External pressure consideration in deep offshore - True wall force

"Akin Akangbe" wrote:

Regarding your response to previous discussion on bentley.autopipe

Subject: Re: Hydrostatic Loading;

Can you then confirm that AutoPIPE is not suitable for deep offshore analysis as regard to calculating true pipe wall force which will take into consideration the end cap effect and external pressure.

  • "Karim Rinawi [Bentley]" wrote in message news:4889542b@news.prod-bent.dmz...

    AutoPIPE does apply the axial force created by hydrostatic forces. This is included in the buoyancy for the GR load case.

    AutoPIPE does not handle negative pressure loading (or vacuum) at this time. External pressure can be approximately accounted for by subtracting it from internal design pressure.

    AutoPIPE has been successfully deployed on many deep water riser analyses. Usually the pipe is close to vertical or lies on the sea bed. Stinger pipes cannot be analyzed in AutoPIPE as we do not handle catenary action.


    Karim

  • This is a previous

    FAQ #36 found in the AutoPIPE online help

    Question 36: How do I calculate the DNV 2000 tension terms?

    Answer: In accordance with DNV 2000, AutoPIPE currently can output the following Local Forces and Moments results:

    Note: Local forces convention -ve = tension +ve = compression With buoyancy defined under Load/buoyancy the hydrostatic forces are calculated and automatically included in the GR case.

    1. GR = N + PeAe
    2. P1 = internal pressure forces in pipe wall not including PiAi (capped pressure term).
    3. GR + P1- PiAi = S = N + PeAe - PiAi

    Since the sign conventions for
    S (Effective axial force) ,
    N (True axial force in the pipe wall)
    PeAe is consistent with respect to tension or compression i.e signs are automatically calculated by the program and included in the GR and P1 load cases.

    Mark Upston