Thank you everyone for your feedbacks. I actually figure it out. based my discussion with the site, I was told that there are no gaps above the pipe, which contradict with the drawings. I performed dynamic analysis and found that some rod hangers are experiencing uplift forces due to seismic. since rods don't take compessive loads, we decided to remove one support, and modify three rods to guides, since there is space to make guides at these locations.
Thank you again