Design Codes

AutoPIPE includes the following offshore design codes:

• B31.4 Offshore 2004, 2009, 2012, and 2016.
• B31.8 Offshore 2003, 2007, 2010, 2012, 2014, and 2016.
• CSA Z662 Chapter 11, Offshore 1999, 2007, 2011, and 2015.
• DNV-OS-F101 Offshore 1981, and 2012.
• DNVGL-ST-F101 Offshore 2017

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Code Calculations

Onshore piping code consider several stress categories:

• Hoop Stress (Circunferential Stress)
• Primary Stress (Sustained Stress)
• Secondary Stress (Thermal range stress)
• Occasional Stress
• Fatigue

To consider the effect of external pressure on subsea piping, some of the offshore codes calculate many more stress categories:

• Burst
• Buckling Local
• Buckling Propagation, and Buckling Combination
• ASD Check

AutoPIPE calculate all those stress categories to fully comply with the offshore codes.

Wave Loading

AutoPIPE includes the following wave loading theory:

• Airy wave theory (linear first order).
• Stokes’ wave theory (up to fifth order).
• Stream function wave theory (up to tenth order)
• Current (no wave theory).
• Buoyancy effects must be included separetely.
• Marine growth and current velocity can be entered at different depths.

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Wave theory

• Airy wave theory – small amplitude
• Stokes wave theory – intermediate and deep water
• Stream function wave theory – near breaking wave criteria
• Hydrodynamic forces:
• Inertia forces \(F_I = C_m \times \rho \times V \times \vec{u}\)
• Drag forces \(F_D = \frac{1}{2} C_d \times \rho \times A \times u \times | u |\)
• Lift forces \(F_L = \frac{1}{2} C_L \times \rho \times A \times u \times | u |\)
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Buoyancy

AutoPIPE calculate automatically the buoyancy force. Only the water level has to be set.

• AutoPIPE treats buoyant forces as a uniformly distributed load acting along the submerged length of pipe.
• Buoyancy forces are added to AutoPIPE gravity load case.
• End cap forces are considered by AutoPIPE for submerged pipes.
• Water surface elevation and other variables controlled through “Load > Buoyancy”.
• Suggested to have closely spaced nodes in the vicinity of water surface, preferably a node at water surface elevation.

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Risers

AutoPIPE can model the risers and the loads that apply to them, like difference in pressure inside/outside, waves, and support imposed displacements.

• AutoPIPE calculate the internal pressure using the know pressure at one point and the density of the fluid. AutoPIPE also calculate the external pressure based on the elevation of the sea level.
• Important to discretize the riser pipe to better capture wave loading, internal / external pressure difference.
• Riser clamp attachments can be simulated by connecting attaching guide supports connected to pipe and frame members (can be used to simulate platform movement).

Jacketed Pipes

Jacketed Pipes or Pipe Bundles are used to go from the seabed installations to the surface. The external pipe is used to support the external forces, as the waves and protect the process piping.

• Model pipes as different segments and different pipe IDs.
• Connection to the jacket pipe can be modelled by using guide supports connecting the two pipes.
• Different operating conditions can be defined for the different pipes within the jacket.
• Apply buoyancy or hydrodynamic data to the jacket pipe only.

Combined Models Structural Steel - Piping

AutoPIPE and STAAD.Pro has a two-way integration that allows the structural model to be imported and connected to the piping. The piping model and the loads calculated can be imported into STAAD.Pro.

The combined model uses the combined flexibility and the displacement at the support are imposed automatically into the piping model.

• Export structural model from STAAD to be imported to AutoPIPE.
• Piping support loads can be exported to STAAD.Pro.
• Update dimensions for piping according to changes made in frame.
• Impact from high piping loads can be quickly seen on the structural model.