As an inclusion in the structure. If you include walls, beams, columns, slabs, long term settlement in your modeling (even if as a continuum, which always has some shortcomings since not corresponding to the actual behavior in many cases) you will see the included beam deform and get elements for design.
Tie-Beams like these were a big betterment of wood inclusions, since fitting to the rest of the building was much better, and so the likelihood of the overall structure losing the wanted geometry that ensures some known (or purportedly known) load path was diminished. In that role, included beams didn't need much reinforcement, say from 2 to 4 #3 or #4, you can see it in the masonry codes of the seventies' even.
Then, going upwards in height, we started to get cases of masonry walls unloading (sometimes through concrete creep, or just inability to sustain the loads) in the lower beams included in the floors. A pathology appeared with diagonal cracks from the bottom corners of masonry panels ... secondary equilibrium was attained with the included beams working as ties, but too late, you had the cracks already in façades. So corrective measures were introduced, first cut the number of stories that may unload on some façade beam. Usually this is done every 3 stories a horizontal joint (of course not forgetting to include as much fittings as needed to ensure stability of whatever built, say, under earthquake or wind). Second, calculate your included beam for the potential effects -imbued deformation- such unloading scheme may produce. One can go over conservative here but normally if the number of stories that may unload (load) the included beam is small, not much reinforcement results even if you count all the stories between joints loading in the lower beam. In the process, ensure that the limits of deflection for RC members as per the code are respected, long term included.
