I did some work like you describe. I used a masonry bit until I hit the steel "beam", then I switched to a steel bit. The steel bit was the same size at the masonry bit. As soon the steel bit was through the steel, I switched back to the masonry bit. I then inserted plastic expansion plugs and suitable screws.
Trust me this is a lot of work, especially if you do not have 2 drills. Also you will go through a lot of bits if you are not very careful. The steel bits do not like concrete, and the concrete bits do not like steel.
The builders use a SELF TAPPING screw that apparently will go through the concrete and the steel in one step, this is how they install the birdcage aluminum channels. I did not try these, but if you can find the right size, you could try this approach.
Hope this helps.
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Pennsylvania, for 60+ years, most recently, Allentown, now TV. 
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