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One of the most critical decisions influencing the ability of a
superstructure to withstand earthquake ground shaking is the choice of its
basic plan shape and configuration. The importance of a proper
selection of the superstructure configuration will be discussed and
illustrated for the case of building structures.
Building structures may be of many types
and configurations and there is, of course, no universal ideal
configuration for any particular type of building. However, there
are certain basic or guiding principles of seismic-resistant design
that can be used as guidelines in selecting an adequate building
configuration structural layout, structural system, structural material
and the non-structural components. These basic guidelines are as
follows:
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1.
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Building
(superstructure and non-structural components) should be light
and avoid unnecessary masses.
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2.
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Building and its superstructure
should be simple,
symmetric, and regular in plan and elevation to prevent
significant torsional forces, avoiding large height-width ratio and
large plan area.
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3.
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Building and its superstructure
should have a uniform
and continuous distribution of mass, stiffness, strength and
ductility, avoiding formation of soft stories.
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4.
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Superstructure should have relatively
shorter spans than non-seismic-resistant structure and avoid use of
long cantilevers.
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5.
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The non-structural
components should either be well separated so that they will not
interact with the rest of the structure, or they should be
integrated with the structure. On the latter case, it is
desirable that the structure should have sufficient lateral
stiffness to avoid significant damage under minor and moderate
earthquake shaking, and toughness with stable hysteric behavior
(that is, stability of strength, stiffness and deformability) under
the repeated reversal of deformations which could be induced by
severe earthquake ground motion. The stiffer the structure,
the less sensitive it will be to the effects of
the interacting non-structural components, and the tougher it is,
the less sensitive it will be to effect of sudden failure of the
interacting non-structural elements.
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6.
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Superstructure should be detailed so
that the inelastic deformations can be constrained (controlled) to
develop in desired regions and according to a desirable hierarchy.
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7.
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Superstructure should have the
largest possible number of defense
lines, that is, it should be composed of different tough
structural subsystems which interact or are interconnected by very
tough structural elements (structural fuses)
whose inelastic behavior would permit the whole structure to find
its way out from a critical stage of dynamic response.
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8.
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Superstructure should be provided
with balanced
stiffness and strength between its members, connections and
supports.
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9.
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The stiffness and strength of the
entire building should be compatible with the stiffness and strength
of the soil foundation.
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Copyright 1997, The
Regents of the University of California.
Structural Engineering Slide Library, W. G. Godden, Editor
Set J: Earthquake Engineering, V. V. Bertero
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