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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
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 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: [email protected]
