I am working on a system that has a composite material in it. Part FRP and part metallic.
It has come to my notice that there are high horizontal forces on anchors even in Sustained case. This force then adds on to the thermal forces and shows up a higher value in Operating case.Does Caesar consider pipe expansion in Sustained case for FRP pipes causing horizontal force in Sustained.
I have input all data that are required under ISO 14692 in Allowable Stresses.Similarly inputs as required in CFG file and Special Execution Parameters are used.

I tried lowering the pressure value in Caesar.With low pressures the anchor forces remain the same , thus eliminating doubts on Bourdon effect.

Are we missing something in the input.If this is usual behaviour,then is there a work around this issue.

Thanks in advance.

To my knowledge, not typically. You can enact the bourdon effect, but my understanding is that will only impact elbows.

Your inquiry is unclear a little bit, meaning that your scope or design problem are not clearly specified...

If you are interested in a realistic evaluation of pipe support (e.g. anchoring or line-stop) loading, then yes, Bourdon effect is mandatory to be considered...but it should anyway be automatically enabled on FRP/GRP pipe stress analysis. Other unclear matters I do not see here, pipe supports loads are not correlated with Code stress qualification. If you get high axial loads due to pressure load, that is!...you need to cope with this effect and proceed to pipe supports design accordingly.

If you are interested in Code stress qualification, then it may happen that axial/longitudinal deflection of the pipe due to pressure elongation effect to induce subsequent high bending stresses in the connected branched piping, for instance...
In such case, I'm afraid you cannot treat such stresses as Operating ones, to increase the partial load factor from 0.67 to 0.83, because ISO 14692 (like any other GRP/FRP piping standard/code) does not use the Effective Displacement Stress Range (SE) vs. Allowable Displacement Stress Range (SA) check criterion, like B31 Codes. Local yielding and bending stress self-limitation ARE NOT APPLICABLE to GRP/FRP piping. Therefore, you need to consider ALL the stress types induced by pressure+weight load effect as SUSTAINED stresses and to check them against the lowest allowable limit (0.67 value of partial load factor).
When you analyze Pressure + Weight + Thermal Expansion cumulated load, then yes, you deal with Operating case and you may increase the partial load factor from 0.67 to 0.83.

Regards,

CAESAR II will automatically include axial pressure strain for models containing FRP material.
For another method of diagnosis, I suggest you run a copy of your model that has your FRP material replaced with a metal. If the high axial terms disappear, I would believe "Bourdon" IS the source of your load.

Let us know what you find...

Hi again Manoj,

One more suggestion: In Configuration/FRP Properties spreadsheet, try to change the "BS 7159 Pressure Stiffening" parameter from "Design_Strain" default value to "Actual_Pressure" value, which is actually compliant with ISO 14692-3 analysis basis and definitely much more realistic for FRP/GRP piping actual behavior simulation.

This parameter affects how are calculated elbows' flexibility factors. Increasing pressure value, elbows flexbility factor decreases so that elbows become more rigid. The SIFs are reduced accordingly, but this is not relevant for your support loading problem.

Please note that the default "Design_Strain" parameter "instructs" Caesar II to consider that FRP piping is fully pressurized to its design limit when calculating elbows' pressure stiffening effect. This approach corresponds to the older BS 7159 code, and it might yield to significant over-estimation of pressure stiffening effect on FRP/GRP elbows.

So, change that setting parameter and then re-run the application See what load change you get...

Regards,