New Challenges in Seismic Design - Earthquake Engineering for Structural Design - page 20

- Examination of the influence of local soil conditions as a function of
stratification and dynamic properties of soil layers.
The determination of the structural response must be setup by considering
some specific aspects of seismic design:
- Soil-foundation-structure-non-structural elements interaction, considering
the actual properties of each element and the modification of these
properties in function of the earthquake level.
- Spatiality of response, considering the horizontal and vertical components
of seismic actions.
- Effects of structural and accidental torsions, produced by the structural
asymmetry and incoherency of seismic actions.
- Influence of horizontal and vertical irregularities on the overall structural
response.
- Pounding of two neighboring buildings when the seismic separation is not
sufficient.
The need of developing some specific design methodologies comes out from the
following requirements:
- Improvement of the equivalent lateral force analysis, by proposing a set of
response spectra as a function of ground motion characteristics. Different
spectra for near-field, far-field, interplate, intraplate earthquakes are
required.
- Improvement of the static elastic-plastic incremental pushover analysis, by
the determination of a proper loading distribution along the structure
height taking into account the vibration mode influence.
- Development of the incremental methodology for time-history analysis, in
order to evaluate the collapse condition of structures. Considering that the
natural period of severe earthquakes is longer than the one for moderate
earthquakes, the methodology must consider the contemporary
modification of accelerations and natural periods.
1.6ISSUES FOR SEISMICDESIGN
1.6.1DesignTeam
The main purpose of this topic is to filter the complex information obtained from
Engineering Seismology and Earthquake Engineering, by using the engineering
judgments.
A design earthquake related to a design action, which ensures to the structure
an adequate seismic safety, is proposed instead of a realistic earthquake. The
definition of such a design earthquake requires a series of engineering judgments
on seismological and structural matters, together with a close collaboration among
seismologists, geotechnists and structural engineers. The philosophy of engineering
seismic design states that the design should accomplish the objectives of multi-
level approaches (different behaviors for minor, moderate or severe earthquakes),
and the seismic design requiring the corresponding design loads. All these issues