Stirrups in a U girder

[ElpisMaximus]

I cannot imagine how a stirrup in an open U girder would look like. Would it also be just an open bar? How would a stirrup with 3 or 4 legs be placed into an open U girder section? I would really appreciate if anyone had any diagrams or reference to a textbook.

 

[JohnRwals]

Some engineers use modified stirrups for precast girder design.
I am not sure this is proper design.
This could be better for production efficiency.
-JRW