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AutoPIPE Wiki 13. How are the RAHL values calculated? When do the sliding saddles start to move in AutoPIPE Vessel?
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              • 13. How are the RAHL values calculated? When do the sliding saddles start to move in AutoPIPE Vessel?
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    13. How are the RAHL values calculated? When do the sliding saddles start to move in AutoPIPE Vessel?

    Applies To
    Product(s): AutoPIPE Vessel
    Version(s): V8i 
    Area: Calculations
    Original Author: Bentley Technical Support Group
    Date Logged
    & Current Version
    Aug. 2015
    33.02.02.04

    Problem:

    When do the sliding saddles start to move in AutoPIPE Vessel?

    Answer:

    It depends of the friction factor inputted in the dialog of the saddles between the sliding saddles and the concrete or the plate under the sliding saddles.

    A small friction factor value indicates that a PTFE plate or in some cases rolling bars have been installed.

    The values of the longitudinal loads (RaHL) are calculated as follow:

     

    No.

    Support saddles Location (mm) Stiffness
    (daN/mm)

    Vertical

    Horizontal

    Combined

    Reactions
    (daN)

    Shear Loads
    (daN)

    Bending moments
    (daN∙m)

    Reactions
    Transverse
    (daN)

    Shear Loads
    (daN)

    Bending moments
    (daN∙m)

    Reactions
    Longitudinal
    (daN)

    Reactions
    (daN)

    Shear Loads
    (daN)

    Bending moments
    (daN∙m)

    1

    500.0

    2,716.2

    -324.1
    2,392.2

    -144.2
    -2,424.7

    0.0

    0.0

    0.0

    2,402.7

    2,716.2

    -324.1
    2,392.2

    -144.2
    -2,424.7

    2

    4,500.0

    4,190.7

    -1,623.1
    2,567.7

    -2,245.8
    -697.1

    0.0

    0.0

    0.0

    -1,629.2

    4,190.7

    -1,623.1
    2,567.7

    -2,245.8
    -697.1

    3

    8,500.0

    2,057.6

    -1,433.9
    623.8

    -1,134.0
    -744.0

    0.0

    0.0

    0.0

    -521.1

    2,057.6

    -1,433.9
    623.8

    -1,134.0
    -744.0

    4

    11,500.0

    673.9

    -349.8
    324.1

    -333.5
    -144.2

    0.0

    0.0

    0.0

    -252.4

    673.9

    -349.8
    324.1

    -333.5
    -144.2


    The fixed saddle is located in this example on the left hand.

    How are the RaHL values calculated?

    Run the model with a friction factor equal to 0 and you will obtain the values of vertical reaction loads used for the calculation of RaHL (as shown here after):

     

    No.

    Support saddles Location (mm) Stiffness
    (daN/mm)

    Vertical

    Horizontal

    Combined

    Reactions
    (daN)

    Shear Loads
    (daN)

    Bending moments
    (daN∙m)

    Reactions
    Transverse
    (daN)

    Shear Loads
    (daN)

    Bending moments
    (daN∙m)

    Reactions
    Longitudinal
    (daN)

    Reactions
    (daN)

    Shear Loads
    (daN)

    Bending moments
    (daN∙m)

    1

    500.0

    2,162.0

    -324.1
    1,837.9

    -144.5

    0.0

    0.0

    0.0

    0.0

    2,162.0

    -324.1
    1,837.9

    -144.5

    2

    4,500.0

    5,253.1

    -2,177.3
    3,075.8

    -2,181.7

    0.0

    0.0

    0.0

    0.0

    5,253.1

    -2,177.3
    3,075.8

    -2,181.7

    3

    8,500.0

    1,559.4

    -925.8
    633.7

    -585.1

    0.0

    0.0

    0.0

    0.0

    1,559.4

    -925.8
    633.7

    -585.1

    4

    11,500.0

    664.0

    -339.9
    324.1

    -144.5

    0.0

    0.0

    0.0

    0.0

    664.0

    -339.9
    324.1

    -144.5

     

    In this example, the mass of the each saddle is 181 kg (177.4 daN).

    The friction factor is equal to 0.3

    The loads on the sliding saddles are equal to:

    W2ini = 5253.1 + 177.4 =  5430.5 daN        -->           RaHL2 = 5430.5 x 0.3 = 1629.2 daN

    W3ini = 1559.4 + 177.4 =  1736.8 daN        -->           RaHL3 = 1736.8 x 0.3 = 521.1 daN

    W4ini = 664 + 177.4 =  841.4 daN                -->           RaHL4 = 841.4 x 0.3 = 252.4 daN

    The sign is –ve for these loads.

    The system is on equilibrium -->  Sumation of RaHL = 0

    The load on the fixed saddle is equal to:                RaHL1 = 1629.2 + 521.1 + 252.4 = 2402.7 daN

    When the longitudinal loads exist, the vertical loads are modified. These modified values are due to the moments 

    See Also

    AutoPIPE Vessel FAQ

    • AutoPIPE Vessel
    • saddles
    • Calculation
    • Loads
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    • JamieP Created by Bentley Colleague JamieP
    • When: Wed, Aug 26 2020 9:44 AM
    • Tanaji Gaikwad Last revision by Bentley Colleague Tanaji Gaikwad
    • When: Wed, Aug 2 2023 6:55 AM
    • Revisions: 3
    • Comments: 0
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