The same design code that applies to all of your other piping systems will apply to fiberglass piping systems.

But the major problem design engineers have with fiberglass piping systems is assembling a competent set of design properties. Fiberglass pipe for a given size, design pressure, and design temperature can have a very wide range of bending stiffnesses.

A proper stress analysis of a fiberglass piping system requires you to obtain a great deal of this (proprietary) information from the vendor. It is not possible to do a competent analysis of a fiberglass system until you know any of these. And since the properties can be controlled by the particulars of the winding of the glass fiber, they can be changed to accommodate the requirements of the project.

Therefore, determining the most suitable properties for the fiberglass pipe is an iterative process. If you, as an independent (not an employee of the pipe manufacturer) design engineer attempt to do the detailed analysis on your own, there will be several iterations before you have a final set of material properties that work for your layout. This can be quite slow, and the pipe vendor can use your analysis time as the basis for an additional charge for external contract delays.

The fastest and most cost effective way, by far, to deal with this situation is to give the vendor coordinates, thermal movements, and allowable loads for all terminal points, and design conditions for the piping, and require him to submit the report and get it approved before he ships the pipe. That way, the iterations on design requirements vs. manufacturing requirements can happen within the same organization, and one driven by the desire to get the report filed and approved so they can ship the pipe and get paid.