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.
