Convective lateral force coefficient and sloshing period for storage tanks (BS EN 14015:2004, Annex G.2.3)
◉ BS EN 14015:2004 ANNEX G.2.3 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only, and deliberately narrow in scope. Annex G opens by stating it is based on API 650 Appendix E, with zone coefficients "modified to lateral force coefficients expressed as a ratio of the acceleration due to gravity." Its overturning-moment formula and effective-mass charts (Figures G.1–G.2) are the same underlying Housner-derived methodology already built into the existing Seismic Freeboard calculator — both trace back to the same ERDA TID-7024 source, per the standard's own footnote — so this tool deliberately does NOT duplicate that. What's genuinely distinct to this annex is the G1→G2 lateral force coefficient relationship below, verified directly against the page images (including a continuity check across the formula's period-based branch, which came out consistent to 5 decimal places).
Identification
Research entries stay private to you for practice/testing. Switch to Official once this is a real design your company should see.
Site Amplification Factor (Table G.1)
Where the soil profile isn't known in sufficient detail, Type C shall be assumed (the standard's own conservative default).
Result
Site amplification factor j—
First-Mode Sloshing Period (Annex G, Ts formula)
Ts = 1.8 × Ks × √D. Figure G.3 is a graph, not a table — read Ks off the chart for your tank's D/HT ratio and enter it manually.
Result
First-mode sloshing period Ts—
Lateral Force Coefficients (§G.2.3.1–.2, Eq.G.2–G.3)
G1 is specified by the purchaser directly from seismology records for the site, as a ratio of the acceleration due to gravity — not computed here. G2 = 1.25G1j/Ts when Ts≤4.5s, or 5.625G1j/Ts² when Ts>4.5s.
Result
Governing branch—
Convective lateral force coefficient G2—
G1 and G2 feed into the overturning moment formula (Eq.G.1), which uses the same effective-mass/centroid charts (Figures G.1–G.2) as the existing API 650-based Seismic Freeboard calculator — use that tool for the overturning moment and freeboard results once you have G1 and G2 from here.