slabs beam detailing

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Design and drawing of RC Structures

CV61

Dr. G.S.Suresh

Civil Engineering Department

The National Institute of Engineering

Mysore-570 008

Mob: 9342188467Email: 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 each

Width of beam = 200mm

Overall depth of beam = 300mm

Width in intermediate supports = 200 mm

Main reinforcement = 4 Nos -12 mm diameter bars with 2 bars bent up

Anchor/hanger bars= 2-10 mm diameter

Stirrups = 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 =3.2m

Overall depth at free end = 150 mm

Overall depth at fixed end = 450 mm

Width 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 dia

Nominal stirrups = 6mm dia at 40 mm c/c

Bearing at fixed end = 300 mm

Use 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 end

Hanger 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 = 4m

Support width = 300mm

Size 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 tor

Stirrups: 2L-8 tor @ 200 c/c

Use M20 concrete and Fe 415 steel

Draw longitudinal and cross section if the beam is

1. T-beam

2. Inverted T-beam

3. 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

Dr.G.S.Suresh19

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

Dr.G.S.Suresh20

Introduction

Dr.G.S.Suresh21

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

Dr.G.S.Suresh22

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

Dr.G.S.Suresh23

Introduction

Dr.G.S.Suresh24

Introduction

• Torsion Reinforcement shall be provided as shown in Fig.

Dr.G.S.Suresh25

Torsion Reinforcement

Dr.G.S.Suresh26

Torsion Reinforcement

Dr.G.S.Suresh27

Typical One Way slab

Dr.G.S.Suresh28

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 m

Span of the beams = 7.23m

Beams are supported on walls of 0.23 m thickness

C/s of beam = 230 x 450 mm

Grade of concrete : M20

Type of steel : Fe415

Clear cover : 20 mm

Slab thickness: 150 mm

Beam 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/c

Main reinforcement in other interior panels = 8 mm diameter @ 200 c/c

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

Distribution 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 end

Hanger bars: 1-12 mm dia

Two 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