Had a silo like that here, built in 1972.

Was always an interesting day lifting the unloader and closing the doors.  Occasionally would get a third or halfway to the top and a bottom door would pop open beneath you, would need to open them all back up again and start over from the bottom. Fun times.  

Learned a lot of life lessons, curse words, and how to handle stress dealing with that silo and its wore out Patz 98B unloader.

Was not a bad day when the concrete in that structure became fill under my heifer barn.