Design and drawing of RC Structures CV 61

Design and drawing of RC Structures CV 61 Dr. G. S. Suresh Civil Engineering Department The National Institute of Engineering Mysore-570 008 Mob: 9342188467 Email: gss_nie@yahoo. com 1

DETAILING OF BEAM &SLAB 2

Learning out Come • • • Review of detailing of beams Continuous rectangular beams Cantilever rectangular beams Flanged beams Introduction to detailing of slab One way slab 3

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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 = 3 m each Width of beam = 200 mm Overall depth of beam = 300 mm 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 M 20 grade concrete 5

PROBLEM No. 3 6

PROBLEM No. 4 A rectangular beam of cross section 300 x 450 mm is supported on 4 columns which are equally spaced at 3 m c/c. The columns are of 300 mm x 300 mm in section. The reinforcement consists of 4 bars of a 6 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 M 20 and type of steel is Fe 415. Draw longitudinal section and important cross sections. 7

PROBLEM No. 4 8

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PROBLEM No. 5 Draw to scale of 1: 20 the Longitudinal section and two crosssection of a cantilever beam projecting 3. 2 from a support using following data Clear span =3. 2 m 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. 5 m from support Anchor bars = 2 Nos. 16 mm dia Nominal stirrups = 6 mm dia at 40 mm c/c Bearing at fixed end = 300 mm Use M 20 concrete and Fe 415 steel 10

PROBLEM No. 5 11

PROBLEM No. 6 A cantilever beam with 3. 2 m 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. 8 m Main steel: 4 nos. of 25 mm dia bars, two bars curtailed at 1. 2 m from free end Hanger bars: 2 nos. 16 mm. Stirrups: 6 mm dia 2 legged stirrups @ 200 mm c/c the support length and @100 mm c/c from fixed end up to length of 1 m @ 150 mm c/c up to curtailed bars and remaining @ 200 c/c. Use M 20 concrete and Fe 415 steel 12

PROBLEM No. 2 13

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PROBLEM No. 7 A beam has following data Clear span = 4 m Support width = 300 mm Size of web = 350 x 400 Size of flange = 1200 x 120 mm 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: 2 L-8 tor @ 200 c/c Use M 20 concrete and Fe 415 steel Draw longitudinal and cross section if the beam is 1. T-beam 2. Inverted T-beam 3. L-Beam 15

PROBLEM No. 5 16

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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 18 Dr. G. S. Suresh

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 19 Dr. G. S. Suresh

Introduction 20 Dr. G. S. Suresh

• • Introduction Thickness of the slab is decided based on span to depth ratio specified in IS 456 -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 21 Dr. G. S. Suresh

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 22 Dr. G. S. Suresh

Introduction 23 Dr. G. S. Suresh

Introduction • Torsion Reinforcement shall be provided as shown in Fig. 24 Dr. G. S. Suresh

Torsion Reinforcement 25 Dr. G. S. Suresh

Torsion Reinforcement 26 Dr. G. S. Suresh

Typical One Way slab 27 Dr. G. S. Suresh

Typical Two Way slab 28 Dr. G. S. Suresh

PROBLEM Prepare a detailed structural drawing of one way continuous slab for a hall of clear dimensions 7 m wide and 11. 77 m long, use following data Centre to centre distance of supporting beams = 3. 0 m Span of the beams = 7. 23 m Beams are supported on walls of 0. 23 m thickness C/s of beam = 230 x 450 mm Grade of concrete : M 20 Type of steel : Fe 415 Clear cover : 20 mm Slab thickness: 150 mm Beam depth is inclusive of slab depth, The hall is having walls on all 4 sides 29

PROBLEM Main positive reinforcement @ end span = 8 mm diameter @100 c/c Main reinforcement in other interior panels = 8 mm diameter @ 200 c/c Negative reinforcement @ all supports = 8 mm diameter @ 200 c/c Distribution steel= 8 mm diameter @ 200 c/c 30

PROBLEM 31

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No. 1 33

No. 2 34

No. 3 35

No. 4 36

No. 5 37

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 5 m supported on walls of 0. 3 m, use a suitable scale Reinforcements: Main: 4 No. 16 mm dia with 2 No. cranked at 1 m 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 2 m 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. 38

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 2 m from free end Hanger bars: 1 -12 mm dia Two legged stirrups 8 mm dia @ 140 mm c/c for full length. 39

Dr. G. S. Suresh Civil Engineering Department The National Institute of Engineering Mysore-570 008 Mob: 9342188467 Email: gss_nie@yahoo. com 40