What Is Direct Displacement-Based Design (DDBD)?
DDBD (the Priestley's — the displacement's; the substitute) designs (the structure's — the target's; the drift's) for (the displacement — the spectrum's; the Sd's) via (the SDOF's — the equivalent; the effective's). The design: the target's (the 2%'s — the drift's; the chosen), the damping's (the hysteretic's — the 15-30%; the equivalent's), and the base shear's (the derived — the Ke's; the 1/T's). The seismic's — the displacement designed.
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How DDBD works
The target (the 2%'s — the drift's; the performance's — the chosen), the SDOF (the substitute's — the equivalent; the Me's — the mass), the damping (the hysteretic's — the 15-30%; the ductility's — the derived), the spectrum (the displacement's — the Sd's; the Te's — the effective), and the shear (the Ke's — the 4π²Me/Te²; the distributed).
The procedure
The profile (the displaced's — the shape's; the inelastic's), the yield (the displacement's — the Δy's; the estimated), the ductility (the mu's — the Δd/Δy's; the damping's), the verification (the NLTHA's — the 7's; the checked), and the iteration (the 1-2's — the cycles'; the converged).
Applications
The bridges' (the Caltrans' — the adopted; the SDC's), the buildings' (the tall's — the PBSD's; the peer's), the retrofit (the target's — the achieved; the 41's), and the codes' (the informer's — the NZ's; the EN's). The DDBD is the rational — the displacement's target, the damping's equivalent.
The bottom line
Apply DDBD (Priestley: target drift → equivalent SDOF → hysteretic damping 15-30% → displacement spectrum → base shear Ke=4π²Me/Te²) for bridges and PBSD buildings — verify with NLTHA; adopted by Caltrans.
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