Hello fellow rhino users,
Im working on a school assignment to make a parametric design of a pedestrian foot bridge. The model generated in grasshopper is a parametric design that is exported to sofistik for more detailed FEM analysis. The model is basically a girder made out of FRP with a concrete deckslab. In grasshopper the two different materials are combined by springs, the same will be done in sofistik. However, sofistik divides the upper plate of my box up in different surface areas. 
(please excuse me for my crooked drawing). In order to connect the box (showed in green) to the upper concrete plate, the upper concrete plate must have the same dimensions as the lower plate so as that the meshes are topologically identical. I did one by hand to see if it works.
this shows the principal. so i made surfaces inbetween the diagrid and moved it up. The concrete deck and the top plate are now identical in size and shape and can therefore be meshed identically and combined in sofistik. but as i said, i did this by hand and i am trying to make a parametric model, so the question is, how can i make grasshopper make surfaces automatically inbetween the diagrids?
i hope my question is clear 
Grasshopper model complete.gh (151.0 KB)
amazing forum this is