Hi Martymm,

just to add another view on this matter:

I have been performing dynamic analyses on pipe systems for 25+ years. When tools and technology advanced over the years it has become more easy to include more details in modelling (such as support stiffness or include complete supporting structures like pipe racks). That is the path of trying to describe reality as accurate as possible.
But there is another path (strategy) as well: use simple modelling (e.g. assume rigid supports) and see what the problems are. When the design is OK then you know that with rigid supporting you can achieve good results. Then recommend to your customer to check (and possibly improve) support stiffness.

This second approach keeps calculations not only simple but also more reliable. You show to the customers how a good (dynamic) design can be achieved and leaves it to the customer how to realize it.