Dome shell buckling allowable load, panel design loads, and fastener combined-stress check (ANSI/AWWA D108-19, §5)
◉ ANSI/AWWA D108-19 §5 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only, and genuinely new territory for this project. AWWA D108 covers aluminum geodesic/triangulated-frame dome roofs — a completely different roof type and material from every steel cone/dome roof built so far (API 650, IS 803, EN 14015). Written primarily for water storage tanks, but aluminum dome covers are also common on petroleum tanks, especially as internal covers over floating roofs. Verified directly against this edition's page images.
⚠ Critical discrepancy between the US and metric versions of Eq 5-1 — verify against your own copy before use. The standard presents these as "equivalent" equations, but they are not simple unit conversions of each other: the US customary formula uses (Ix×A)½ (multiplication), while the metric formula (§5.5, Sec. 5.5 table) uses (Ix/A)½ (division) — confirmed by directly viewing both page images, not a transcription error on our end. For representative strut dimensions, these two forms produce results differing by roughly 600× when compared on a consistent basis. (Ix/A)½ is the classical radius of gyration, a standard structural quantity, which may suggest the metric form is the physically intended one — but we are not making that call for you. Both are implemented below exactly as printed; pick a unit system and it uses that unit's own printed formula, not a cross-converted one.
Identification
Research entries stay private to you for practice/testing. Switch to Official once this is a real design your company should see.
Dome Physical Characteristics (§7)
Unless otherwise specified, maximum dome spherical radius = 1.4×D; minimum = 0.7×D. Uses the same unit system selected below.
Result Not evaluated
Permitted radius range—
Proposed R vs. range—
Allowable Dome Shell Buckling Load (§5.4.1, Eq 5-1)
US: w = 2,258×10⁶(IxA)½/[(SF)R²L]. SI: w = 108.1(Ix/A)½/[(SF)R²L], as printed — see the discrepancy note above.
Unbalanced loading: reduce the live load by 50% over one-half the dome. Panel design load (does not act simultaneously with other design loads): Load Case 1 — two 250 lb (113 kg) loads concentrated on two separate 1 ft² (0.093 m²) areas of any aluminum panel; Load Case 2 — a 60 psf (293 kg/m²) uniform load distributed over the total panel area.
Load combinations to consider: (1) dead load; (2) dead + uniform live; (3) dead + unbalanced live; (4) dead + wind; (5) dead + uniform live + wind; (6) dead + unbalanced live + wind; (7) dead + seismic.
Fastener Combined Shear & Tension (§5.4.3)
ft/Ft + fv/Fv ≤ 1.3. Doesn't apply to post-set concrete anchors (governed by ACI 318 instead). Grade 18-8/18-10 stainless fasteners for minor connections <5/16in (8mm): allowable shear 12,000 psi (85 MPa), allowable tension 18,000 psi (125 MPa).