With conventional force-based seismic design, the most important information for the structural iW9o-W
a
engineer has been the effective peak ground acceleration. This number is comparatively 6Mj (B*c
insignificant in displacement-based or performance-based seismic design, where the key data are &)$}Nk
peak spectral response displacement, and the “corner” period at which this occurs. There appears n /6qc3\5i
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, d7]~t|
which the structural engineer views with concern, since ductile structural response will often be in WAUgbImc{
this region of the corner period. Dependable information on the reduction of displacement ~PtIq.BY
response with damping or ductility is also needed for design approaches utilizing secant stiffness qRc Y(mb
characterization. Other areas needing clarification include the issue of how to develop ,\RZ+kC>~
accelerograms for time-history analysis compatible with the design seismicity using an acceptably Wb%t6N?
small number of accelerograms, and how to reconcile the statistical nature of seismicity "g%=FH3e
characterization with the structural engineer’s preference for deterministic analysis. There is some &cSZ?0 R
evidence that a consequence of this is invalid averaging of response characteristics by structural R_zQiSwG<
engineers.
