Load Cases with Pitch and Roll - CAESAR II - Help

CAESAR II Users Guide (2019 Service Pack 1)

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English
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CAESAR II
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CAESAR II Version
11.0 (2019)

There is often platform movement, or relative movement, between two platforms with inter-connected piping, in an offshore piping system. This also applies to FSPO and other shipboard piping systems. Apply the pitch and roll displacements to CNodes on each affected restraint. Use displacement vectors not already in use to describe thermal displacement boundary conditions. There is usually a + displacement and a - displacement to describe the peak pitch and roll conditions. Look at the state of the platform at its peaks to determine the worst two conditions for relative displacement between piping separated by the largest distance along the line of wave travel. D3 and D4 describe two peak pitch conditions. D1 is a thermal displacement.

L1

W+T1+D1+D3+P1

(OPE)

L2

W+T1+D1+D4+P1

(OPE)

L3

W+P1

(SUS)

L4

L1-L3

(EXP) *

L5

L2-L3

(EXP) *

* Use the algebraic combination method in the Static Analysis - Load Case Editor.

It is likely that you will want to perform a fatigue analysis because of the large number of displacement cycles common in pitch and roll situations. Select the appropriate fatigue curve on the first piping input under the Allowable Stress area on the Classic Piping Input dialog box. Add the following cases to the previous example. Enter the number of cycles for each pitch condition for fatigue stress type (FAT).

L6

L1-L3

(FAT)

21000000

L7

L2-L3

(FAT)

21000000

The 21000000 represents 21 million load cycles during the life of the piping system. Use the number of cycles that you would expect to occur during the life of such a storm for large displacements, such as those that occur during a 1-year, 30-year, or 100-year event. Multiply this number by the number storms likely to happen during the lifetime of the piping system.