In my opinion, piperack cannot be collapsed as long as a differential settlement is less than few inchs and a civil/structure engineer designs it with common sense.
First of all, tell me which part will have more settlement and what's pipe size, how big differential settlement do you expect ? Is it going to be 10 inch settlement with 100 in cooling water line ????...no, probably less than one inch with 24" pipe size because it runs on piperack.
I will assume 24" cooling water line which runs horizontally as buried pipe and has one inch differential settlement, and there is no frost heave effect at winter season.
If piperack has more settlement, the pipe weight load at first support of rack will be transferred to next support of piperack. If buried cooling water pipe settle more, the first support of piperack will have a little bit higher weight load rather than undertake the entire length of buried pipe weight. That is, the buried cooling water pipe will not be settled around off-piperack area and the pipe weight of this area will be distributed to soil and the first support of piperack..it would be less than two tons.
_________________________
Sun Wee