Rhytmic planes under a surface (bridge structure)

Hi,
I want to model the beams of a bridge like in this photograph of the campo volantin bridge from santiago calatrava.
image

I already tried it with by making a loft with a few curves under the surface and then dividing the loft with brep plane.

but this is not very effective since i want to use the borders of the surface.

With which nodes i might accomplish this>?