Challenges for the Next Generation of Seismic Codes - Earthquake Engineering for Structural Design - page 467

in seismic design development, follow the obtained results, with the intention to
incorporate them in the national codes. After a period in which these results were
adopted without restrictions, the researchers were fully aware of the great
difference between Californian and Japanese fault types and other earthquake
sources, for which the seismic actions are very different and therefore, the
characteristics of sources must be considered in the design provisions. The best
example is the evolution the European codes. The strike-slip faults, with the same
characteristics of the USA earthquakes, which produce high damaging, in the
Mediterranean area exist only in the Northern Anatolia. With the exception of the
Vrancea (Romania) seismic zone, which is a very special case among the European
sources, the faults are characterized by collision, rift and graben systems, very
different from the characteristics of the USA and Japanese last earthquakes. So, the
American and Asian experiences cannot be assimilated in Europe without a very
careful analysis. Therefore, the Eurocode 8 provisions differ from the American
codes in a great extent.
There are some general lessons, which must be learnt from the last world
important earthquakes as well as from the development of research works. There
were some spectacular progresses during the last half century in understanding the
physical phenomena concerning earthquake generation and propagation. At the
same time, the complex and powerful mathematical models and computational
resources to evaluate the structural response were developed.
Unfortunately, there is an insufficient impact of these advances on the practical
design applications (Esteva, 2005). There are some general lessons, that must be
learnt from the last important developments in seismic design, which are
challenges for the next code generations (Gioncu, 2006), but the most important
are:
- It is a stringent necessity to have common research works with the

seismologists and engineering seismologists, in order to establish the presence
and type of faults, especially in highly urbanized zones, where near-source
effects can be very disastrous, even for low magnitude earthquakes.

- The code provisions must present different design philosophies and

computation procedures in function of fault type, producing interplate,
intraplate or intraslab earthquakes. They include different spectra, influence of
ground motion duration, number of important pulses, effects of high vibration
modes, differences in ductility demands, etc.

10.3.2 Seismic Demands and Structural Capacity Balance

The basic concepts of today's seismic codes were born almost 70 years ago, when
the knowledge about the seismic actions and structural response were rather poor.
Today, the earthquake-resistance has grown within the new multi-disciplinary
fields of Engineering Seismology and Earthquake Engineering, where many
exciting developments are predicted in the near future.
The challenge for a proper seismic design is to solve the balance between
seismic demand and structure capacity (Gioncu and Mazzolani, 2006). The seismic
demand corresponds to the effect of the earthquake on the structure and depends on