That depends on the pipe size and what they're filled with. If they're 3" pipes filled with water, for example, figure that all the pipes will be filled with water, find the weight per linear foot (or look it up). Design your beams with two worst case scenarios- the a pipe being hung parallel...
The eccentricity between the applied force and the resisting weld (the weld to the structure below) will cause a moment, putting one end of the assembly in tension and one other side in compression. I'd start by checking for buckling in the web. You'd then need to check the weld strength for...
Bolt a ledger to masonry, embed some straps around masonry rebar. Nail straps to top of joist for out of plane connection, use a simpson hanger for TJI.
Is there some facet of the masonry firewall that I'm not catching onto that will prohibit this solution?
