StructLib

IS 456 reinforced-concrete design, from calculation to reviewable output.

An open-source Python library and visual workbench for bounded supported beam, torsion, column, slab, wall, staircase, deep-beam, flat-slab, and footing workflows under IS 456:2000.

Quick start · Product tour · Documentation · API reference · Contributing

Important

v0.24.0 is a normal software release of the audited supported scope. Support is case-qualified, not a claim of complete IS 456 coverage or professional design approval. Outputs require independent review by a qualified structural engineer before engineering or construction use. Broader library development and the one cumulative practicing-engineer review remain in progress. The exact release is available from PyPI and GitHub Releases; the current-release page links its append-only artifact and verification evidence.

One workflow, four useful surfaces

StructLib connects calculation code to the work engineers and developers need around it: importing analysis data, running repeatable designs, inspecting the result, and producing usable deliverables.

Surface	Best for	What it provides
Python package	Engineering scripts and notebooks	Typed functions, explicit units, structured results
CLI	Repeatable jobs and automation	Design → detail → BBS → DXF → report pipelines
FastAPI	Application integration	REST, WebSocket, and streaming workflows
React workbench	Visual review	CSV import, batch design, 3D inspection, dashboard, exports

From model data to reviewable deliverables

1. Import beam data from ETABS, SAFE, STAAD, or a generic CSV.
2. Design individual members or a complete batch through the same Python core.
3. Review geometry, reinforcement, governing utilization, and clause-linked checks.
4. Export BBS, DXF, HTML/PDF reports, summaries, and project quantities.

See the real application

These are unedited captures from the bundled 153-beam, six-story visualization and member-batch fixture running against the local FastAPI backend. The fixture does not claim whole-building load generation, analysis, load-path reconciliation, or professional approval.

Import with context. Confirm member count, stories, dimensions, actions, materials, and 3D positions before design.	Review the building visually. Filter by floor, select members in 3D, and compare results in an engineering table.
Understand the batch. See pass/fail status, utilization, critical members, material quantities, story summaries, and export actions.

Open the full product tour →

Quick start

Install the Python package

python3 -m pip install "structural-lib-is456==0.24.0"

The package is installed as structural-lib-is456 and imported as structural_lib.

0.24.0 is the current normal release, so ordinary package resolution selects it. Here, normal means a final PEP 440 version rather than an alpha, beta, or release-candidate version string; the project's development-maturity classifier remains Beta until the separately stated pre-1.0 and engineering-review boundaries are closed. Pin the exact version for reproducible work. See the release status and policy before selecting a build.

from structural_lib.design.is456 import beam

request = beam.load(
    {
        "identity": {"member_id": "B1", "story": "GF", "case_id": "ULS-1"},
        "section": {
            "span_mm": 5000.0,
            "b_mm": 300.0,
            "D_mm": 500.0,
            "d_mm": 442.0,
        },
        "materials": {"fck_nmm2": 25.0, "fy_nmm2": 500.0},
        "actions": {"mu_knm": 150.0, "vu_kn": 80.0, "tu_knm": 0.0},
        "calculation_basis": {"d_dash_mm": 58.0, "asv_mm2": 100.0},
        "source_provenance": "analysis-envelope:ULS-1",
    }
)
result = beam.design(request)

print(result.engineering_status)
print(result.to_dict())

Need the shortest beam-to-BBS path?

The canonical facade above is recommended for new integrations. Existing scripts and first-time evaluations can use the retained compatibility facade for a compact design, detailing, and bar-bending-schedule journey:

from structural_lib import api

result = api.design_and_detail_beam_is456(
    units="IS456", beam_id="B1", story="GF",
    span_mm=5500, mu_knm=160, vu_kn=85, b_mm=300, D_mm=500,
)
print(result.summary())
bbs = api.compute_bbs(result)
print(f"BBS weight: {bbs.summary.total_weight_kg:.1f} kg")

Identity names differ on two retained service functions: design_and_detail_beam_is456() uses beam_id, while design_beam_is456() uses case_id. Both routes require independent review; neither result is professional or construction approval.

Parameter names carry their units—b_mm, mu_knm, fck_nmm2—so the API boundary stays explicit.

Use the 13 family recipes for every advertised construction journey, including exact enums, evidence fields, structured errors, and valid PASS/FAIL/HOLD handling.

Optional capabilities:

pip install "structural-lib-is456[dxf]"        # DXF export
pip install "structural-lib-is456[report,pdf]" # HTML/PDF reports
pip install "structural-lib-is456[render]"     # DXF rendering

Run the full workbench

git clone https://github.com/Pravin-surawase/structural_engineering_lib.git
cd structural_engineering_lib

python3.11 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
pip install -e Python/

cd react_app && npm install && cd ..
./run.sh dev

Then open:

• React workbench: http://localhost:5173
• Interactive API docs: http://localhost:8000/docs

Choose Explore, load the bundled sample building, and open the Building Editor. See the product tour for the complete path.

Run a CLI pipeline

The sample uses the strict CLI v1 input contract: every member supplies its identity, materials, actions, detailing dimensions, and either effective depth or a complete derivation basis. A blocked row prevents calculation of the whole file; diagnostics use stderr and result JSON remains machine-readable.

python3 -m structural_lib design Python/examples/sample_beam_design.csv -o results.json
python3 -m structural_lib detail results.json -o detailing.json
python3 -m structural_lib bbs results.json -o schedule.csv
python3 -m structural_lib dxf results.json -o drawings.dxf
python3 -m structural_lib report results.json --format=html -o report/

For the bounded one-storey gravity workflow, start from the maintained open-hall example and review its explicit assumptions before changing it. The generated request contains no hidden engineering defaults.

python3 -m structural_lib gravity-v1 example > gravity-request.json
python3 -m structural_lib gravity-v1 gravity-request.json > gravity-result.json

The same request is available from Python with structural_lib.get_gravity_workflow_example_request_v1() and through the Building Gravity review page's Load maintained example action.

Supported scope

The project deliberately states its boundaries instead of hiding them behind a single “IS 456 compliant” label.

Element	Supported-case focus	Important boundary
Beams	Rectangular flexure and shear in the primary combined route; bounded torsion, flanged, doubly reinforced, detailing, and serviceability utilities	Torsion is not added automatically to the primary combined route
Columns	Rectangular/square sections, symmetric two-face interaction, directional slenderness, minimum eccentricity, and bounded detailing checks	Circular/helical utilities do not constitute complete circular-column design
Isolated footings	Concentric square/rectangular sizing, flexure, one-way shear, punching shear, bearing, and dowel transfer	Eccentric and combined-footing systems are outside the current supported route
Solid slabs	Simply supported and coefficient-method continuous one-way strips; common oriented two-way beam/wall-supported panels with built-in bounded coefficient lookup/interpolation, strips, corner torsion, detailing, span/depth and ordinary one-way shear checks	Direct deflection, irregular/concentrated-load panels, automatic shear reinforcement, flat slabs and column-supported punching remain outside the supported route

The auditable scope, source identities, unsafe cases, limitations, and release evidence are collected in the IS 456 evidence crosswalk.

Capabilities

• Design and detailing: supported beam, column, isolated-footing, and slab utilities
• Batch processing: lossless, accounted ETABS/SAFE/STAAD/Generic import into the strict beam project command
• Visual review: interactive React Three Fiber building and reinforcement views
• Engineering outputs: BBS CSV, DXF drawings, HTML/PDF reports, summaries, and BOQ
• Integration: declared Python, command-line, HTTP, WebSocket, and SSE surfaces
• Traceability: structured issues, explicit units, clause references, source identities, and bounded evidence

Architecture

React 19 + R3F  ── HTTP / WS / SSE ──▶  FastAPI  ──▶  structural_lib
react_app/                                fastapi_app/     Python/structural_lib/

The Python code follows a strict dependency direction:

Core types  →  IS 456 pure math  →  Services  →  UI / I/O

Layer	Location	Responsibility
Core types	Python/structural_lib/core/	Shared types and constants; no IS 456 math
IS 456 code	Python/structural_lib/codes/is456/	Pure calculations with explicit units and no I/O
Services	Python/structural_lib/services/	Orchestration, adapters, pipelines, and exports
UI / I/O	react_app/, fastapi_app/	Human and application interfaces

Quality and transparency

• CI covers Python 3.11 and 3.12 across Linux, Windows, and macOS.
• Golden vectors, contract checks, unsafe-case tests, artifact verification, protected-content gates, and an SBOM support the normal release evidence.
• Public APIs and outputs use explicit engineering units.
• Known exclusions are documented alongside supported cases.
• Passing software checks are evidence of implementation behavior, not a substitute for professional verification.

Start with the verification index, engineering-use checklist, and engineering disclaimer.

Documentation

Goal	Start here
Evaluate the project visually	Product tour
Use the Python package	Python quick start
Integrate the platform	Developer platform guide
Look up an API	Python API reference
Understand the architecture	Project overview
Verify supported evidence	Evidence crosswalk
Find all documentation	Documentation hub

Community

Questions, bug reports, feature proposals, and contributions are welcome.

• Ask a question
• Report a bug
• Request a feature
• Report a vulnerability privately
• Read the contribution guide
• Review the code of conduct

If this project supports your research, cite it using CITATION.cff.

License and engineering use

The software is available under the MIT License. The additional engineering-use notice explains the responsibilities that remain with the qualified engineer and project authority.

Primary references include IS 456:2000, SP:16, and IS 13920:2016. Standards text is not redistributed by this repository.

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