With conventional force-based seismic design, the most important information for the structural '9[_ w$~(
engineer has been the effective peak ground acceleration. This number is comparatively #rC/y0niH
insignificant in displacement-based or performance-based seismic design, where the key data are 2kgm)-z
peak spectral response displacement, and the “corner” period at which this occurs. There appears 0=5i\*5 p
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, +]e4c;`ko}
which the structural engineer views with concern, since ductile structural response will often be in B~ez>/H^
this region of the corner period. Dependable information on the reduction of displacement 5 O6MI4:
response with damping or ductility is also needed for design approaches utilizing secant stiffness Hb$q }1+y
characterization. Other areas needing clarification include the issue of how to develop FD-)nv2:
accelerograms for time-history analysis compatible with the design seismicity using an acceptably mzw*6e2T
small number of accelerograms, and how to reconcile the statistical nature of seismicity <5#e.w
characterization with the structural engineer’s preference for deterministic analysis. There is some kL3=7t^ 1
evidence that a consequence of this is invalid averaging of response characteristics by structural Rd$<R
engineers.
