There is a lot of construction going on at FRA terminal 1 right now.

Departure drop-off area is slightly constrained by construction in front of B check-in.

I presume that the same work is affecting the B check-in area.

There is no link between check-in areas and gates so AC is almost certainly going to continue to use B gates like normal.

B security is open on both sides. The work in that area seems to be completed or paused awaiting it's next phase.