external steel reinforcement

[bjb]

I have 2 openings that the architect wants to cut into some existing cast-in-place concrete walls that are supporting a precast plank roof. I am considering possible reinforcing by externally bonding some steel plates at the bottom of the opening. I know that epoxy bonding carbon fiber is another way to do it, but I only have 2 openings and don't want to get specialty engineers or contractors involved.

The problem is, I am unsure of the way to design this. My thought is to conservatively use an allowable stress approach to check the stress in the steel, considering the modular ratio and calculating "j" and "k". I would then "bond" the steel to the concrete using drilled-in adhesive anchors. I consider this as a conservative but quick and dirty approach as a possible alternative to sizing a steel beam to span the opening.

 

[tincan]

Construct a channel frame around the opening. Channel legs around the concrete. Size to fit snugly. If critical have holes punched at intervals in the channel and drill and use Hilti inserts. Its a Micky Mouse solution but have used it in several occasions with no problems.

Best Tincan

 

[bjb]

I have used that solution myself sometimes. I know I can do this or just size a beam to span the opening. I am looking to see if anyone has a procedure to design externally bonded reinforcement for concrete members.