Home / Calculators / IS 1893 Seismic 🇮🇳 IN

IS 1893 (Part 1):2016 — Seismic Base Shear

Ah = (Z/2)·(I/R)·(Sa/g) · VB = Ah·W · storey force distribution (height-squared form)

⚠ Beta — R must be user-supplied

Zone factor Z and importance factor I are commonly-cited values. R (response reduction factor) depends on the lateral system and IS 13920 ductile detailing — its table is supplied here for reference but you must confirm the classification against Table 9 before entering R. The Sa/g spectrum uses a simplified 5%-damping form, not the full 2016-edition procedure.

Input data

Confirm against the official zone map for the project site
Confirm system classification against Table 9 before relying on this value

Results

Z—
I—
R—
Sa/g—
Ah = (Z/2)(I/R)(Sa/g)—
VB = Ah·W (kN)—
REFERENCES
§6.4.2 Eq.(6)Ah = (Z/2)·(I/R)·(Sa/g)
§7.5.3 Eq.(7)VB = Ah·W
§7.7.1 Eq.(14)Qi = VB·Wi·hi²/Σ(Wj·hj²) — note the height-SQUARED form, unlike the linear GB/EC8 distributions
Table 3 / Annex EZone factor Z by seismic zone map
Table 9Response reduction factor R by system
© CopyrightIS codes are copyright BIS. Only clause numbers cited.

Engine: in-codes.js · IN-IS456-2000.v1-beta ·

← IS 456 Flexure

Sa/g design spectrum

Simplified 5%-damping three-branch form by soil type. NOT the full IS 1893:2016 procedure — verify against §6.4.5, Figure 2.

Storey force distribution

Storeyh (m)W (kN)W·h²Qi (kN)Vi (kN)

Step-by-step

Preliminary tool. Final seismic design requires the full official IS 1893:2016 text, IS 13920 ductile detailing compliance, and review by a licensed structural engineer.