With conventional force-based seismic design, the most important information for the structural L_f u<W
engineer has been the effective peak ground acceleration. This number is comparatively X+l &MD
insignificant in displacement-based or performance-based seismic design, where the key data are /S2 9\^
peak spectral response displacement, and the “corner” period at which this occurs. There appears U\N|hw#f!!
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, 2=H3yEJq
which the structural engineer views with concern, since ductile structural response will often be in
VgfA&?4[
this region of the corner period. Dependable information on the reduction of displacement YGp8./ma<I
response with damping or ductility is also needed for design approaches utilizing secant stiffness YE<_a;yh1
characterization. Other areas needing clarification include the issue of how to develop 0IHc yb
accelerograms for time-history analysis compatible with the design seismicity using an acceptably R"Q=U}?$
small number of accelerograms, and how to reconcile the statistical nature of seismicity #X&`gD W
characterization with the structural engineer’s preference for deterministic analysis. There is some BMlnzi
evidence that a consequence of this is invalid averaging of response characteristics by structural fbF *C V
engineers.
