The wireframe isn't very neat, so i deleted some of it, to create a cleaner rythm.
_extract wireframe from this new, offset surface.
_offset surface, in order to extrude the beams so that they will follow the original curvature.
_extract wireframe. The middle curve isn't closed, so i extracted a section from the solid, and replaced it. I lofted the series of curves, and obtained a surface more of less the same.