Question
How AutoPIPE Vessel calculates Longitudinal stress & General primary membrane stress intensity?
Formulas used are not found in EN13445, What is the basis of the formulas used in the calculations?
Answer
Longitudinal stresses are checked as per the code requirements given in the British standard PD 5500 (G.3.3-5) and (G.3.3-6)
Formula to calculate the General primary membrane stress intensity come from British standard PD 5500 B.4.
Justification:
Initially, only BS5500 provided a method for verifying saddles; this is the origin of the calculations performed by APV. Subsequently, other codes added verifications based on the same principles, sometimes with improvements.
This is the case for stress between two saddles (mid-span). The EN and AD S3/2 added a coefficient (K12 in EN, K14 in AD S3/2) increasing the bending moment to account for the non-conservation of the cross-section of the equivalent beam. APV chose to adopt a method common to all codes, incorporating improvements from each. This is also the reason why a distinction is made between the tension side and the compression side, as in the PD5500 and CODAP.
This is the case for stress between two saddles (mid-span). The EN and AD S3/2 added a coefficient (K12 in EN, K14 in AD S3/2) increasing the bending moment to account for the non-conservation of the cross-section of the equivalent beam. APV chose to adopt a method common to all codes, incorporating improvements from each. This is also the reason why a distinction is made between the tension side and the compression side, as in the PD5500 and CODAP.
Regarding the general primary membrane stress intensity, there is a problem in the literal equation of the report, we apply PD5500 B.4 Note 2 (no torque):
