With conventional force-based seismic design, the most important information for the structural h4Xc Kv+
engineer has been the effective peak ground acceleration. This number is comparatively WYwzo V-
insignificant in displacement-based or performance-based seismic design, where the key data are ;'=VrE6
peak spectral response displacement, and the “corner” period at which this occurs. There appears *CeQY M
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, UsLh)#}h
which the structural engineer views with concern, since ductile structural response will often be in YKP=0 j3,
this region of the corner period. Dependable information on the reduction of displacement J 16=!q()
response with damping or ductility is also needed for design approaches utilizing secant stiffness |?x^8e<*
characterization. Other areas needing clarification include the issue of how to develop 1Q&cVxA"\
accelerograms for time-history analysis compatible with the design seismicity using an acceptably vIVw'Z(g}
small number of accelerograms, and how to reconcile the statistical nature of seismicity rDIhpT)a
characterization with the structural engineer’s preference for deterministic analysis. There is some
09
evidence that a consequence of this is invalid averaging of response characteristics by structural Z!wD~C"D73
engineers.
