Ground Motions and Structures - Earthquake Engineering for Structural Design - page 367

Ground Motions and Structures 367

cost for the required function after an earthquake (Adams, 2004).
The traditional design philosophy of seismic-resistant structures is based upon the
dissipation of the earthquake input energy by means of plastic excursions, leading to
structural damage which has to be controlled in order to prevent failure. The ability of a
structure to withstand severe earthquakes is strictly related to the capacity of uniformly
distributing the structural damage. In the classical design approach, the damage
concentrations can lead to failure modes which are characterized by a reduced
dissipation capacity (Mazzolani and Piluso, 1996). Therefore, one of the most critical
decisions influencing the ability to withstand earthquakes is the choice of the basic
structural configuration.
Building structures belong to many types and configurations and, of course, a
universal ideal configuration for any particular type of building does not exist.
However, there are some basic principles for seismic-resistant design which can be used
as guidelines in selecting an adequate building configuration. These basic guidelines are
the following (NISEE, 1997):
- Building (structure and non-structural elements) should be light and avoid
unnecessary masses.
- Building and structure should be simple, symmetric and regular in plan and
elevation, avoiding large height-width ratio and large plan area.
- Building and structure should have a uniform and continuous distribution of
mass, stiffness, strength and ductility, avoiding formation of soft stories.
- Structure should have relatively shorter spans than non-seismic-resistant
structure and avoid use of long cantilevers.
- Structure should be designed to have good details and erected respecting
construction quality.
- Non-structural components should either be well separated so that they will not
interact with the structure, or they should be integrated with the structure. In the
last case, the structure should have sufficient lateral stiffness to avoid damage to
these non-structural elements under minor or moderate earthquakes.
- In case of integrated non-structural elements, they should be distributed in the
structure in such a way to avoid the introduction of any disturbance in the
uniformity of structural stiffness.
- Structure should be detailed so that inelastic deformations are controlled to
develop in selected regions, according to a desirable hierarchy. The structure
must have a stable energy dissipating post-yield behavior.
- Structure should possess enough redundancy and robustness to have the largest
possible number of defense lines, so the inelastic behavior of the whole structure
finds its way to avoid the structure collapse.
- In case of neighboring building existence, the separation between the buildings
must assure pounding is prevented.

- Structure should be provided with a balance of stiffness, strength, ductility and

robustness among its elements, connections and supports.