Work out seismic load instantly with clear inputs, formula shown and shareable results.
The equivalent static method expresses seismic demand as a fraction of the building's own weight: Ah = Z I (Sa/g) / (2 R). The zone factor sets regional hazard, importance reflects consequence of failure, the spectral acceleration ratio captures the building period and R credits the ductility of the structural system. Base shear is that coefficient times seismic weight.
Design coefficient
Ah = Z x I x (Sa/g) / (2 R), with Sa/g taken as 2.5 in the plateau region
Base shear
Vb = Ah x seismic weight
Preliminary estimate only. Seismic design must be performed by a qualified structural engineer to the seismic code in force, including period calculation, storey distribution and drift checks.
Ah = Z x I x (Sa/g) / (2 R), with Sa/g taken as 2.5 in the plateau region. The equivalent static method expresses seismic demand as a fraction of the building's own weight: Ah = Z I (Sa/g) / (2 R).
R credits inelastic energy dissipation. A ductile moment frame with R = 5 is designed for a fifth of the elastic force because it is detailed to yield without collapsing.
This calculator takes 4 inputs: Seismic weight of building, Zone factor Z, Importance factor I, Response reduction factor R. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.