Slabs Beam Reinforcement Detailing

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Design and drawing of RC Structures

Email: gss_nie@yahoo.com

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DETAILING OF BEAM &SLAB

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Learning out Come• Review of detailing of beams• Continuous rectangular beams• Cantilever rectangular beams• Flanged beams• Introduction to detailing of slab• One way slab

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PROBLEM No. 3 Draw the Longitudinal section and two cross sections one near the support and other near the mid span of a RCC continuous beam with the following data:Clear span of beams = 3m eachWidth of beam = 200mmOverall depth of beam = 300mmWidth in intermediate supports = 200 mmMain reinforcement = 4 Nos -12 mm diameter bars with 2 bars bent upAnchor/hanger bars= 2-10 mm diameterStirrups = 6 mm diameter @ 300 mm c/c.Materials : HYSD bars and M20 grade concrete

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PROBLEM No. 3

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PROBLEM No. 4 A rectangular beam of cross section 300 x 450 mm is supported on 4 columns which are equally spaced at 3m c/c. The columns are of 300 mm x 300 mm in section. The reinforcement consists of 4 bars of a6 mm diameter (+ve reinforcement) at mid span and 4 bars of 16 mm diameter at all supports (-ve reinforcement). Anchor bars consists of a 2-16 mm diameter. Stirrups are of 8 mm diameter 2 legged vertical at 200 c/c throughout. Grade of concrete is M20 and type of steel is Fe 415. Draw longitudinal section and important cross sections.

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PROBLEM No. 4

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PROBLEM No. 5 Draw to scale of 1:20 the Longitudinal section and two cross-section of a cantilever beam projecting 3.2 from a support using following data

Clear span =3.2mOverall depth at free end = 150 mmOverall depth at fixed end = 450 mmWidth of cantilever beam = 300 mm

Main steel = 4-28 mm dia with two bars curtailed at 1.5m from support

Anchor bars = 2 Nos. 16 mm diaNominal stirrups = 6mm dia at 40 mm c/cBearing at fixed end = 300 mmUse M20 concrete and Fe 415 steel

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PROBLEM No. 5

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PROBLEM No. 6A cantilever beam with 3.2m length is resting over a masonry wall and supporting a slab over it. Draw to a suitable scale Longitudinal section, two cross-sections and sectional plan with the following data:Size of beam = 300 mm x 350 mm at free end and 300 mm x 450 mm at fixed end and in the wall up to a length of 4.8m Main steel: 4 nos. of 25 mm dia bars, two bars curtailed at 1.2m from free endHanger bars: 2 nos. 16mm.Stirrups: 6mm dia 2 legged stirrups @ 200 mm c/c the support length and @100 mm c/c from fixed end up to length of 1m @ 150mm c/c up to curtailed bars and remaining @ 200 c/c.

Use M20 concrete and Fe 415 steel

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PROBLEM No. 2

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PROBLEM No. 7 A beam has following data

Clear span = 4mSupport width = 300mmSize of web = 350 x 400 Size of flange = 1200 x 120mm

Main reinforcement in two layers : 3-20 tor + 3-16 tor and to be curtailed at a distance 400 mm from inner face of support Hanger bars: 3- 20 torStirrups: 2L-8 tor @ 200 c/cUse M20 concrete and Fe 415 steel

Draw longitudinal and cross section if the beam is1. T-beam2. Inverted T-beam3. L-Beam

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PROBLEM No. 5

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Dr.G.S.Suresh18

Introduction

• 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 Slab

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Introduction

• Slabs 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

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Introduction

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Introduction• Thickness of the slab is decided based on

span to depth ratio specified in IS456-2000. Min reinforcement is 0.12% for HYSD bars and 0.15 % for mild steel bars.

• The maximum diameter of bar used in slab should not exceed 1/8 of the total thickness of slab

• Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm which ever is less

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

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Introduction• Generally 15 mm to 20 mm cover is

provided for the main reinforcements • Alternate main bars can be cranked near

support or could be bent at 1800 at the edge and then extended at the top inside the slab as shown in Fig

• Curtailment and cranking of bars and is shown in Fig

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Introduction

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Introduction

• Torsion Reinforcement shall be provided as shown in Fig.

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Torsion Reinforcement

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Torsion Reinforcement

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Typical One Way slab

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Typical Two Way slab

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PROBLEM Prepare a detailed structural drawing of one way continuous slab for a hall of clear dimensions 7m wide and 11.77 m long, use following data

Centre to centre distance of supporting beams = 3.0 mSpan of the beams = 7.23mBeams are supported on walls of 0.23 m thicknessC/s of beam = 230 x 450 mmGrade of concrete : M20Type of steel : Fe415Clear cover : 20 mmSlab thickness: 150 mmBeam depth is inclusive of slab depth, The hall is having walls on

all 4 sides

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PROBLEM Main positive reinforcement @ end span = 8mm

diameter @100 c/cMain reinforcement in other interior panels = 8 mm

diameter @ 200 c/cNegative reinforcement @ all supports = 8mm diameter

@ 200 c/cDistribution steel= 8mm diameter @ 200 c/c

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PROBLEM

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No. 1

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No. 2

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No. 3

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No. 4

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No. 5

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Do it Yourself

1. Draw the longitudinal section and typical cross sections ( at centre and support), and show the reinforcement details in a simply supported rectangular beam of size 300 mm x 500 mm, clear span 5m supported on walls of 0.3m, use a suitable scale Reinforcements: Main: 4 No. 16mm dia with 2 No. cranked at 1m from centre of support. Stirrup holders 2 Nos. of 12 mm dia Stirrups: 2 legged 8 mm dia stirrups at 250 mm c/c in the central 2m span and 2 legged 8 mm dia stirrups at 150 mm c/c in the remaining portion. Assume concrete M 20 grade and steel Fe 415, and suitable cover. Prepare the bar bending schedule and calculate quantity of steel and concrete required.

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Do it Yourself

2. Prepare the bar bending schedule and estimate quantity of steel and concrete after drawing the longitudinal and cross section. Other details are Span of beam = 4.2 m

Cross section at support end 300 x 600 mm and cross section at free end 300 x 150 mm

Reinforcements:Main tension steel: 4-20 mm dia, 2 bars are curtailed at a distance

of 2m from free endHanger bars: 1-12 mm diaTwo legged stirrups 8mm dia @ 140 mm c/c for full length.

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Dr. G.S.Suresh

Civil Engineering Department

The National Institute of Engineering

Mysore-570 008

Mob: 9342188467 Email: gss_nie@yahoo.com