You need to model the rebars with line bodies, not 3D solid parts (hence why it is almost impossible to mesh these rebars). Perhaps spaceclaim can convert some of them automatically to line bodies (beams).
See the To extract a beam from a solid tool in Spaceclaim.
(tutorial for this tool:https://www.youtube.com/watch?v=cRAmDQMaBAA)
Also see this presentation which presents the recommended workflow of modelling RC structures.
(With this workflow one does not need to connect the line bodies representing the rebars since they will be embedded in the concrete using the reinforcement option shown on slide 6, so any overlap is fine)