The beam protruding from the wall is called explosion-proof retaining beam, which is usually designed in the protection zone, that is, on the wall opposite to the civil air defense door frame. Another point is that the bottom elevation of retaining beam is the top elevation of embedded door frame.
the doors, walls and other components of underground civil air defense works must be blast-resistant and resist the impact force of shock waves, and the same is true for civil air defense doors. Therefore, there is no non-explosion-proof facility beam on the civil air defense door.