The stronghold on my world generated completely weird, without a floor and without connecting to other parts of the stronghold.
I wont send any pictures cause I'll let you check it out.

World seed: -6875814881851113998
Then the stronghold is at: -260 39 -600

PS: This world was randomly generated without a seed in the latest 1.9 snapshot 15w31c

Hope I help in some way