Hello,
I am designing the shear reinforcement in a straight pier cap for a multi-column pier. The issue I am having is that whenever I increase the number of legs for my stirrups, the area of steel required also increases to the point where increasing the number of legs is just not advantageous. I'm designing the cap for shear and torsion along with magnified moments. I have attached a picture of the output for the shear and torsion design. On the left is the result from using stirrups with 2 legs and on the right is results from using 4 legs. The same bar size and spacing was used.
Is there any particular reason this is happening? I've made multiple stand-alone substructure files thinking that a new file would solve the issue, but they've all had this issue. Any help will be greatly appreciated.