Reinforcement Detailing

Reinforcement DetailingInstitute of Technology, Nirma UniversityDepartment of Civil EngineeringM-Tech CASAD

Prepared By: guided by:Yash Khandol P.V. Patel

IntroductionDetailing isoftenconsideredtobethepreparationofworking drawings showingthesizeandlocationofthereinforcementina concrete structure.

Detailing involves the communication of the engineers design to the contractors who build the structure. It involves the translation of a good structural design from the computer or calculation pad into the final structure.

Good detailing ensures that reinforcement and concrete interact efficiently to provide satisfactory behavior throughout the complete range of loading.

Engineering drawing prepared by the designer should specify grades of concrete and steel, live load, dimensions, reinforcement, building the forms, fabricating the reinforcement and placing the concrete.

Notes and statements should be clear and unambiguous.

Guidingprinciples:DeterminelocationanddirectionofallinternalforcesUseadequatelyanchored reinforcementwhereveratensile forceisrequiredforequilibrium; Useductilereinforcementwhenthe reinforcementisrequiredforstrength; Neverrely ontheconcretesabilitytocarrytension(itmaynot exist); Includeadequatequantitiesofreinforcementforcrackcontrol;Ensuresteeldetailsarepractical andthatsteelcanbefixedand concrete canbe satisfactorilyplacedandcompactedaround complexdetailswith adequatecover;Ensuredetailsareeconomical.Aims Main aims of RCC detailing are:

Providing an outline of the concrete to give necessary information regarding formwork to provide finished section of the desired size.

Providing enough reinforcement details for fabrication of the steel skeleton and its placement in the desired position.

DETAILING OF BEAMSIntroduction

Carries Transverse External Loads That Cause Bending Moment, Shear Forces And In Some Cases Torsion.

Concrete is strong in compression and very weak in tension.

Steel reinforcement is used to take up tensile stresses in reinforced concrete beams.

Mild steel bars or Deformed or High yield strength deformed bars (HYSD)

HYSD bars have ribs on the surface and this increases the bond strength at least by 40%

Deformed bar and plain bar

Anchorage in steel bars is normally provided in the form of bends and hooks.

The anchorage value of bend of bar is taken as 4 times the diameter of bar for every 45* bend subjected to maximum of 16 times the diameter of bar.

Nominal cover, should not be less than the diameter of bar.

For durability requirements, minimum nominal cover shall not be less than the values given in IS :456-2000, p.47, table-16.

Exposure Nominal concrete cover in mm not less thanMild 20Moderate 30Severe 45Very severe50Extreme 75Generally a beam consists of following steel reinforcements: (IS : 456-2000, P.46, cl. 26.5.1)

Longitudinal reinforcement at tension and compression face.

Minimum tension reinforcement in beam : Mild steel= 0.34% of effective area of beam HYSD bars=0.20% of effective area of beamMaximum area of tension and compression reinforcement ,shall not be more than 0.04 bD (4%)

Shear reinforcements in the form of vertical stirrups and or bent up longitudinal bars are provided. Maximum spacing of shear reinforcement: 1) 0.75d for vertical stirrups or D for inclined stirrups at 45* 2) 300 mm Not greater than smaller of two values. Side face reinforcement in the web of the beam is provided when the depth of the web in a beam exceeds 750 mm.Specification for the reinforcement in beams is given in clause 8.1 to 8.6 of SP34

Main reinforcement = 5 Nos -12 mm diameter bars with 2 bars bent up at L/7 from centre of support

Anchor/hanger bars= 2-10 mm diameter

Stirrups = 6 mm diameter @ 200 mm c/c.DETAILING OF SLABIntroduction Used for covering spaces in the form of roof or floor .Slab may be supported on walls or beams or columns . Slab supported directly by columns are called flat slab .One Way Slab Two Way SlabSlabs could be simply supported, continuous or cantilever In two way slab the corners may be held down by restraints or may be allowed to lift up Additional torsion reinforcement is required at corners when it is restrained against uplifting as shown in Fig

Min reinforcement is 0.12% for HYSD bars and 0.15 % for mild steel bars. ( IS 456-2000, P.48, cl. 26.5.2)

The maximum diameter of bar used in slab should not exceed 1/8 of the total thickness of slab . ( IS 456-2000, P.48, cl. 26.5.2.2)

Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm which ever is less .( IS 456-2000, P.46)

For distribution bars the maximum spacing is specified as 5 times the effective depth or 450 mm which ever is less .

Min diameterFor main steel:( SP34) For plain bar 10mm For deformed bar 8mmFor distribution steel: Min dia=6mm

Typical One Way slab

Typical Two Way slab

DETAILING OF COLUMNSIntroduction :( IS 456-2000, P.48, cl. 26.5.3)

For a longitudinal reinforcing bar in a column nominal cover shall in any case not be less than 40mm, or less than the dia of such bar.

The cross-sectional area of longitudinal reinforcement shall not less than 0.8% nor more than 6% of the gross c/s area of the column.

The bars shall not be less than 12mm in dia.

The minimum number of longitudinal bars provided in a column shall be four in rectangular and six in circular columns.

Spacing of longitudinal bars measured along the periphery of the column shall not exceed 300 mm.

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