Dear All,

How CAESAR II is calculating the longitudinal stress for B 31.8 Code 2012.

As per code, Para 833.3 Summation of longitudinal Stress in Restrained Pipe

The net longitudinal stresses in restrained pipe are

SL = SP+ST+SX+SB.

Now As per code, Para 833.4 Combined Stress for Restrained Pipe,

The combined biaxial stress state of the pipeline in the operating mode is evaluated using the calculation
in either (1) or (2) below:

(1) SH - SL
(2) SL2- SL*SH- SH2

It means that if I am subtracting hoop stress from equation (1) I will get value of SL.

If I solve the equation (2) I will get the SL.

But these results are not matching with CAESAR II.

Can anyone clarify this?

(1) & (2) are separate stress calculations - (1) is stress intensity (Tresca or maximum shearing stress theory) and (2) is octahedral shearing stress (von Mises or equivalent stress theory)

CAESAR II will use (1) if your configuration setting for "Yield Stress Criterion" is "Max 3D Shear". CAESAR II will use (2) if your configuration setting for "Yield Stress Criterion" is "von Mises".

Only one of those two equations should produce your reported stress.