Calculate design seismic action Sd(T), base shear Fb, and equivalent lateral force distribution per EN 1998-1:2004 §3.2. Lateral force method, no modal analysis required.
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Enter seismic parameters and click Calculate
Results
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g
Design PGA a_g
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g
Design Spectral Acc. S_d(T₁)
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s
Fundamental Period T₁
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kN
Base Shear F_b
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Importance Factor γ_I
—
Damping Correction η
Formulas
a_g = γ_I × a_gR
S_d(T) = a_g · S · (2.5/q) · η
F_b = S_d(T₁) · m · λ
Storey Forces
Response Spectrum S_d(T)
EN 1990 Seismic Combination
ψ_E,i = φ · ψ_2,i (EN 1998-1 §4.2.4)
Office floor (Cat B)
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φ=0.5 × ψ_2=0.3
Roof (inaccessible)
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φ=1.0 × ψ_2=0.0
S_d(T) = a_g · S · [2/3 + T/T_B·(2.5/q − 2/3)] §3.2.2.5 eq.3.14. F_b = S_d(T₁) · m · λ §4.3.3.2 eq.4.5. Modal response spectrum analysis (§4.3.3.3) is out of scope for this free tool — use the lateral force method.