Case Study
Tank Shell & Roof FEA Verification — Wind & Seismic Load Analysis
FEA Analysis — Storage TankConfidential Details Removed
Problem / Requirement
A large-diameter floating-roof tank required verification beyond the prescriptive API 650 shell thickness formula because the diameter-to-height ratio fell outside standard applicability limits. The client's third-party inspector requested an FEA-backed report confirming the shell would not buckle under design wind speed and that the floating roof pontoon remained structurally adequate under combined hydrostatic and seismic sloshing loads.
Engineering Scope
Development of a detailed axisymmetric and 3-D FEA shell model from fabrication drawings
Application of hydrostatic pressure, wind pressure profile per ASCE 7 and internal vacuum loading cases
Linear buckling (eigenvalue) analysis to determine critical wind speed and safety factor against shell buckling
Non-linear post-buckling analysis to confirm load redistribution behaviour under extreme wind
Seismic sloshing load derivation per API 650 Annex E and application to floating roof pontoon
Stress linearisation across pontoon deck, rim plate and drainage system connection nodes
Weld joint stress and fatigue screening at critical pontoon-to-deck intersections
Preparation of FEA report with acceptance criteria, contour plots and pass/fail summary
Deliverables
FEA Model Description and Validation ReportShell Buckling Analysis Report — Wind LoadFloating Roof Pontoon Stress Analysis ReportSeismic Sloshing Load Calculation SheetFEA Contour Plot Pack (Stress, Displacement, Buckling Modes)Acceptance Criteria Compliance Summary Table
Client Value Delivered
FEA confirmed shell integrity at 160 km/h design wind, giving the client confidence ahead of the third-party audit
Buckling safety factor of 3.2 demonstrated — no stiffener rings required, saving material and fabrication cost
Floating roof pontoon stress results were below yield at all load combinations, avoiding costly redesign
Structured report with explicit acceptance criteria cross-references satisfied the inspector's requirements on first submission
Sloshing freeboard check confirmed existing tank height was adequate, eliminating the need for raised pontoon guides
Standards Referenced
API 650 (12th Ed.)API 650 Annex EAPI 650 Annex FASCE 7-22ASME BPVC Sec. VIII Div. 2 (stress limits)EN 1993-1-6 (shell buckling guidance)
Software Used
ANSYS Mechanical 2024 R1ANSYS WorkbenchTANK (Intergraph) — baseline checkMicrosoft Excel (load derivation)AutoCAD 2024 (geometry reference)
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