Simplified Interpretation of Exceptions under Section 11.4.8:
Structures other than Seismically isolated or Structures with Damping Systems
When Ss ≥ 1.0
For Site Class E:
→ Fa = Fa of Site Class C
When S1 ≥ 0.20
For Site Class D:
→ Cs calculated per Eq. 12.8-2 if T ≤ 1.5Ts
→ 1.5Cs where Cs is calculated per Eq. 12.8-3 if TL ≥ T > 1.5Ts
→ 1.5Cs where Cs is calculated per Eq. 12.8-4 if T > TL
For Site Class E:
→ T ≤ 1.5Ts and Equivalent Static Force procedure is used.
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