With conventional force-based seismic design, the most important information for the structural OQA3 ~\Vu
engineer has been the effective peak ground acceleration. This number is comparatively \g}FoN&
insignificant in displacement-based or performance-based seismic design, where the key data are Y e}y_W
peak spectral response displacement, and the “corner” period at which this occurs. There appears :l>T~&/98
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, n~d`PGs?f
which the structural engineer views with concern, since ductile structural response will often be in cF[[_
this region of the corner period. Dependable information on the reduction of displacement NB&u^8b
response with damping or ductility is also needed for design approaches utilizing secant stiffness B|O/h! H.
characterization. Other areas needing clarification include the issue of how to develop | We @p
accelerograms for time-history analysis compatible with the design seismicity using an acceptably (;T; ?v`-
small number of accelerograms, and how to reconcile the statistical nature of seismicity 'g a1SbA]
characterization with the structural engineer’s preference for deterministic analysis. There is some 1Lj YV
evidence that a consequence of this is invalid averaging of response characteristics by structural *X; g
Y
engineers.
