Design and drawing of RC Structures CV61

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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
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Portal frames
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Learning out Come

• Review of Design of Portal Frames
• Design example Continued

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• 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

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• PROBLEM 2

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• 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.
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• 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

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• 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

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• 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

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• 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

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Step1Design of slab (Contd)
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• 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.

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• 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

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Step3 Analysis (Contd.)
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• 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

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• Step3Analysis(Contd)

• Distribution Factors
• Fixed End Moments
• MFAB MFBA MFCD MFDC 0
• MFBC --233 kN-m and MFCB 233 kN-m

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• Step3Analysis(Contd) Moment Distribution Table

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• Step3Analysis(Contd) Bending Moment diagram

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• 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

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• 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

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• 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

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• 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

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• 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

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Step4Design of beams Long. Section
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Step4Design of beams Cross-Section
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• 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

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• 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

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• 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)

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• 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

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• 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

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• 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

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600
450
8-20
Tie 8 _at_300 c/c
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• 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

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• 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)

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

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• 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)

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• 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

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• 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

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• 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

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• 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

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• 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.

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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