With conventional force-based seismic design, the most important information for the structural K 1:F{*
engineer has been the effective peak ground acceleration. This number is comparatively $6!`
insignificant in displacement-based or performance-based seismic design, where the key data are BqZLqGO Ku
peak spectral response displacement, and the “corner” period at which this occurs. There appears m_rR e\
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, 86%weU/*
which the structural engineer views with concern, since ductile structural response will often be in vW$] :).
this region of the corner period. Dependable information on the reduction of displacement I4|p;\`fK
response with damping or ductility is also needed for design approaches utilizing secant stiffness -<z'f){gb
characterization. Other areas needing clarification include the issue of how to develop (!X:[Ah*$
accelerograms for time-history analysis compatible with the design seismicity using an acceptably ~w]1QHA'f
small number of accelerograms, and how to reconcile the statistical nature of seismicity rLL;NTN+/
characterization with the structural engineer’s preference for deterministic analysis. There is some ^D4 b\mF
evidence that a consequence of this is invalid averaging of response characteristics by structural yvDzxu
engineers.
