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Distribution of Earthquake Input Energy in Structures.

Distribution of Earthquake Input Energy in Structures.
(2968 K)

Khashaee, P.; Mohraz, B.; Sadek, F.; Lew, H. S.; Gross,
J. L.

NISTIR 6903; 80 p. January 2003.

### Available from:

: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.

Telephone:
1-800-553-6847 or 703-605-6000;

Fax: 703-605-6900; Rush
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Order number: PB2003-102247

### Keywords:

earthquakes; structures; design spectra; earthquake
energy; earthquake engineering; structural engineering

### Abstract:

*
In developing an energy-based design approach and
assessing the damage potential of structures, one must
know the distribution of earthquake input energy among
energy components: kinetic, elastic strain, hysteretic,
and damping. This report examines the influences of the
ground motion characteristics: intensity, frequency
content, and duration of strong motion and the
structural properties: ductility, damping, and
hysteretic behavior on the distribution of input energy
for a one- and a five-story building using 20
accelerograms, ten with short and ten with long duration
of strong motion. Results indicate that for certain
damping ratios, ductility has a significant influence on
input energy and its distribution among energy
components in a structure. For a given ductility ratio,
small damping ratio (less than 5%) has a minor effect on
input energy, but a major influence on the energy
distribution. Damping ratios larger than 5% have a
significant influence on the input energy and its
distribution. Three energy ratios that relate to
hysteretic energy were computed: the maximum ratio of
hysteretic to input energy, the ratio of the maximum
hysteretic energy to the maximum input energy and the
equivalent number of yield excursions. It is found that
(Eh/Eir)m generally reflects the energy demand for the
entire duration of accelerogram. The study shows that
(Eh/Eir)m is independent of the duration of strong
motion and period of structure; however, Ehm/Eirm is
independent of both only for periods less then 1 s.
Results indicate that as the duration becomes longer the
equivalent number of yield excursions Neq increases
indicating more structural damage. The influence of
ground motion characteristics and structural properties
on the distribution of energy parameters for a
five-story building with fixed-base, base-isolation,
supplemental damping and semi-active control are
examined using the 20 accelerograms. The results show
that: 1) the distribution of energy through the height
of the building is mostly independent of the frequency
content and the duration of strong motion, 2)
base-isolation, supplemental damping, and semi-active
control reduce the damage potential by reducing the
input and hysteretic energy demands and have significant
influences on the distribution of energy through the
height of the building.
*