Steel Arrangement Around Slab Opening

Reduction in critical design section for moment due to opening, can be overcome providing more closely on each side of the opening to maintain the necessary As. This is possible only when opening is possible to locate where moment is well below the compression capacity of the slab, thereby leaving the arrangement of reinforcement as the only problem. Of course, shear strength must be maintained, but this is rarely a problem except near the columns in flat slab type, as noted previously.

The arrangement of bars around any but minor opening can constitute a real problem. Bars running perpendicular to the face of an opening are not fully effective when simply cut0off at the opening. 
 
This is acceptable if there is a beam at the opening to act as reaction for the slab. If there is no beam it is better to fan the bars out or splay them to go around the opening. If fanning or splaying leaves too wide an area without steel, extra bars can be placed parallel to the side of the opening, as indicated.


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.

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