You are modeling a structure, but not all elements or member is under structural category. The way I always remember about the definition of structural and non-structural member is:

Structural Member: Member that contributes to the stiffness of the system usually consists of primary member (piles, legs, frames) and secondary member (braces).

Non-Structural Member: Member that do not contribute to the stiffness of the system and usually only attract loading (conductors, risers, boat landings, fenders, conductor’s braces)

However, I do come cross engineers that modeled conductors as structural members, giving some sort of stiffness to the system. This can be justified by saying the conductor has its own piles, and some the axial loading will transfer directly to foundation instead of giving it all to the main structure. You can also do this but I only do it if I have structure that is really-really weak in resistance (to avoid being too conservative).

In modeling of non-structural member, most of the time I used CELLHINX command to the identified element or member.  The command looks like:

The command lines consist of Fx, Fy and Fz and we locked all three boundary conditions to make sure that the element will not take any loading and provide any stiffness to the main structure. You can see that when you apply this, the element will be always in blue color which mean it not takes any loading, hence do not fail. Even if this non-structural member does fail, it will only affect operational and not global safety of the structures.

Bear in mind that you cannot have non-structural member in in-place analysis or any other code checking analysis unless you are really sure that the element is not important at all. For global collapse, we can simplify thing. Engineering justification and sound experience is the key when setting this non-structural and structural element, because the failure mechanisms sometimes varies when you put different elements as non-structural and structural members. Well, I can’t tell you more when experience and experiment it yourself is the best way to learn in modeling!!