Offshore Structural Engineering Tools

Disclaimer: These tools are for preliminary estimation only. Always verify results with qualified engineers and the applicable project design codes, including API RP 2A-WSD and ISO 19902. Do not use for final design without independent verification.

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Morison Wave Force

Drag + inertia forces on cylindrical members (API RP 2A)

Env. Loads

Diameter D (m)

Water Depth d (m)

Wave Height H (m)

Wave Period T (s)

Drag Coeff Cd

Inertia Coeff Cm

Enter wave conditions and click Calculate

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Wind Load — Topsides & Decks

Wind force on offshore structures (API RP 2A-WSD §2.3)

Env. Loads

Design Wind Speed V (m/s, 1-hr mean)

Projected Area A (m²)

Shape / Drag Factor Cs

Height Factor Ch (elevation above MSL)

Enter wind parameters and click Calculate

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Current & Wind Drag — Members

Drag force on cylindrical members (Moody / DNVGL)

Env. Loads

Load Type

Velocity (m/s)

Diameter (m)

Member Length (m)

Drag Coefficient Cd

Enter flow parameters and click Calculate

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Pipeline / Spool Buoyancy

Net buoyancy and submerged weight check

Pipeline

Outer Diameter OD (mm)

Wall Thickness WT (mm)

Spool / Pipe Length (m)

Content

Enter pipe dimensions and content type

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Pipeline Free Span Natural Frequency

Pinned-span first-mode natural frequency estimate

Pipeline

Pipe Outer Diameter (m)

Free Span Length (m)

Effective Tension (kN)

Pipe wall thickness (m)

Effective dynamic mass, including contents and added mass (kg/m)

Enter span geometry and mass

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Mooring Line Tension

Catenary mooring — horizontal restoring force

Marine

Submerged Line Weight w (kN/m)

Water Depth d (m)

Total Line Length L (m)

Horizontal Tension H (kN, at fairlead)

Enter catenary mooring parameters

Jacket Platform Design Guide → Grating Calculator & Offshore Standards →

Offshore Structural Engineering — Calculation Methodology

The available tools provide indicative arithmetic for wave force, wind load, member drag, pipeline buoyancy, free-span natural frequency and mooring tension. They do not establish code compliance. Check assumptions and results against the current applicable project standard, such as API RP 2A-WSD or ISO 19902 for fixed offshore structures.

Morison Wave Force Equation

Wave forces on slender cylindrical members (tubular jacket legs and braces) are calculated using the Morison equation:

F = C_M × ρ × (π/4) × D² × a + C_D × (ρ/2) × D × u|u|

Where F is the total wave force per unit length (N/m), C_M is the inertia (mass) coefficient (typically 2.0 for smooth cylinders per API RP 2A), C_D is the drag coefficient (typically 0.65–1.05 depending on roughness and Reynolds number), ρ is seawater density (1025 kg/m³), D is the outer diameter of the member (m), a is the wave particle acceleration (m/s²), and u is the wave particle velocity (m/s). The first term represents inertia (mass acceleration) force; the second represents drag force.