With conventional force-based seismic design, the most important information for the structural %F0.TR!!n
engineer has been the effective peak ground acceleration. This number is comparatively ge&!G O
insignificant in displacement-based or performance-based seismic design, where the key data are `y&2Bf
peak spectral response displacement, and the “corner” period at which this occurs. There appears p" Di;3!y!
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, ukee.:{
which the structural engineer views with concern, since ductile structural response will often be in .Jc<Gg
this region of the corner period. Dependable information on the reduction of displacement -zm-|6[Wi
response with damping or ductility is also needed for design approaches utilizing secant stiffness YipL _&-
characterization. Other areas needing clarification include the issue of how to develop #.@D}7y5
accelerograms for time-history analysis compatible with the design seismicity using an acceptably B v}i#D
small number of accelerograms, and how to reconcile the statistical nature of seismicity t8#u}u
characterization with the structural engineer’s preference for deterministic analysis. There is some }SW>ysw'm
evidence that a consequence of this is invalid averaging of response characteristics by structural +=L^h9F
engineers.
