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Project	—	Job No.	—
Calculation	Seismic Lateral — Equivalent Static	By	—
Reference	AS 1170.4:2024	Date	23 May 2026

Seismic Lateral Loads

AS 1170.4:2024 · Equivalent static method · Seismic weight → base shear → vertical distribution & torsion

Project name

Job No.

Stage 1 — Building & seismic weight (Cl 6.2.2)

One row = one level. RL in metres (base = lowest RL). Seismic weight per level = SDL × area. ψc is the live-load combination factor for earthquake mass; plant flag is informational.

12,000Total seismic weight W (kN)

14.00Building height hn (m)

Stage 2 — Base shear & vertical distribution (Cl 6.2 / 6.3)

Location (Z, Table 3.2)

kp source

Importance level

Sub-soil class (Table 6.4)

Sp (Cl 6.5)

μ (Cl 6.5)

kt (frame type, Cl 6.2.3)

T1 override (s) — blank = auto

T10.543 s

Ch(T1)1.621

kp·Z0.090

Cd = kpZ·Ch·Sp/μ0.0562

k (distribution)1.021

Base shear V674 kN

Vs (30%)202 kN

Vertical distribution — primary (100%) & secondary (30%)

Fx = (wi·hi^k / Σ wi·hi^k)·V. Cumulative storey shear and overturning moment, top → bottom.

Level	hi (m)	wi (kN)	wi·hi^k	Fx (kN)	ΣV (kN)	OTM (kNm)	Fx,30%	ΣV,30%
Roof	14.00	2,400.0	35,553	271.7	271.7	0	81.5	81.5
L4	10.50	2,400.0	26,501	202.5	474.3	951	60.8	142.3
L3	7.00	2,400.0	17,515	133.9	608.1	2,611	40.2	182.4
L2	3.50	2,400.0	8,628	65.9	674.1	4,739	19.8	202.2
L1	0.00	2,400.0	0	0.0	674.1	7,099	0.0	202.2
BASE				674.1	674.1	—	202.2	202.2

Stage 3 — Accidental torsion (Cl 6.6)

Accidental eccentricity = ±0.1·b applied to the storey force. Enter the plan dimension b for each direction; torsional moment per level T = Fx · 0.1·b.

Plan dim b — major dir (m)

Plan dim b — minor dir (m)

Level	Fx (kN)	e major = 0.1b (m)	T major (kNm)	e minor (m)	T minor (kNm)
Roof	271.7	3.00	815.2	2.00	543.5
L4	202.5	3.00	607.6	2.00	405.1
L3	133.9	3.00	401.6	2.00	267.7
L2	65.9	3.00	197.8	2.00	131.9
L1	0.0	3.00	0.0	2.00	0.0