Here is another angle:
The whole video:
On of the 2 comments mentions Komatsu and that means bulldozers & excavators.
My guess is the bottom part of the rotating upper body of an excavator.
Something similar turned up in the same iamge search:
PHMX 4436 | Except for a spacer all of the cars were multi-t… | Flickr contains photo, according to the guy who posted the photo, of a crane turntable
The photo posted by Frenchy can be found here together with some other turntables and excavator parts:
Parts (hub?) for a windmill
