Recommendations for detailing reinforcement in reinforced concrete works
1969 Edition

IS 5525 advises several accepted methods for splicing reinforcement bars, including lap splicing where bars overlap and are tied together, preferably located at points of minimum stress such as inflection points. It is recommended to avoid lap splices for large diameter deformed bars (45 mm and 50 mm) in tension zones. Butt splicing through arc or fusion welding and mechanical couplers is suitable especially for bars 32 mm and above, commonly used in vertical columns to reduce congestion. Splices must be staggered to prevent weakness concentration, and the designer should specify splice type and location in accordance with IS 456 and IS 2751.

To maintain the position of bundled bars during concreting, they must be tightly tied, wired, or fastened. For compression splice zones where bars bear end-to-end, additional ties should be placed on either side of the splice to maintain concentricity. In tension splices involving short bars, the bundle size should be limited to four bars and these must be tied within the bundle. Corner ties are essential at each bundle to prevent spreading. For offset bent vertical bars in columns, three close ties within eight bar diameters of the bend are necessary. These practices ensure proper positioning and adequate concrete cover.

Spiral reinforcement in columns must extend from the floor or footing level up to the lowest horizontal reinforcement in the slab, drop panel, or beam above, or to the plane where the capital’s width is double the column’s width if capitals are present. Stub spirals or circular ties are required if lateral confinement is needed above the main spiral, facilitating reinforcement placement in floor systems. Spirals require 1.5 additional turns at both ends for proper anchorage and splicing, which can be achieved through shop welding or a lap of 1.5 turns. Stub spirals should be attached to main spirals or clearly identified for handling during transport.

Welded wire fabric (WWF) placement in slabs is indicated on the drawings by diagonal lines—bottom sheets use diagonals from bottom-left to top-right, and top sheets from top-left to bottom-right. Small sketches showing fabric orientation and mesh type (square or oblong) accompany the plans. Schedules must detail mesh size, length, width, and cutting instructions for each slab panel, following formats illustrated in the standard. Laps should be avoided in maximum stress areas; if unavoidable, laps must be spaced at least the wire spacing plus 50 mm apart. This approach ensures clear guidance for positioning WWF in slabs.

To reduce congestion at beam-column junctions, IS 5525 recommends placing beam reinforcement bars at elevations different from those of girder bars to avoid clashes. Large-scale detailed drawings should be provided at these intersections to clearly guide steel placement. Lateral ties and spirals in columns should be arranged to minimize the density of intersecting ties within the core, following IS 456 guidelines. For column bar offsets less than or equal to 75 mm, offset bends are used; for greater offsets, bars are terminated, and dowels employed to maintain continuity. These measures facilitate reinforcement placement and maintain concrete flow.