With conventional force-based seismic design, the most important information for the structural T/xp?Vq6/
engineer has been the effective peak ground acceleration. This number is comparatively ?- ^m`
insignificant in displacement-based or performance-based seismic design, where the key data are Y$Y_fjd_
peak spectral response displacement, and the “corner” period at which this occurs. There appears J6%AH?Mt
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, & )vC;$vD`
which the structural engineer views with concern, since ductile structural response will often be in {%{ `l-
this region of the corner period. Dependable information on the reduction of displacement 2Sp=rI
response with damping or ductility is also needed for design approaches utilizing secant stiffness @t`Xq1
characterization. Other areas needing clarification include the issue of how to develop pN9A{v(
accelerograms for time-history analysis compatible with the design seismicity using an acceptably gk+ h8 LZ
small number of accelerograms, and how to reconcile the statistical nature of seismicity %8D z o
characterization with the structural engineer’s preference for deterministic analysis. There is some D
<&X_
evidence that a consequence of this is invalid averaging of response characteristics by structural M57T2]8,
engineers.
