if you are fresh engineer in the field, I would like to suggest you to use the midas Civil software for the Post Tensioned bridge. they have good automatic design for the Post tensioined bridge as well as design report generatioin.
yes.you should be used both shears for design.
by the way, I don't understand why you used two type of elemenets. in my case, i just used the plate model in flange and web.
Now I'm useing SAP2000 and MIDAS CIVIL. those software are easier to find right result for 3D plate model design.
cheers.