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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
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
• 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)
• 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
• 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
• 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
• 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
• 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