With conventional force-based seismic design, the most important information for the structural }YUUC q&
engineer has been the effective peak ground acceleration. This number is comparatively i'&KoR ?
insignificant in displacement-based or performance-based seismic design, where the key data are KWtLrZ(j
peak spectral response displacement, and the “corner” period at which this occurs. There appears ngF5ywIG
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, "q@OM f
which the structural engineer views with concern, since ductile structural response will often be in fy|ycWW>8
this region of the corner period. Dependable information on the reduction of displacement @y:mj \J9
response with damping or ductility is also needed for design approaches utilizing secant stiffness %gj's-!!
characterization. Other areas needing clarification include the issue of how to develop /3|uU
accelerograms for time-history analysis compatible with the design seismicity using an acceptably cx%[hM09
small number of accelerograms, and how to reconcile the statistical nature of seismicity -L e:%q2
characterization with the structural engineer’s preference for deterministic analysis. There is some lF-;h{
evidence that a consequence of this is invalid averaging of response characteristics by structural W+k`^A|@
engineers.
