Boolean Cut on Model

Hello all, I am trying to cut 7 segments on a model beam usinNew Hydrovent 8-29-16.blend (581 KB)g 2.73. I am not sure what I am missing but when I try to perform the boolean the beam disappears and the edges remain on the segment I am trying to cut. See screen shots below, I also attached my main model.



Why have you asked this again when you already had an answer to this a couple of days ago in your previous thread asking exactly the same thing.!