27.1. Mooring Loads

Based on this chapter you will understand the loads on a mooring system and how a design is performed. Some important considerations are given for the design of a mooring system.

Loads (actions) on a floating or submerged body can be classified as permanent, variable, environmental, or accidental.

Permanent / Variable Loads

• Hydrostatic loads: Weight and buoyancy forces acting on the structure.

• Ballast & variable weights: Changes in mass distribution due to ballast adjustments, operational payloads, or other variable loads.

Environmental Loads

• Wind loads: Including gusts and squalls acting on exposed surfaces.

• Current loads: Steady or varying currents applying forces along the hull or mooring lines.

• Wave loads:

  • First-order oscillatory forces.

  • Second-order drift forces due to sum and difference frequencies.

• Other phenomena: Potential ice loads, solitons, or extreme environmental events.

Accidental Loads

• Impact forces: From ships, submarines, or other floating objects.

• Accidental flooding/submergence: Rapid changes in buoyancy or weight.

• Loss of mooring line(s): Sudden redistribution of forces on remaining lines.

Response Characteristics

• Hydrostatic stiffness: Restoring forces resulting from buoyancy and weight distribution.

• Mooring stiffness and damping: Resistance and energy dissipation provided by connected mooring lines, risers, or cables.