Supported and self-supporting cone, dome, and umbrella roof design for atmospheric tanks (IS 803-1976, §6.4)
◉ IS 803-1976 §6.4 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only, and distinct from the existing API 650-based Roof Design calculator. India's own domestic tank code, verified directly against this edition's page images. The frangible-joint check below ties into the existing IS 803 Vent Sizing calculator (Appendix C) when a design falls outside the frangible criteria.
Identification
Research entries stay private to you for practice/testing. Switch to Official once this is a real design your company should see.
General Roof Requirements (§6.4.2)
Result
Minimum uniform live load, projected area1225 N/m² (125 kgf/m²)
Minimum roof plate thickness5 mm
Minimum structural member thickness4.5 mm
Frangible Roof-to-Shell Joint Check (§6.4.2.5)
Frangible if weld ≤5mm AND slope is 1:6 or flatter (ratio ≥6). Otherwise, emergency venting per Appendix C is required — see the IS 803 Vent Sizing calculator.
Result Not evaluated
Determination—
Supported Cone Roof — Rafter Spacing (§6.4.4)
Result
Maximum outer-ring rafter spacing (along circumference)2.0 m
Maximum inner-ring rafter spacing1.75 m
Tie rods between outer rafters—
Roof slope minimum 1 in 16 (§6.4.4.b). Rafters shall not be attached to roof plates (§6.4.2.3).
Self-Supporting Cone Roof (§6.4.5, §6.4.5.1)
Result Not evaluated
Angle check (≤37°, sinθ ≥0.165)—
Minimum roof plate thickness—
Required compression ring cross-sectional area—
Compression ring area (top angle + shell/roof plates within 16×t of attachment) required ≥ D²/(40 sinθ), in cm² with D in m.