I was wondering that too.
If you look at the next picture after that, it looks like the same hinge (or a similar one).  My guess is that somebody tacked the hinges in place, painted over the slag, and he came in, ground it out, and made the pretty weld in pic 4.

jrw159  the fourth picture is what I replaced the third picture with....yea those were pretty bad and there were a lot of them.

Northweldor  The last two are the same job.  Had to crawl inside those and weld rebar/plates together in the precast for what they called "earthquake proofing".  That job turned into some expensive handrail I am building right now.