a. Piping code = General
b. Pipe code to calc SIF = BS 806
Suggest the following options under Tools> Model Options > Result ,A. Direct Shear (N/R/A) = A (CSA-Z662 and BS8010)Note: Autopipe always considers axial and torsional stress for the General piping code and to add Direct shear stress for codes abov
B. Total stress(Oct/Max)" = O, Von Mises is required for the British code BS8010 i.e equivalent stress and CSA-Z662
C. Shear Stress : Offshore codes do not have allowable for shear stress only. Default = 0.6
i. BS8010:1993 - Torsional + Direct Shear (Tangential)
ii. CSA-Z662: 1999 - Torsional + Direct Shear (Tangential shear). Note: Torsional stress cannot be disabled for General pipe code hence is always consider.
D. Hoop Safety Factor, Long Safey Factor, Shear Allow.Total Allow.
Notes:
The following typical load cases are analyzed. Where U1 and U2 and two wave cases and T1 - Tx is thermal case.
NOTE: Pressure analysis is considered since offshore piping systems can have very high pressure e.g 2000 psi
Where GR+P1 and GRT1P1 are functional load combinations and GRT1P1+U1 is a functional + environmental load combination under the occasional category with K-factor = 1.33 (Tools> Combinations> .
Note: under Tools> Model Options> Result Options dialog, "Apply all K-factors" = checked ON (see image above).
To more accurately calculate the axial cap pressure force Use “Tools/code combinations/longitudinal pressure “ and change the basis for longitudinal pressure stress = AxF/area i.e for thick pipe calculation instead of PD/4t and “include rigorous pressure” = Y to include axial stress due to pressure.
Ignore Maximum Shear Stress Ratio the System Summary report
The allowable stress for the CSA-Z662 functional + environmental load combination e.g GrT1P1+U1 will be based on the conservative riser value of 0.60 for functional load combinations therefore if any overstress in the functional + environmental load combinations manually assess if acceptable by multiplying the allowable by 0.8/0.6 (riser) = 1.33 or 1.0/0.6 for seabed piping using Pre-Autopipe 6.3 versions.
In Autopipe v6.3 , under Result Options dialog "Apply all K-factors" = checked and define functional + environmental combinations as shown in Load combinations section above.
Select a point on the riser and evaluate functional and environmental combinations e.g. Gr+P1+T1 & GR+T1+P1+U1 respectively
Evaluate axial stress = 1/2 x(sum of the longitudinal Max and min stresses)
Stress convention : +ve = tension, -ve = compression.
Modeling Approaches
Bentley AutoPIPE