Floating Dock Pontoon Sizing And Uls Analysis

Core Workflow

1. Sizing Calculation:

   • Calculate the required submerged volume to support the TGL when pontoons are 100% submerged.
   • Determine the total pontoon volume required to achieve the target submergence (50-70% heuristic) under Dead Load only.
   • Calculate cross-sectional area ($A_{gross}$) based on total volume and pontoon length.
   • Calculate diameter ($D$) using $D = 2 \times \sqrt{A_{gross} / \pi}$.
   • Verify the submergence level percentage under dead load for the calculated diameter.

2. ULS: Buoyancy Check at Max Gravity Load:

   • Verify buoyancy capacity against the combined Dead Load and Live Load.

3. ULS: Lateral Loads (Wind, Berthing) & Mooring Piles:

   • Calculate Wind Load based on pressure and exposed surface area.
   • Calculate Berthing Load ($F_b$) using energy and deflection.
   • Pile Analysis:
     • Calculate geometric properties for circular pile sections: Moment of Inertia $I = \frac{\pi d^4}{64}$ and Section Modulus $Z = \frac{I}{c}$.
     • Calculate Bending Moment at the pile base: $M = R \times L$ (Reaction force x Effective Length).
     • Calculate Bending Stress using Section Modulus: $\sigma = \frac{M}{Z}$. Compare to material Yield Stress ($F_y$).
     • Calculate lateral deflection at the pile head: $\delta = \frac{F L^3}{3 E I}$. Compare against allowable limits (e.g., diameter/150).
   • Pontoon Check: Check pontoons for structural adequacy (stress and deflection) against the applied lateral loads.

4. ULS: Longitudinal Flexure (Wave Action):

   • In the presence of waves, find an equivalent span (or use a refined method) to check longitudinal flexure ($M_f, V_f$).
   • Specific Loading Logic: Assume buoyancy acts only over parts of the pontoons near wave crests (high water surface), while dock dead and live loads span over the wave trough.

5. SLS: Vibration/Dock Movement:

   • Consider vibration and dock movement in the analysis.

Anti-Patterns

• Do not add wind load to the gravity load for buoyancy sizing.
• Do not skip the wave-induced flexure analysis or simplify it to just static buoyancy.
• Do not assume safety factors unless explicitly provided.
• Do not ignore the specific shear area assumption ($0.5 \times A_{gross}$).
• Do not provide a generic list of steps without numerical demonstration.
• Do not ignore the cantilever assumption for mooring piles.
• Do not use the moment of inertia directly for stress without the distance to the neutral axis (use Section Modulus Z).

Triggers

• calculate pontoon pipe diameter
• size PE4710 pontoons for floating dock
• check floating dock ULS
• berthing load calculation
• mooring pile check
• analyze floating dock structure