hi,

as I am doing a GRE system according to Iso 14692, it occurred to if I had to assume 'joints' at the pipe joints connection points? I am not going to model wall thickness of those connections 'thicker' than the rest of the piping.
please reflect.

many thanks in advance,

I'll preface this with me not being an ISO 14692 user. However, physically speaking:

The stiffer the joints with respect to the pipe, the more load will concentrate into the joints.

The more length of the piping system devoted to joints, even more load will concentrate into those joints.

If your piping system consisted of nothing but joints and practically no pipe, it'd be a clear cut case where you should use the thicker geometry, correct?

Without joints, there's no need to consider the added thickness at all.

Anywhere between will be just that - somewhere between.

Allowables for FRP/GRE can be quite low. I have a tendency to treat them with a higher abundance of caution and have included that extra geometry.