Hi Luciano,

I can't find also a fatigue curve for FRP Pipe. As a simple estimate you can use the fatigue curve for PD5500 and using the modulus of Elasticity of the FRP in the formula given in that Code you can have an S-N Curve. Also you can use a Finite Element Program (FE-Pipe, Ansys,etc...) to get the Peak Stresses at Tees, Bends using the material properties, geometries of FRP and calculate the SIF's to be applied to your Beam Element Program such as Caesar.

A correction in my interpretation is most welcome.

Hope this helps,
Cheers!!!