Hi,

In subsea applications we need to check external pressure collpase calculations. I could input negative pressure in Caesar version 5.0. But this tool is not available in 5.1 or 5.2.

Can anyone advice me how to check for external pressure? Here we are talking about water depth in the range of 1300 m.
This is different from burried piping.

Regards,
Kaustubh

CAESAR II does not perform buckling or collapse analysis. Pressure is used only for:

1) the thrust force on expansion joints
2) the longitudinal pressure stress component of the code stres calculation.

So if you input a negative pressure, the force on the expansion joint will be compressive instead of tensile. The absolute value of the pressure is used in the longitudinal pressure stress computation.

Negative pressures were prevented in 5.10 and 5.20 because too many users incorrectly assumed the software was performing a buckling or collapse check it's not! With Version 5.30 we removed this restriction, you can input a negative pressure, and the software will work as in 5.00 and earlier.

Note, CAESAR II uses the 3D beam element. This element is not sufficient to perform a buckling or collapse analysis.

Richard, I would like to add a comment on this discussion.

I am analyzing a subsea structure, and the external water pressure should be taken into account while calculating the hoop stress.

As discussed above, we can input the difference between the internal and external pressure in the Pressure.

Alternately, according to my colleagues, we can define the global coordinates at the beginning element. And define wave in the Static Load Case Editor.

Here is the interesting part, if we only define the global coordinates, the hoop stress calculation does take the water pressure in. This only works when we define both.

I am guessing that CAESAR II treats the structure as submerged only if the wave data is difined.

Is that right?

Correct. If the system is submerged, CAESAR II will determine the external pressure at the node's depth to implement the (Pe - Pi) term in the hoop equation.