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