What Is Base Isolation vs. Energy Dissipation?
Both (the seismic — the protection's; the 17/18's) reduce (the demands — the 3-4x; the isolated/damped) — the isolation (the period's — the 2-3s; the shifted) decouples (the ground's — the 17's; the bearings'), while the dissipation (the damping's — the 20-40%; the added) absorbs (the energy's — the 18's; the dampers'). The isolation's — the period shifted; the dissipation's — the energy absorbed.
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Base isolation (Ch. 17)
The 2-3s (the period's — the shifted; the 0.5's — the fixed), the bearings (the LRB's — the lead's; the FPS's — the friction's; the HDR's), the 3-4x (the reduction's — the superstructure's; the elastic's), the moat (the 24-36 inch — the clearance; the MCE's), and the 17 (the chapter's — the 2-procedure's; the peer's — the required).
Energy dissipation (Ch. 18)
The 20-40% (the damping's — the effective; the added), the dampers (the viscous' — the F=Cv; the BRB's — the yielding's; the friction's), the 2-3x (the reduction's — the drift's; the force's), the 18 (the chapter's — the devices'; the tested's — the 1.0's), and the retrofit (the added — the existing's; the minimal's — the disruption).
Selection
The isolation's (the new's — the 4-story's; the stiff's — the ideal), the dissipation's (the retrofit's — the tall's; the wind's — the dual), the cost (the 5-10%'s — the isolation's; the 3-5%'s — the dampers'), and the combined (the isolated-damped's — the 40%'s; the optimal's). The isolation shifts — the dissipation absorbs.
The bottom line
Choose base isolation (Ch. 17, 2-3s period, 3-4x demand reduction, 24-36-in moat) for new stiff low-rise buildings and energy dissipation (Ch. 18, 20-40% added damping, 2-3x reduction) for retrofits and tall buildings — combine for optimal performance.
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