Reinforcement around openings in slabs and walls

[BFstr]

Hi Every one,

Dose anyone know the principals of sizing extra re-bars (diagonals, and vertical, horizontals) around wall openings in reinforced concrete walls and slabs?

Is there calculation or just code requirement?

The wall that I am working on has a 14" pipe going through at the base of wall - it is a retaining wall (I don't know the rules are different for retaining walls compare to ordinary building walls?

Please direct me. If you know of any good reference I will appreciate letting me know.

Sincerely,
BFstr

 

[oneintheeye]

generally any bars displaced by hole spread them around hole, so if you lose 4 bars vertically place 2 additional each side of hole, same horizontally. This should take care of the stress increase around hole. Provide diagonals around hole possibly to. This is a general rule and local forces should be considered. I would imagine the above would suffice for a 14 inch hole, you need to consider the depth of the wall and the forces at this location though, which you haven't stated.

 

[miecz]

For a discussion on the main reinforcing, see thread507-170996.

The diagonal reinforcing is added to provide a smooth load path around the opening. I've never seen any literature that presents the theory. It's just a standard practice in the industry.

 

[jike]

Make sure that foundation dowels are provided for the added verticals. A standard detail, done properly, should cover 99% of the cases. For small openings, require the bars to be splayed (snaked) around opening.

For very unusual situations with multiple holes or high diaphragm stresses, a more in-depth analysis (FEM) may be warranted.