With conventional force-based seismic design, the most important information for the structural wWx{#!W
engineer has been the effective peak ground acceleration. This number is comparatively "{+2Q
insignificant in displacement-based or performance-based seismic design, where the key data are k:V9_EI=
peak spectral response displacement, and the “corner” period at which this occurs. There appears zC:Pg4=w]
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, hl0X, G+@
which the structural engineer views with concern, since ductile structural response will often be in =mX26l`B
this region of the corner period. Dependable information on the reduction of displacement 9BlpqS:P&
response with damping or ductility is also needed for design approaches utilizing secant stiffness o=!_.lDF:
characterization. Other areas needing clarification include the issue of how to develop :!cK?H$+
accelerograms for time-history analysis compatible with the design seismicity using an acceptably UsA fZg8
small number of accelerograms, and how to reconcile the statistical nature of seismicity O..{ wdZy
characterization with the structural engineer’s preference for deterministic analysis. There is some ]5@n`;&#.
evidence that a consequence of this is invalid averaging of response characteristics by structural ^AI02`c.
engineers.
