Reinforcement Detailing Guide
Reinforcement Detailing plays an important role in construction as perfect detailing of engineering design in planning and engineering process can resist the collapsing of the building resulting from defective connection or detailing. Detailing also maintains the safety of the structure.
Reinforcement Detailing is important for the steel structures as well as RCC members since it translates all the mathematical expressions and equations results.
Detailing can be done the for following RCC members :-
- Slabs with or without openings (rectangular, circular, non-rectangular pyramid slab, triangular slab etc.)
- Beams with or without openings (shallow and deep beams)
- Columns with different shapes like rectangular, L, T, circular, octagonal, cross etc.
Detailing of foundations
- Detailing for gravity loads differ from the lateral loads particularly for the seismic forces.
- There is also other type of detailing necessary for the rehabilitation and strengthening of damaged structures.
Do's for detailing
- Create perfect drawings and if possible label each bar and demonstrate its shape for transparency.
- Cross section of retaining wall that collapses instantly as soon as the soil backfill is provided since 1/4 inches dia is used in spite of 1-1/4 inches dia. Problems arise since perfect rebar is covered by a dimension line.
- Create a bar bending schedule when required.
- Specify perfect clear cover, nominal cover or effective cover to reinforcement.
- Determine detailed location of opening or hole and provide sufficient details for reinforcements around the openings.
- Utilize the size of bars and spirals. The numbers various sizes of bars should be retained minimum for a single structural member.
- The grade of steel should be evidently mentioned in the drawing.
- Deformed bars should not contain hooks at their ends.
- Demonstrate enlarged details at corners, junctions of walls, beams and column joint and at same situations.
- Congestion of bars should not be provided at points where members overlap and ensure that all reinforcement are arranged perfectly.
- For bundled bars, lapped splice of bundled bars should be created by splicing one bar at a time; such separate splices inside the bundle should be staggered.
- Ensure that hooked and bent up bars are arranged and contain sufficient concrete protection.
- Specify all extension, construction and contraction joints on plan and provide details for such joints.
- The position of construction joints should remain at the point of minimum shear approximately at mid or adjacent to the mid points. It should be developed vertically and not in a sloped manner.
Do's for Beam and Slab Reinforcement Detailing
- When splices are arranged in bars, they should remain out of the sections of maximum stresses as far as possible and should be staggered.
- When the depth of beams surpass 750 mm in case of beams devoid of torsion and 450 mm with torsion provide face reinforcement according to IS456-2000.
- Deflection in slabs/beams is minimized with the compression reinforcement.
- Only closed stirrups are recommended for transverse reinforcement. For members susceptible to torsion and for members susceptible to reversal of stresses similar to seismic forces.
- To adapt bottom bars, secondary beams should be created shallower than primary beams, at least by 50 mm.
Do's for column reinforcement detailing
- A reinforced column should contain minimum six bars of longitudinal reinforcement to be used in transverse helical reinforcement for circular sections.
- At least four bars one at each corners of the should be provided in case of rectangular sections.
- Retain exterior dimensions of column fixed so far as possible to use the forms again.
- 2 grades of vertical bars should not be used in similar component.
Do Not's General
- Reinforcement should not expand over an expansion joint and the break among the sections should be finished.
- Flexural reinforcement should not preferably be discontinued in a tension zone.
- Bars greater than 36 mm dia should not be bundled.
- Lap splices should not be utilized for bars greater than 36 mm dia. Except where welded.
- When dowels are used, their diameter should not go beyond the diameter of the column bars in excess of 3 mm.
- When bent up bars are used, their participation towards shear resistance should not surpass 50% of the total shear to be countered. Single bent up bars alias cranked should not used in case of earthquake resistance structures.