New Challenges in Seismic Design - Earthquake Engineering for Structural Design - page 19

Figure 1.6 Design philosophy for earthquake loads: (a) Definition of reduction
factor q ; (b) Good, medium and poor ductility

The Seismic Design introduces additional difficulties with respect to the above
ones. The most important aspect is the request that the structure is able to resist
severe earthquakes with acceptable damage but without collapse, by exploiting its
ductility properties. This modern design philosophy requires special design
methodologies, very different from the conventional ones. This is the basic reason
why Earthquake Engineering can be considered as a new branch of Structural
Engineering, its main tasks being the evaluation of the construction vulnerability
against seismic actions.
A fundamental aspect is the consideration of the earthquake type in the
analysis, which must involve the following problems:
- Development of specific methodologies for interplate and intraplate

earthquake types, by using different ground motions records and response
spectra.

- Identification of the differences between the near-field and far-field

earthquakes, the pulse characteristics for the former being very important
and the number of important cycles for the second.