With conventional force-based seismic design, the most important information for the structural E rrs6
engineer has been the effective peak ground acceleration. This number is comparatively crbph.0
insignificant in displacement-based or performance-based seismic design, where the key data are %E k!3t
peak spectral response displacement, and the “corner” period at which this occurs. There appears :?P>))vT%
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, hqW),^\>'
which the structural engineer views with concern, since ductile structural response will often be in [q!/YL3 %
this region of the corner period. Dependable information on the reduction of displacement (Zz8 ldO
response with damping or ductility is also needed for design approaches utilizing secant stiffness Rh,a4n?W
characterization. Other areas needing clarification include the issue of how to develop dQQ!QbI(.
accelerograms for time-history analysis compatible with the design seismicity using an acceptably 'o]k Op@q
small number of accelerograms, and how to reconcile the statistical nature of seismicity }Sr=|j
characterization with the structural engineer’s preference for deterministic analysis. There is some @9e}kiW
evidence that a consequence of this is invalid averaging of response characteristics by structural AeR*79x
engineers.
