With conventional force-based seismic design, the most important information for the structural r=0j7^B#
engineer has been the effective peak ground acceleration. This number is comparatively ,D8&q?a
insignificant in displacement-based or performance-based seismic design, where the key data are :<UtHf<=k
peak spectral response displacement, and the “corner” period at which this occurs. There appears I -{^[p p
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, DZP*x
which the structural engineer views with concern, since ductile structural response will often be in 5Hy3\_ +
this region of the corner period. Dependable information on the reduction of displacement G Br,LN
response with damping or ductility is also needed for design approaches utilizing secant stiffness ucM.Ro=@
characterization. Other areas needing clarification include the issue of how to develop nNs .,J)
accelerograms for time-history analysis compatible with the design seismicity using an acceptably ~o Fh>9u
small number of accelerograms, and how to reconcile the statistical nature of seismicity [ ` 9^QEj
characterization with the structural engineer’s preference for deterministic analysis. There is some l
$w/Fz
evidence that a consequence of this is invalid averaging of response characteristics by structural *;X-\6
engineers.
