I've received a drawing with this detail and I don't really know why they've used it so any clues would be appreciated. Just the double layered bundles of bars at the top and bottom of the right hand section.
This is a bit of a vague question so I'm just looking for thoughts.
@ReinisGailitis: " I suspect it is more on a conservative side so that you wouldn't underestimate tension in the tie". Like your point. by the way, i tried to mean reinforcement with r/f. Thank you very much.
What do you mean by r/f?
I'm not 100% sure about the upper limit on the strut angle (>=65 degree you mentioned), but I suspect it is more on a conservative side so that you wouldn't underestimate tension in the tie.
@ReinisGailitis: Thank you very much for your point. With that approach, the strut angle can be limited. But it leads to enormous amount of r/f in the tie as the column load is fairly high. By the way, actually what is the risk of exceeding the strut angle?, is the strut will crush/ fail in shear?
Read some literature on load path method in strut-and-tie design. Also, check information on correct strut-and-tie models for pile caps - you shouldn't assume that the horizontal strut is lying on the interface of the column/pile cap - it should be positioned inside the pile cap.