structural components is the main contributor to damage, losses and business
interruption for the majority of facilities after an earthquake. This subject received
special attention after the 1971 San Fernando earthquake, when it became clear that the
damage to non-structural components can not only result in major economic loss (79%
from damage costs was due to non-structural components), but also can pose a real
threat to life safety. For example, an evaluation of damage to hospitals following this
earthquake revealed that many facilities still structurally intact were no longer
functional, because of loss of essential equipment and supplies.
The value of non-structural components is, generally, expressed as a percentage of
the total cost of a building, depending on the type of the building considered. In a
storage building with few mechanical services and non-structural elements, non-
structural elements can be 20 to 30% of the total investment. For industrial buildings,
with important production equipments, this percentage increases until 40 to 50%. In
complex civil buildings, the cost of non-structural components increases drastically.
The average incidence on the total investment of non-structural components in case of
offices, hotels and hospitals is given in the following table as a percentage of the total
investment (Whittaker and Soong, 2003):

Office Hotel Hospital

Structural 18% 13% 8%

Non-structural 62% 70% 48%

Contents 20% 17% 44%