Comments, Questions, and Answers

Q1. How is Buoyancy added in AutoPIPE?

Answer: In AutoPIPE buoyancy weight is applied in GR case. It has both longitudinal and transverse components. When the pipe is vertical, difference in pressure cap forces is the same as buoyancy load and the transverse buoyancy is zero. When the pipe is horizontal, the cap forces from external hydrostatic load adds longitudinal stress and associated movements in addition to non zero transverse (vertical) buoyancy load.

Q2. Is Pipe insulation and Cladding accounted fro in bouyancy?

Answer: Form the online help:

Clad thickness: For wind loading, hydrotest, buoyancy and wave loading, the total diameter of pipe includes the cladding thickness.

Insulation thickness: The insulation thickness is also used to calculate the surface area of the pipe for wind loads and buoyancy effects.

Q3. How do I know if Buoyancy loads are being applied to the pipe?

Answer: At this time there is no single reported value in AutoPIPE for the total Buoyancy at each node point or for the entire model.

Workaround, must have 2 identical models, where the only differency is in one model, apply Load> Buoyancy as required, and then compare the results of all the vertical support loads under GR load case. The difference between the total vertical support values between both models is the buoyancy load applied to the piping.

Remember All points with a vertical coordinate value less than the "Water surface elevation" value specified on the Load> Buoyancy dialog will be considered submerged (buoyancy load is applied). Piping above this value will be considered above water and NO buoyancy will be applied.

In addition, confirm Segment tab on the input grid, "Apply Buoyancy" column for check boxes where Buoyancy load  is to be consideration for above / below "Water surface elevation" value:

Q4. Can you please explain the difference if any in how hydrodynamic loads are applied to both pipe sections utilising soil springs and pipe sections utilising v-stop supports.

Answer: In short there is not much difference. The pipe is supported by either soil springs or V-stop supports. The buoyancy load is another load case applied to the pipe as with any other load case (i.e. Wind). As you know buoyance load  is applied with the gravity (GR) load case (combined total of dead weight and bouyancy weight). Also becuase of the general nature of the different supports, pipe movement may be restricted more so by a given soil springs than a V-stop. Regardless, when GR is evaluated the pipe will move as the supports will allow.     

See Also

Bentley AutoPIPE

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

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