structural-lib-is456

IS 456 RC Beam Design Library (Python package).

Version: 0.24.0a1 (Alpha development preview) Status:

⚠️ Development Preview: APIs may change until v1.0. For reproducible results, pin to a release tag.

Supported-case boundary: this package implements selected IS 456 workflows, not the whole standard. Every output requires independent verification and qualified structural-engineering review. Use official standards as the authoritative source.

New in v0.24.0a1

• Fail-closed project intake: malformed, missing, unknown, or mixed-validity beam rows block the whole project instead of being defaulted or skipped.
• Safe public CLI: design keeps JSON on stdout, sends diagnostics to stderr, exits non-zero on blocked input, and preserves the bbs/detail/dxf chain.
• Traceable results: import ledgers, input/result provenance, API classification, and qualified-review boundaries are explicit and machine-readable.
• Additional bounded workflows: braced walls, straight-flight staircases, simply supported deep beams, regular interior flat slabs, symmetric combined footings, and property-line strap footings expose case-qualified APIs.
• Release evidence: exact-wheel UAT covers 29 positive and negative cases across all 12 advertised commands, with hosted and local verdicts aligned.

Install

pip install structural-lib-is456===0.24.0a1       # prepared candidate artifact
pip install "structural-lib-is456[dxf]===0.24.0a1" # candidate with DXF export
python -m structural_lib install-preflight          # interpreter/origin/extras

0.24.0a1 is prepared but not tagged or published. These pins are exercised against the exact local wheel during candidate verification; 0.23.1a2 remains the current public Alpha unless a separate owner-authorized release occurs.

Requires Python 3.11+. On Python 3.9–3.10, pip installs the older v0.16.x (beam-only, no column/footing).

If You Want To…

Design a Beam (IS 456 flexure + shear)

from structural_lib import design_beam_is456

result = design_beam_is456(
    units="IS456", b_mm=300, D_mm=500, d_mm=450,
    fck_nmm2=25, fy_nmm2=500,
    mu_knm=150, vu_kn=100,
)
print(f"Ast = {result.flexure.Ast_required:.0f} mm²")
print(f"Safe? {result.flexure.is_safe}")

Get Detailing (bar sizes, stirrups, cut lengths)

from structural_lib import build_detailing_input, compute_detailing

detailing_input = build_detailing_input(
    result, beam_id="B1", b_mm=300, D_mm=500, d_mm=450,
    span_mm=6000, cover_mm=30, fck_nmm2=25, fy_nmm2=500,
)
detailed = compute_detailing(detailing_input)

for beam in detailed:
    print(f"{beam.beam_id}: {len(beam.top_bars)} top, {len(beam.bottom_bars)} bottom zones")

Generate a Bar Bending Schedule (BBS)

from structural_lib import compute_bbs

bbs = compute_bbs(detailed, project_name="My Project")
print(f"Total weight: {bbs.summary.total_weight_kg:.1f} kg")
for item in bbs.items:
    print(f"  {item.bar_mark}: ø{item.diameter_mm:.0f} × {item.no_of_bars} nos")

Export DXF Drawings

from structural_lib import compute_dxf

output_path = compute_dxf(detailed, "beam.dxf")  # returns Path
print(f"DXF saved to {output_path}")

Requires the dxf extra: pip install "structural-lib-is456[dxf]"

Generate an HTML Report

from structural_lib import compute_report

html = compute_report(detailing_input, format="html")
with open("report.html", "w") as f:
    f.write(html)

Batch Design with the Canonical Project Schema

from structural_lib.services.batch import design_project_beams_v1

batch = design_project_beams_v1(
    [
        {
            "schema_version": "project-beam-design/v1",
            "member_id": "B1",
            "b_mm": 300,
            "D_mm": 500,
            "d_mm": 442,
            "mu_knm": 150,
            "vu_kn": 100,
            "fck_nmm2": 25,
            "fy_nmm2": 500,
        }
    ]
)
print(batch.summary.to_dict())
print(batch.members[0].calculation["flexure"]["ast_required"])

Run the Full Pipeline (design → detail → BBS → report)

See examples/end_to_end_workflow.py for a complete working script (available in the source repository).

Cost-Optimize a Beam

from structural_lib import optimize_beam_cost

optimized = optimize_beam_cost(
    units="IS456", span_mm=6000, mu_knm=150, vu_kn=100,
)
print(f"Optimal: {optimized.optimal_design.b_mm}×{optimized.optimal_design.D_mm} mm")

Check Multi-Case Compliance

from structural_lib import check_beam_is456

report = check_beam_is456(
    units="IS456", b_mm=230, D_mm=500, d_mm=450,
    fck_nmm2=25, fy_nmm2=500,
    cases=[{"case_id": "ULS-1", "mu_knm": 100, "vu_kn": 80}],
)
print(f"Governing case: {report.governing_case_id}")

CLI Usage

The design command is fail-closed. CSV input must explicitly supply BeamID,Story,b,D,eff_d,Span,Cover,fck,fy,Mu,Vu,Stirrup_Dia,Stirrup_Spacing. Instead of eff_d, supply tension_bar_diameter_mm so effective depth can be derived from the explicit cover and stirrup diameter. JSON input uses the cli-beam-design-input/v1 envelope. Unknown, duplicate, malformed, non-finite, empty, ambiguous, or mixed-validity input blocks the whole project without a partial result.

python -m structural_lib design input.csv -o results.json        # Beam design
python -m structural_lib bbs results.json -o bbs.csv             # Bar bending schedule
python -m structural_lib dxf results.json -o drawings.dxf        # DXF drawings
python -m structural_lib report results.json --format=html -o report.html  # HTML report
python -m structural_lib job job.json -o output/                 # Full job from spec
python -m structural_lib --help                                  # All options

What's Available

Beam Design & Detailing

The primary combined beam route covers flexure and shear. Torsion is available only through the separate explicit torsion workflow.

Column Design (IS 456 Cl 25, 39.3–39.7)

Footing Design (IS 456 Cl 34)

Combined, strap, raft and pile-cap foundations, settlement, geotechnical design, and lateral stability are outside these footing workflows.

Solid Slab Design (Supported Cases)

Two-way coefficients are not built in or verified by the library. The two-way route requires explicit source approval and a qualified acceptance reference. Flat/drop/ribbed slabs, openings, irregular panels and FEM are excluded.

IS 13920 Ductile Detailing

Export, Import & Visualization

Full API reference: see docs/reference/api.md

License

MIT — see LICENSE.

Engineering-use conditions and professional responsibilities are described in the repository's LICENSE_ENGINEERING.md. The software is a design aid, not a substitute for official code publications, independent calculation, or professional approval.