Video showing one type of bottom hinge pivot used on commercial aluminium doors.
This one was loose and allowed the door to drop. The top arm then disconnected from the square drive of the door closer, luckily the door wedged against the frame and did not fall on top of anybody.
See below for more on this.

Showing the new top arm in situ, these have to be adjusted carefully and clamped firmly into position. We always use threadlock to stop it coming loose or going out of alignment.
The original arm was damaged as the closer disconnected.

The door is now back on and working fully. With the bottom pivot adjusted correctly the top arm can clamp the closer firmly and so cope with the daily abuse this communal door takes.