I believe up until this point you were ignoring the cold line in your model. To get this axial reaction, I think you'll have to build a little more.

Model your supporting steel as a pipe. Support this pipe with your swing models. Add nodes on this pipe where the hot & cold lines rest. If you U-bolts are tight, define X, Y, & Z restraints at these new nodes defining CNodes using the hot & cold line contact points. You might have to add a rotational restraint on one side to keep things stable.

It may sound like a lot of work but if you choose proper node numbers, the duplicate feature will make it easy. Build a couple spans and test them before running the entire system.