Seismic Overturning & Anchorage

Site ground motion, base shear, overturning moment, and self-anchored/mechanically-anchored determination (API 650 §E.3–E.6)

◉ API 650 APPENDIX E (§E.3–E.6) STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL

⚠ Indicative tool only — seismic design is safety-critical. Every formula here was checked directly against the standard's page images (this was a scanned/OCR'd PDF; many equations came through as blank placeholders in the extracted text and had to be read from the actual pages). This tool covers §E.3–E.6: site ground motion, design loads, overturning moment, and the anchorage ratio / self-anchored determination. It does not cover §E.6.1.4 (dynamic liquid hoop stresses), §E.7 (freeboard/sloshing, detailing, piping flexibility, foundation design) — freeboard is planned as a follow-up calculator. Site classification (§E.4.4) is simplified to direct Site Class selection rather than full soil-profile averaging — use your geotechnical report's Site Class directly. This is not a substitute for a qualified structural/geotechnical engineer's seismic design.

Identification

Company

Tank ID

Location

Record Type

Research entries stay private to you for practice/testing. Switch to Official once this is a real design your company should see.

Site Ground Motion (§E.4)

Unit System

Seismic Use Group

Site Class

Anchorage Assumption to Check

S_S — Mapped MCE Ss (0.2s) %g, e.g. 0.75 for 75%g

S₁ — Mapped MCE S1 (1s) %g

S₀ Override %g (blank = 0.4×Ss)

T_L — Long-Period Transition sec

Q — MCE-to-Design Scaling

F_a (computed)

F_v (computed)

T_S = F_vS₁/(F_aS_S) (computed)

Site Class F requires a site-specific ground motion study (§E.4.2) — not computed here. F_a/F_v are linearly interpolated from Tables E-1/E-2, matching the standard's own tabulated breakpoints.

Tank Geometry & Weights

Diameter D m

Design Liquid Height H m

Design Specific Gravity G

Total Product Weight W_p N

Shell + Appurtenances Weight W_s N

Roof Weight W_r N

Bottom Weight W_f N (optional)

Roof Load on Shell w_rs N/m

Height to Shell CG X_s m

Height to Roof CG X_r m

Consider vertical seismic (A_v)

Anchorage Check Inputs (§E.6.2)

Annulus/Bottom Thickness t_a mm

Bottom Shell Course Thickness t_s mm

Annulus/Bottom Yield Strength F_y MPa

Shell Yield Strength F_ty MPa

Internal Pressure Uplift w_int N/m (0 for atmospheric)

Spectral Accelerations & Periods

Impulsive spectral acceleration A_i—

Convective period T_c—

Convective spectral acceleration A_c—

Effective Weights & Heights

Effective impulsive weight W_i—

Effective convective weight W_c—

X_i / X_c (ringwall moment arms)—

X_is / X_cs (slab moment arms)—

Base Shear & Overturning Moment

Impulsive / Convective base shear V_i / V_c—

Total design base shear V—

Ringwall moment M_rw—

Slab moment M_s—

Anchorage Ratio & Determination Not evaluated

w_t (shell + roof reaction per unit circumference)—

w_a (self-anchored resisting force, capped)—

Anchorage ratio J—

Table E-6 determination—

Shell Compression Check (§E.6.2.2) Not evaluated

Maximum longitudinal shell compression σ_c—

Allowable compressive stress F_C—

Mechanical Anchor Design Load (§E.6.2.1.2)

w_AB (design uplift per unit circumference)—

P_AB (design load per anchor)—

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