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Design and drawing of RC Structures CV61

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Design the slab, portal frame and foundations and sketch the details of reinforcements. ... The reinforcement is computed using table 2 of SP16. 24. Step4: ... – PowerPoint PPT presentation

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Title: Design and drawing of RC Structures CV61


1
Design and drawing of RC StructuresCV61
Dr. G.S.Suresh Civil Engineering Department The
National Institute of Engineering Mysore-570
008 Mob 9342188467
Email gss_nie_at_yahoo.com
2
Portal frames
3
Learning out Come
  • Review of Design of Portal Frames
  • Design example Continued

4
  • INTRODUCTION
  • Step1 Design of slabs
  • Step2 Preliminary design of beams and columns
  • Step3 Analysis
  • Step4 Design of beams
  • Step5 Design of Columns
  • Step6 Design of footings

5
  • PROBLEM 2

6
  • PROBLEM 2

A portal frame hinged at base has following
data Spacing of portal frames 4m Height of
columns 4m Distance between column centers
10m Live load on roof 1.5 kN/m2 RCC slab
continuous over portal frames. Safe bearing
capacity of soil200 kN/m2 Adopt M-20 grade
concrete and Fe-415 steel. Design the slab,
portal frame and foundations and sketch the
details of reinforcements.
7
  • Data given
  • Spacing of frames 4m
  • Span of portal frame 10m
  • Height of columns 4m
  • Live load on roof 1.5 kN/m2
  • Concrete M20 grade
  • Steel Fe 415

8
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10
  • Step1Design of slab
  • Assume over all depth of slab as 120mm and
    effective depth as 100mm
  • Self weight of slab 0.12 x 24 2.88 kN/m2
  • Weight of roof finish 0.50 kN/m2 (assumed)
  • Ceiling finish 0.25 kN/m2 (assumed)
  • Total dead load wd 3.63 kN/m2
  • Live load wL 1.50 kN/m2 (Given in the data)
  • Maximum service load moment at interior support
    8.5 kN-m

11
  • Step1Design of slab (Contd)
  • MulimQlimbd2 (Qlim2.76)
  • 2.76 x 1000 x 1002 / 1 x 106 27.6 kN-m gt
    12.75 kN-m
  • From table 2 of SP16 pt0.384 Ast(0.384 x 1000
    x 100)/100 384 mm2
  • Spacing of 10 mm dia bars (78.54 x 1000)/384
    204.5 mm c/c
  • Provide 10 _at_ 200 c/c

12
  • Step1Design of slab (Contd)
  • Area of distribution steel Adist0.12 x 1000 x
    120 / 100 144 mm2
  • Spacing of 8 mm dia bars (50.26 x 1000)/144
    349 mm c/c
  • Provide 8 _at_ 340 c/c. Main and dist.
    reinforcement in the slab is shown in Fig

13
Step1Design of slab (Contd)
14
  • Step2 Preliminary design of beams and columns
  • Beam
  • Effective span 10m
  • Effective depth based on deflection criteria
    10000/13 769.23mm
  • Assume over all depth as 750 mm with effective
    depth 700mm, breadth b 450mm and column
    section equal to 450 mm x 600 mm.

15
  • Step3 Analysis
  • Load on frame
  • i) Load from slab (3.631.5) x 4 20.52 kN/m
  • ii) Self weight of rib of beam 0.45x0.63x24
    6.80 kN/m
  • Total ? 28.00 kN/m
  • Height of beam above hinge 40.1-075/2 3.72 m
  • The portal frame subjected to the udl considered
    for analysis is shown in Fig. 6.10

16
Step3 Analysis (Contd.)
17
  • Step3Analysis(Contd)
  • The moments in the portal frame hinged at the
    base and loaded as shown in Fig. is analised by
    moment distribution
  • IAB 450 x 6003/12 81 x 108 mm4, IBC 450 x
    7503/12 158.2 x 108 mm4
  • Stiffness Factor
  • KBA IAB / LAB 21.77 x 105 KBC IBC
    / LBC 15.8 x 105

18
  • Step3Analysis(Contd)
  • Distribution Factors
  • Fixed End Moments
  • MFAB MFBA MFCD MFDC 0
  • MFBC --233 kN-m and MFCB 233 kN-m

19
  • Step3Analysis(Contd) Moment Distribution Table

20
  • Step3Analysis(Contd) Bending Moment diagram

21
  • Step3Analysis(Contd) Design moments
  • Service load end moments MB156 kN-m,
  • Design end moments MuB1.5 x 156 234 kN-m,
  • Service load mid span moment in beam 28x102/8
    102 194 kN-m
  • Design mid span moment Mu1.5 x 194 291 kN-m
  • Maximum Working shear force (at B or C) in beam
    0.5 x 28 x 10 140kN
  • Design shear force Vu 1.5 x 140 210 kN

22
  • Step4Design of beams
  • The beam of an intermediate portal frame is
    designed. The mid span section of this beam is
    designed as a T-beam and the beam section at the
    ends are designed as rectangular section.
  • Design of T-section for Mid Span
  • Design moment Mu291 kN-m
  • Flange width bf
  • Here Lo0.7 x L 0.7 x 10 7m
  • bf 7/60.456x0.122.33m

23
  • Step4Design of T-beam
  • bf/bw5.2 and Df /d 0.17 Referring to table 58
    of SP16, the moment resistance factor is given by
    KT0.43,
  • MulimKT bwd2 fck 0.43 x 450 x 7002 x 20/1x106
    1896.3 kN-m gt Mu Safe
  • The reinforcement is computed using table 2 of
    SP16

24
  • Step4Design of T- beam
  • Mu/bd2 291 x 106/(450x7002)?1.3 for this
    pt0.392
  • Ast0.392 x 450x700/100 1234.8 mm2
  • No of 20 mm dia bar 1234.8/(?x202/4) 3.93
  • Hence 4 Nos. of 20 at bottom in the mid span

25
  • Step4Design of Rectangular beam
  • Design moment MuB234 kN-m
  • MuB/bd2 234x106/450x7002 ?1.1 From table 2 of
    SP16 pt0.327
  • Ast0.327 x 450 x 700 / 100 1030
  • No of 20 mm dia bar 1030/(?x202/4) 3.2
  • Hence 4 Nos. of 20 at the top near the ends for
    a distance of o.25 L 2.5m from face of the
    column as shown in Fig

26

Step4Design of beams Long. Section
27

Step4Design of beams Cross-Section
28
  • Check for Shear
  • Nominal shear stress
  • pt100x 1256/(450x700)0.39?0.4
  • Permissible stress for pt0.4 from table 19
    ?c0.432 lt ?v Hence shear reinforcement is
    required to be designed
  • Strength of concrete Vuc0.432 x 450 x 700/1000
    136 kN
  • Shear to be carried by steel Vus210-136 74 kN

29
  • Check for Shear
  • Nominal shear stress
  • pt100x 942/(400x600)0.39?0.4
  • Permissible stress for pt0.4 from table 19
    ?c0.432 lt ?v Hence shear reinforcement is
    required to be designed
  • Strength of concrete Vuc0.432 x 400 x 600/1000
    103 kN
  • Shear to be carried by steel Vus162-103 59 kN

30
  • Check for Shear
  • Spacing 2 legged 8 mm dia stirrup
  • sv
  • Two legged 8 stirrups are provided at 300 mm c/c
    (equal to maximum spacing)

31
  • Step5Design of Columns
  • Cross-section of column 450 mm x 600 mm
  • Ultimate axial load Pu1.5 x 140 210 kN (Axial
    load shear force in beam)
  • Ultimate moment Mu 1.5 x 156 234 kN-m (
    Maximum)
  • Assuming effective cover d 50 mm d/D ?0.1

32

33
  • Step5Design of Columns
  • Referring to chart 32 of SP16, p/fck0.04 p20 x
    0.04 0.8
  • Equal to Minimum percentage stipulated by
    IS456-2000 (0.8 )
  • Ast0.8x450x600/100 2160 mm2
  • No. of bars required 2160/314 6.8
  • Provide 8 bars of 20

34
  • Step5Design of Columns
  • 8mm diameter tie shall have pitch least of the
    following
  • Least lateral dimension 450 mm
  • 16 times diameter of main bar 320 mm
  • 48 times diameter of tie bar 384
  • 300mm
  • Provide 8 mm tie _at_ 300 mm c/c

35

600
450
8-20
Tie 8 _at_300 c/c
36
  • Step6Design of Hinges
  • At the hinge portion, concrete is under triaxial
    stress and can withstand higher permissible
    stress.
  • Permissible compressive stress in concrete at
    hinge 2x0.4fck 16 MPa
  • Factored thrust Pu210kN
  • Cross sectional area of hinge required
    210x103/1613125 mm2
  • Provide concrete area of 200 x100 (Area
    20000mm2) for the hinge

37
  • Step6Design of Hinges
  • Shear force at hinge Total moment in
    column/height 156/3.7242
  • Ultimate shear force 1.5x4263 kN
  • Inclination of bar with vertical ?
    tan-1(30/50) 31o
  • Ultimate shear force 0.87 fy Ast sin?
  • Provide 4-16 (Area804 mm2)

38
  • Step7Design of Footings
  • Load
  • Axial Working load on column 140 kN
  • Self weight of column 0.45 x 0.6 x3.72x 24
    24
  • Self weight of footing _at_10 16 kN
  • Total load 180 kN
  • Working moment at base 42 x 1 42 kN-m

39
  • Step6Design of Footings
  • Approximate area footing required Load on
    column/SBC
  • 180/200 0.9 m2
  • However the area provided shall be more than
    required to take care of effect of moment. The
    footing size shall be assumed to be 1mx2m (Area2
    m2)

40
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41
  • Step6Design of Footings
  • Maximum pressure qmaxP/AM/Z 180/26x42/1x22
    153 kN/m2
  • Minimum pressure qminP/A-M/Z 180/2-6x42/1x22
    27 kN/m2
  • Average pressure q (15327)/2 90 kN/m2
  • Bending moment at X-X 90 x 1 x 0.72/2 22
    kN-m
  • Factored moment Mu?33 kN-m

42
  • Step6Design of Footings
  • Over all depth shall be assumed as 300 mm and
    effective depth as 250 mm,
  • Corresponding percentage of steel from Table 2 of
    SP16 is pt 0.15 gt Minimum pt0.12

43
  • Step6Design of Footings
  • Area of steel per meter width of footing is
    Ast0.12x1000x250/100300 mm2
  • Spacing of 12 mm diameter bar 113x1000/300
    376 mm c/c
  • Provide 12 _at_ 300 c/c both ways

44
  • Step6Design of Footings
  • Length of punching influence plane ao 600250
    850 mm
  • Width of punching influence plane bo 450250
    700 mm
  • Punching shear Force Vpunch180-90x(0.85x0.7)1
    26.5 kN
  • Punching shear stress ?punchVpunch/(2x(aobo)d)
    126.5x103/(2x(850700)250) 0.16 MPa
  • Permissible shear stress 0.25?fck1.18 MPa gt
    ?punch Safe

45
  • Step6Design of Footings
  • Check for One Way Shear
  • Shear force at a distance d from face of column
  • V 90x1x0.45 40.5 kN
  • Shear stress ?v40.5x103/(1000x250)0.162 MPa
  • For pt0.15 , the permissible stress ?c 0.28
    (From table 19 of IS456-2000)
  • Details of reinforcement provided in footing is
    shown in Fig.

46

47

48
GOOD DAY
Dr. G.S.Suresh Civil Engineering Department The
National Institute of Engineering Mysore-570
008 Mob 9342188467
Email gss_nie_at_yahoo.com
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