Problem:
How does AutoPIPE Vessel calculates the Allowable Compressive Stress (fc) as per CODAP Div. 2?
Solution:
Users may notice that the allowable compressive stress (fc) reported by AutoPIPE Vessel differs from the nominal allowable stress (f) and may require clarification regarding the governing equation used by the software.
For cylindrical shells designed according to CODAP Division 2, AutoPIPE Vessel evaluates the allowable longitudinal compressive stress (fc) using the buckling limitation specified in CODAP Div. 2, Clause C9.1.4.5(a).
Compressive meridional stress must satisfy:
Where:
-
-
- fc = Allowable compressive stress (MPa)
- K = Buckling coefficient
- e = Shell nominal thickness (mm)
- Dm = Mean shell diameter (mm)
- E = Modulus of elasticity (MPa)
-
As shown in the results report:
Maximum longitudinal compressive stress: σz < 0 ⇒ |σz| shall be ≤ MIN(fc ; ft)
Example:
In this case (Erected, New Inertia, New weight), You can see AutoPIPE Vessel report value is matching with the manual calculations.
AutoPIPE Vessel Report:
Manual Calculations:
| Parameter | Value |
|---|---|
| K | 1.35 |
| e | 25 mm |
| E | 212000 MPa |
| Dm | 6225 mm |
| fc | 143.67 MPa |