Dear all,
I am trying to carry out a comparison between hand calculation and Caesar computed results. I have certain doubts to clear.
I have considered : Simply supported beam with no external force, no insulation. Code : B31.3, Pipe = 4” Wall Thk = 6.0198, Temp Design = 65 deg & Press. Design = 14.36 bar g, Length = 1000mm(Node 10-15 = 500mm , 15-25 500mm), Fluid density = 670kg/m3

A)LOADCASE 4 (SUS) W

Highest Stresses: ( KPa )
Ratio (%): 0.5 @Node 15
Code Stress: 641.6 Allowable Stress: 137895.1
Axial Stress: 0.0 @Node 15
Bending Stress: 641.6 @Node 15
Torsion Stress: 0.0 @Node 15
Hoop Stress: 0.0 @Node 15
Max Stress Intensity: 641.6 @Node 15

B)LOADCASE 7 (SUS) P1

Highest Stresses: ( KPa )
Ratio (%): 5.8 @Node 15
Code Stress: 8020.3 Allowable Stress: 137895.1
Axial Stress: 8020.3 @Node 15
Bending Stress: 0.0 @Node 15
Torsion Stress: 0.0 @Node 15
Hoop Stress: 16729.5 @Node 15
Max Stress Intensity: 18914.1 @Node 15

C)LOADCASE 8 (SUS) W+P1

Highest Stresses: ( KPa )
Ratio (%): 6.3 @Node 15
Code Stress: 8662.0 Allowable Stress: 137895.1
Axial Stress: 8020.3 @Node 15
Bending Stress: 641.6 @Node 15
Torsion Stress: 0.0 @Node 15
Hoop Stress: 16729.5 @Node 15
Max Stress Intensity: 18914.1 @Node 15


1) The axial stress mentioned in all load case above is the stress due to longitudinal pressure force alone. By the Caesar default equation, the results found to match. As per B31.3, axial force due to sustained structural loads (F/A) has to be also added to compute the code stress. But none of the case above, F/A term has been considered. From Configuration >>SIF& Stress>> changing “Add F/A in stress” to ‘default/yes/no’ make no difference in the axial stress above. Please clarify !!!!

2) Also what is the purpose of “Use PD/4t” in the configuration settings ? Does it mean that Caesar will default to this eq. for calculation of axial stress when turned ‘ON’ ? If yes, turning it ON doesn’t change the computed axial stress above…


3) As per code para 304.1.2 - eq. (3a), D = Outside diameter of the pipe. Why does Caesar default to ‘hoop stress calculation based on ID’ for B31.3?

http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=58570



But here in all the above load cases, for calculation of Hoop stress, ID & nominal thickness less allowances are used (cross checked using manual calculation)



Please clarify my doubts.
Many thanks in advance