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.
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.