With conventional force-based seismic design, the most important information for the structural g k[8'
engineer has been the effective peak ground acceleration. This number is comparatively LN?W~^gsR
insignificant in displacement-based or performance-based seismic design, where the key data are y\&`A:^[ A
peak spectral response displacement, and the “corner” period at which this occurs. There appears h~
=UFE%'
to be a disagreement between seismologists on opposite sides of the Atlantic about these data, C2< /.jeLa
which the structural engineer views with concern, since ductile structural response will often be in 8 ?O6IDeW
this region of the corner period. Dependable information on the reduction of displacement Wf= D'6w
response with damping or ductility is also needed for design approaches utilizing secant stiffness 5}4r'P$m:
characterization. Other areas needing clarification include the issue of how to develop !8U\GR `
accelerograms for time-history analysis compatible with the design seismicity using an acceptably 5l"v : Px
small number of accelerograms, and how to reconcile the statistical nature of seismicity .pOTIRb A
characterization with the structural engineer’s preference for deterministic analysis. There is some /u 8m|S<
evidence that a consequence of this is invalid averaging of response characteristics by structural xeX Pc7JG
engineers.
