This is one I originally did for UDK but have moved it over to UE4 and it looks much better with the new materials although it still needs some work:
Currently I have it set up as one mesh with 2 materials. I’m using a mask for the concrete base to prevent that from being classed as metallic.
I’d be interested to know how others might have set it up, in particular the lightmap obviously needs to be huge as it’s a very large mesh. Would you split the mesh into multiple parts and have multiple materials?