Anyone able to shed any light on this issue?

We are doing analysis to EN13480 design code, for conservatism we have opted to not invoke the EN13480 option for in-plane/out-plane sifs option and hence weldolet sifs etc are calculated to be same as unreinforced tees.

We are now in a position where we have decided to invoke this option on a model to help resolve high stress at a modified location having a weldolet installed.

The high stress point is now at a location on a straight bit of pipe well away from the location and it is overstressed now and wasn't before activating the in-plane/out-plane clause.

I have looked at the raw data and forces and moments are identical, done the calcs and agree with the stresses obtained before invoking the option but not once invoked the option.

I have therefore created the simplest model possible, a cantilevered beam 1m long at 100degC, 26bar, 1.03345 matl, 1"NB 2.6mm wall and done a simple 3 loadcase run OPE, SUS, EXP.

The attached PDF shows the model, the config setting box option and the forces, moments, stresses and code stress for both runs, I have calculated the stresses and get the CAESAR II results exactly for the first run only.

Only thing I can see is that by invoking the option the internal mechanism of CAESAR II seems to then multiply stresses, I thought it was a sif issue but not sure as the individual stresses are calculated differently also. It may be that there is a logical explanation but for a straight bit of pipe I'd have thought the stresses would be the same when the base forces and moments are the same and the sif is 1.

I have even looked into whether the option uses reduced wall thickness accounting for corrosion etc but those stresses don't correlate either.

Regards.

I coded the model from your PDF, but I cannot reproduce your issue. Both of my runs yield the same stresses (regardless of that Configuration switch).

Please send me your job file as well as your configuration file (in case anything else differs from the default). Also, please advise what version of CAESAR II you're running.

Richard.

How do I send it to you?

We are using Cii Ver 8.00.00.5604 (Build 160315)

Cheers.

Andy.

Andy,

We can reproduce it here now. Rich will respond soon...

Rich/Dave.

Its nearly 19:30 here so off home soon.

Will review forum in the morning and see what's the solution (I'll bet I am doing something wrong!).

Cheers for looking into it for me.

Kind regards.

Andy.

For anyone interested, the cause of the increased stresses following the activation of the EN13480 in-plane/out-plane sif on the straight pieces of pipe is now resolved and understood (Richard - many thanks for your time looking in to the issue and explanations).

In essence (and something I omitted to put in my original post when I described the simple model) the difference is caused by the corrosion allowance within the model.

When the analysis is run without activating the check box, the software undertakes the analysis and doesn't consider the corrosion allowance.

When the check box is activated to calculate a reduced sif (especially for weldolets which are considered as un-reinforced T's when not activated) the software then considers the corroded section and hence increased stresses.

From the correspondence with Intergraph I'm not sure whether this is something that is to be changed or some note added to the config box explaining the change doesn't just affect the sif calculation it also changes the workings to consider corrosion.

I have included the pdf showing the calculation when considering the reduced section and it can be seen the results match the run when the check box is activated (In hindsight wish I'd considered corrosion on its own when I did the calc originally)

Regards.

Andy.

Good idea an explanatory note regarding the use of mill tolerance and/or corrosion.

Regards,