With conventional force-based seismic design, the most important information for the structural kk4 |4
engineer has been the effective peak ground acceleration. This number is comparatively !$I~3_c
insignificant in displacement-based or performance-based seismic design, where the key data are 4 jT6 h9%
peak spectral response displacement, and the “corner” period at which this occurs. There appears 1 ]xk:u4LA
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, /2^L;#
which the structural engineer views with concern, since ductile structural response will often be in CEfqFn3^
this region of the corner period. Dependable information on the reduction of displacement B-I4(w($
response with damping or ductility is also needed for design approaches utilizing secant stiffness X9>fE{)!
characterization. Other areas needing clarification include the issue of how to develop .)E#*kLWR
accelerograms for time-history analysis compatible with the design seismicity using an acceptably mF ~T?L"
small number of accelerograms, and how to reconcile the statistical nature of seismicity L!f~Am:#
characterization with the structural engineer’s preference for deterministic analysis. There is some %h. zkocM
evidence that a consequence of this is invalid averaging of response characteristics by structural r&=ulg
engineers.
