Challenges for the Next Generation of Seismic Codes - Earthquake Engineering for Structural Design - page 464

earthquakes for probability of exceedance of 2%, moderate earthquakes for 10%
and large earthquakes. Two design steps are considered in the code: the first refers
to low earthquakes and the second to the large ones, corresponding to no collapse
level (Shen and Shi, 2004).
The new code 2001 contains some very important improvements in comparison
with the 1989 version (Wang, 2001). These modifications refer to the earthquake
force levels, the seismic design parameters, the seismic design response spectra,
the site classification, the input earthquake for time history analysis of structures,
the minimum required shear force of story, the two phases of seismic design, the
elastic analysis for design of sections, the design for minor earthquakes, the elasto-
plastic analysis for the displacement response of structures for major earthquakes.
The seismic intensity for the four degree is replaced by the peak accelerations:
zone I, peak acceleration 0.05g, zone IIa with 0.10g, zone IIb with 0.15g, zone IIIa
with 0.20g, zone IIIb with 0.30g, and zone IV with 0.40g. It is interesting to note
that the corner periods T g are given for near-source and far-source (considering
both earthquake intensity and epicenter distance), in function of site classes (in
seconds): zone I, 0.20 and 0.25, zone II, 0.3 and 0.4, zone III, 0.40 and 0.55, zone
IV, 0.65 and 0.85 (the first values correspond to near-source, the second ones to
far-source cases). These values generally increase with the soil conditions, the
percentage not exceeding 40 to 50%, smaller for low intensities and larger for high
intensities. A very detailed verification of story drifts for minor and large
earthquakes is required, in function of structure type (including reinforced
concrete, steel and masonry buildings).
10.2.5 Europe
The codification activity in Europe is characterized by three distinct periods.
During the first, each European country elaborated its national code, in function of
experiences and traditions in design against earthquakes. During the second, a set
of pan-European model codes was developed by the European Committee for
Standardization (CEN), in the frame of activity for the elaboration of the
Eurocodes, being characterized by the co-existence of national and European
codes. In the last periods, the Eurocodes will replace the national codes in all
countries belonging to European Union.
Seismological aspects. Europe seismicity is characterized by very various
tectonic conditions expressed by different source mechanisms. There are three
main regions with different source types, showing the very complex tectonic
behavior:
- Mediterranean seismic region (Marcellini et al, 1998, Vannucci et al, 2004)
results from two major processing. In South, the tectonic displacements caused
by the subduction of the African plate underneath the Eurasian plate.
Exceptions are the Sicily and the Hellenic arc, where the intermediate intraslab
earthquakes are dominant. The South European fault belongs to the Alpine-
Himalayan belt, the second in importance after the Circum-Pacific Ring. The
North fault system is due to the collision of some blocks against Europe: the