I am working on a piping system partially supported by "pendulum" supports (on the ground, each support is almost 5m long) and partially sitting on the steel structures (independent structures like piperack, valve platforms and etc). I understand that the acceleration created at the height of the piping sitting on the structures should be different than the ground acceleration and I probably have to make various time-acceleration spectrums. I just do not know how to add up the pendulum behaviours in the calculation. I wonder if anyone has a second thought on this matter. I have attached the drawing of a pendulum support for those who might not know what a pendulum support is.