Seismic Codes & Configuration
The architect's seismic lesson — shape decides whether a building survives.
This is the heart of the course for an architect, because building configuration — the shape, symmetry and regularity decided at concept stage — does more for earthquake safety than any later structural fix. A symmetric, regular building survives; an irregular one with a soft ground storey, a short column, re-entrant corners or torsion fails, however much steel is added. This unit covers the seismic code provisions and the Indian codes (IS 1893, IS 4326, IS 13920), then the configuration rules every architect must internalise. Test a configuration with the checker.
Learning objectives
By the end of this unit, you will be able to — mapped to the course outcomes for Earthquake Resistance Architecture:
Identify the Indian seismic codes (IS 1893, IS 4326, IS 13920) and what each governs.
Explain the four virtues of an earthquake-resistant building.
Apply configuration rules — symmetry, regularity, proportion — at concept stage.
Identify configuration flaws — soft storey, short column, re-entrant corner, torsion — and avoid them.
Codes & the four virtues
The Indian codes set the forces and detailing; the four virtues — configuration, stiffness, strength, ductility — put configuration first because it is set at concept stage.[1, 2]
IS 1893, 4326, 13920
India's seismic design is governed by a family of IS codes: IS 1893 (Part 1) gives the criteria and the design forces (zones, soil, importance, response); IS 4326 covers earthquake-resistant design and construction of buildings; IS 13920 gives the DUCTILE DETAILING of reinforced-concrete members; IS 13828 covers improving the earthquake resistance of low-strength masonry; and IS 13935 covers repair and seismic strengthening. The architect need not do the calculations, but must know these exist and design WITHIN them from the start.[1]
The configuration rules
Keep it simple, symmetric and regular; avoid torsion, re-entrant corners, the soft/weak storey and the short column — the shape decides whether the engineer's job is possible.[2]
Simple, symmetric, regular
The golden rule: keep the building SIMPLE, SYMMETRIC and REGULAR in both plan and elevation. A compact, symmetric plan (square, circle, rectangle within proportion) with mass and stiffness evenly distributed shakes uniformly and survives. Long, thin, complex or asymmetric plans twist and tear. If a complex plan is needed, SEPARATE it into simple, regular blocks with seismic gaps. Good seismic configuration is mostly good, disciplined planning.[2]
Check a configuration
Toggle the configuration flaws on a building and watch the seismic-configuration risk grow — a reminder that no amount of steel fully rescues a bad shape.
Configuration check · toggle the flaws
100
/ 100 config
Well configured — a good seismic shape.
Indicative — configuration is the architect's most powerful seismic decision, set at concept stage.
At a glance
| Aspect | One | The other |
|---|---|---|
| Most powerful seismic tool | Adding steel later | Good configuration at concept stage |
| Plan shape | L/T/U, long, asymmetric: twist & tear | Compact, symmetric, regular: survives |
| Ground storey | Open soft storey: crushes | Continuous/braced storey: safe |
| Failure mode wanted | Brittle: sudden collapse | Ductile: bends, warns, stands |
| Mass & stiffness centres | Apart: torsion | Together: no twist |
Key terms
The Indian seismic codes — criteria/forces; design & construction; RC ductile detailing.
Configuration, lateral stiffness, lateral strength and ductility (Murty).
The ability to bend and absorb energy without sudden brittle failure — 'bend, don't break'.
The shape, symmetry and regularity of a building — the architect's most powerful seismic decision.
Twisting when the centres of mass and stiffness don't coincide; the far edges fail.
The inside corner of an L/T/U/+ plan that concentrates stress and tears.
An open, flexible ground floor below solid storeys that crushes — the leading Indian failure.
A column shortened by an infill/mezzanine that attracts huge force and shatters.
Studio task
Take a building design (yours or a real one) and run it through the configuration checker honestly — does it have a soft storey, short columns, re-entrant corners, asymmetry? For every flaw, sketch the fix (separate the wings, brace the ground storey, balance the mass). Then redraw the plan as a compact, symmetric, regular configuration and explain why it would survive where the original would fail.
Self-assessment
1. For earthquake safety, the most powerful decision the architect makes is —
2. A 'soft storey' is dangerous in an earthquake because —
3. 'Ductility' in earthquake-resistant design means a building that —
Recap
References & further reading
- [1]BIS — IS 1893 (Part 1), IS 4326, IS 13920, IS 13828, IS 13935 (Indian seismic codes).
- [2]Murty, C.V.R., Goswami, R., Vijayanarayanan, A.R. & Mehta, V. — Some Concepts in Earthquake Behaviour of Buildings (Gujarat State Disaster Management Authority / NICEE); Murty & Charleson — earthquake design concepts.
Further reading
- C.V.R. Murty et al. — Some Concepts in Earthquake Behaviour of Buildings (free).
- Andrew Charleson — Seismic Design for Architects.
- BIS — IS 1893, IS 4326, IS 13920.
Sources gathered and fact-checked June 2026. Published values vary by source, sample and method — treat as indicative and confirm against the cited standard before structural use.