Steel Requirement to Avoid Opening Effect in Slab

With regard to flexural requirements, the total amount of steel required by calculation must be provided, regardless of opening. Any steel interrupted by holes should be matched with an equivalent amount of supplementary reinforcement on either sides, proper lapped to transfer stress by bond.

If minor cracking at the corners of an opening is objectionable, it is always advisable to add one or two diagonal bars at each corner, especially at large openings. Bars are always desirable around Window and door opening in concrete wall slabs, because such reinforcement helps to take care of shrinkage stresses.

Code Requirement

13.5.2.1 In case of opening in intersecting middle strips, total amount of reinforcement required for the panel without opening is maintained.

13.5.2.2 In case of opening in intersecting column strips, an amount of reinforcement equivalent to that interrupted  by  an opening shall be added on the sides of the opening.

13.5.2.3 In case of opening common to one column strip and one middle strip not more than ¼ the reinforcement in either strip shall be interrupted by openings. An amount of reinforcement equivalent to that interrupted by an opening shall be added on the sides of the opening.