I'm reviewing a report in which the analyst claims that, for a hydrotest loadcase (HYD) on buried pipe, CAESAR II leaves the weight of water on the element rather than setting to zero like in a normal buried analysis. Depending on the length of the element this can then give large bending stresses.

Is this correct? I seem to remember a topic on this a few years ago but I can't find it

I've created a simple model but have not been able to replicate the situation..

Can Richard or Dave confirm whether for buried pipe hydrotest we should use WW+HP or W+HP?

In the current version of CAESAR II (2016 - Version 8), if all densities are zero (pipe, fluid, insulation, etc.), then water weight (WW) will be zero. When CAESAR II "buries" your pipe, these densities are all set to zero. If you bury you pipe on your own, check these densities.
You may also see some response to WW (from the above ground (non-zeroed) pipe) at the transition if your buried line continues above ground.

Dave,

Thanks for your reply.

The model has been buried using the CII soil modeller, all fluid and pipe densities at buried elements show as zero in the input echo.

I get the same answers for a simple buried model with the following two loadcases,

WW+HP (HYD)
W+P1 (OCC), where I have entered P1 and HP as the same pressure and a fluid density of 1000kg/m^3 is entered.

Did previous versions of CII behave differently for buried pipe and the HYD case?

I specifically addressed CAESAR II 2016 since that's the version I used to run my test.
I do not believe that the program has changed the application of water weight (load component "WW") in buried systems so I would assume that previous versions of CAESAR II would use the same logic.