Challenges for the Next Generation of Seismic Codes - Earthquake Engineering for Structural Design - page 455

seismological studies. Therefore, the structural designer must be fully
aware of the fact that “… it useless to determine with great accuracy
the structure response for a given seismic action if this one is
establishedwithagreatlevelofincertitude”.

(iv) The definition of a major earthquake action inevitably calls for a series

of seismological knowledge, structural engineering judgments and
safety policy. The reduction (not the elimination) of uncertainties in
ground motion modeling is now the main challenge in structural
seismic design. For this reason, the proper seismic design should be
elaborated in close collaboration between seismologists, experts in
faults characteristics, and structural engineers, who know very well
the structural response to a given ground motion. In many cases, this
collaboration is very difficult, due to the differences in education,
being the differences between science and engineering. In order to fill
this gap, engineers must especially work in the Engineering
Seismology branch, in order to transform the qualitative knowledge of
Seismology into quantitative values to be used by Earthquake
Engineering and to partially eliminate the incertitude in determining
the seismic actions as a function of the fault type.

(v) A significant gap exists between the existing level of research results

and the provisions of design codes. In many cases the research works
are performed by professors and researchers, who are more interested
in publishing their results for promotion among their colleagues, than
in the transmission of new knowledge to those who will apply it (De
Buen, 1996).

(vi) Structural engineers are conservative professionals and not researchers

in new directions of structural design. Their activities are driven by the
need to deliver the design in a timely and cost-effective manner. They
may also resist new concepts, unless these concepts are put into the
context of their present mode of operation (Krawinkler, 1995).
Therefore, during the elaboration of new codes it must be kept in mind
that the design engineering community tends to be conservative. So,
the new code provisions must be a compromise between new and old
knowledge and procedures. Otherwise, the structural designers will
reject the new methodologies.

(vii) The implementation of new concepts in codes is constrained by the

need to keep the design process simple and verifiable. Today, the
progress of computer software has made it possible to predict the
actual behavior of structures subjected to seismic loads using non-
linear analysis. But designers are always pressed by the deadline to
deliver the project, therefore, only for very special structures can they
accept to use advanced design methodologies. For the majority of
designed buildings, they request to use only simple procedures. This is
the reason why, for instance, despite the progress in design
methodologies for evaluating the structural ductility, the codes contain