Syed Nafiz Reja Hasib

Civil and structural engineer

Contact
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ShellForm: the carbon cost of seismic resilience in form-found concrete shells

How much embodied carbon does earthquake resistance cost in a form-found concrete shell, and does form-finding that includes seismic loads deliver it more cheaply than thickening a gravity-only shape? 168 sized designs and an interactive explorer.

Year
2026–
Status
In progress
Methods
Form-finding, Seismic analysis, Embodied carbon, Finite elements, Interactive tools
Tools
Python, CalculiX, three.js
Thin concrete shell on four corner supports, 20 m span, coloured by how much the seismic-aware form rises or drops relative to the gravity-only form; the largest change is about 349 millimetres.
ShellForm · L20-corners-r0.20Seismic-aware form at Sa = 0.6 g, coloured by height change from the gravity-only form (blue lower, red higher; scale ±349 mm; in this cell no node drops). 20 m span, corner supports, rise/span 0.2. Data: ShellForm v0.1.0, tag freeze-2026-11-09, on ShellBench v0.3.0.

Key numbers

Sized designs
168shells
2 spans × 2 support cases × 3 rises × 2 strategies × 7 Sa levels
Decision rule
5%
Pre-registered: a strategy counts as cheaper only if it saves at least this much
Seismic demand range
0–0.6g
Code-independent Sa range; GB 50011 and Eurocode 8 sites marked

Question

How much embodied carbon does seismic resilience cost in a form-found concrete shell, and does form-finding that includes seismic loads deliver it more cheaply than thickening a gravity-only shape?

ShellForm extends the seismic form-finding of Michiels and Adriaenssens (2017, 2018) by sizing each form to pass code checks and counting its A1–A3 embodied carbon.

Approach

  • Design space. 2 spans × 2 support cases × 3 rise ratios × 2 strategies (gravity-only, seismic-aware) × 7 spectral acceleration levels = 168 sized designs, across a code-independent seismic demand range of 0–0.6 g, with Chinese (GB 50011) and Eurocode 8 sites marked.
  • Sizing. Each form is thickened in 5 mm steps until it passes its checks, including linear buckling and a 50 mm minimum thickness, then given its reinforcement.
  • Carbon. A1–A3, reported under two factor sets (GB/T 51366 and ICE).
  • Decision rule. Pre-registered: a strategy counts as cheaper only if it saves 5 % or more.
  • Record. Code frozen at tag freeze-2026-11-09 on ShellBench v0.3.0; every number traces to a file in results/. ShellForm never copies a ShellBench value.

Validation

ShellForm is built on ShellBench’s validated, tagged modules, whose shell analysis reproduces the Scordelis–Lo roof and pinched hemisphere benchmarks within 0.4 %. The new seismic form-finding code has its own validation tests; the suite stood at 101 passing tests on 10 November 2026.

Findings in brief

Across the design space, adding seismic load to form-finding changes the shape of the shell much more than the amount of material in it. The reason lies in the sizing: thickness and steel are governed by checks that do not respond to the seismic demand studied. The full comparison, the mechanism and the robustness checks are in the manuscript in preparation.

What this does not show

  • Shells are studied as isolated roofs on idealised supports, not as part of a building.
  • Seismic demand is applied through a code-independent spectral acceleration range; site-specific hazard is not modelled.
  • Carbon is cradle-to-gate (A1–A3); formwork and construction are excluded.
  • The manuscript is in preparation; the findings follow a pre-registered rule but are not yet peer reviewed.

Evidence

Benchmark
Shell analysis inherited from ShellBench v0.3.0 (Scordelis–Lo roof, pinched hemisphere); new validation tests for the seismic form-finding code
Metric
Computed / reference displacement
Result
0.9984 and 0.9965
Code
github.com/syednafizreja/ShellForm
Release
v0.1.0
DOI
10.5281/zenodo.24084110
Tests
101 passed (pytest, 10 Nov 2026)
Licence
MIT
Gallery of 10 metre shells: the gravity-only form, the height change of the seismic-aware form at spectral accelerations of 0.3 g and 0.6 g, and the mid-plan section.
Fig. 1, 10 m gallery: gravity-only form, height change of the seismic-aware form at Sa 0.3 g and 0.6 g, and the mid-plan section. Freeze run, tag freeze-2026-11-09.
The ShellForm design explorer with controls, a 3D view of the seismic-aware form coloured by height change, a comparison panel, carbon against Sa and a matrix of every comparison.
The design explorer: pick span, supports, rise and Sa to compare both strategies side by side. Runs offline in any browser.
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ShellBench

How much do thin-shell floors cut the A1–A3 embodied carbon of GB 50010 / GB 50011 reinforced concrete frames across 3–8 storeys, and how does the saving change with storey count and seismic intensity once diaphragm, tie and topping needs are met?

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Canopy carbon tool

An interactive research prototype that links canopy geometry to structural response, material volume and embodied carbon for a thin shell canopy on tree columns, so the trade-off can be explored live in the browser.