Cut a hole in an existing grade beam/wall
Cut a hole in an existing grade beam/wall
(OP)
I have a project where a 50" square ventilation shaft must be cut into an existing 11'-0" tall concrete sub grade wall that is also acting as grade beam between conrete piers. The opening is centered in the neutral axis of the wall/beam and in the mid span of the wall/beam. The opening is located below the compression area and above the steel in the bottom of the wall. The question now is what kind of forces are going to be around this opening? The top remaining concrete header will be sufficient for the gravity loads above the ventilation shaft, but our biggest concern is the force concentrations around the new opening.





RE: Cut a hole in an existing grade beam/wall
RE: Cut a hole in an existing grade beam/wall
The reinforcement in the wall should be symmetrical about the opening, so at this point I am assuming that the opening is located in the NA. The calculated depth of the compression block is well above the top of the opening, so we are somewhere close. If I understand you correctly, line the sides of the opening with double angle, bent plate, or flat plate and bolt to the sides of the opening to acheive what ever the shear force is at that point. Top and bottom will only be alinged to proved for attachment of the steel grate?
RE: Cut a hole in an existing grade beam/wall
RE: Cut a hole in an existing grade beam/wall