Top Circular Slab Design

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India Pavilion at World Expo 2010, Shangai, China

Top Circular Slab Design

Slab Design of Partially Fixed Circular Slab INPUT DATA :Diameter of circular slab

=

7350 mm

Grade of concrete

=

25 N/mm2

Grade of steel

=

415 N/mm2

Basic L/d ratio

20

Percentage of steel i.e pt

0.5 %

Modification Factor

1.5

Thickness of slab

=

I.S 456:2000 Cl 23.2.1

I.S 456:2000 Fig 4

245 mm

Provided depth of slab:--

250 .mm

Cover

=

25 mm

Assume the diameter of bar

=

12 mm

Effective depth of slab (d)

=

219 mm

Live load

=

5 kN/m2

Design Load

=

16.6875 kN/m2

Max. moment at center i.e Mr =

=

28.17 kN.m

Max. Shear

=

30.66328 kN/m

Effective depth of slab

=

90.36462 mm

Shear i.e v

=

0.140015 N/mm2

Minimum shear i.e Tc for M25

=

0.37 N/mm2

Calculation of Moments and Shear

Design of depth of slab 219 O.K.

0.140015 O.K.

Variation of Moments along the radius Radius at where the radial moment become 3000.625 mm Distance of Point of Contraflexu

=

674.3751 mm

Steel Calculation 1) Rectangular mesh for positive B.M ( MΦ & Mr ) in the central portion at the bottom Note : Mesh(Radial) reinforcement are provided in both ways at the bottom of slab.

(M/b*d*d)

=

0.587392

1

From IS:456 :2000 Table 19

India Pavilion at World Expo 2010, Shangai, China

Top Circular Slab Design

Percentage of steel i.e pt

=

0.2 %

Area of steel i.e Ast

=

438 mm2

Diameter of reinforcement

=

10 mm

Number of steel reinforcement

=

5.579618 Nos

Spacing of reinforcement

=

179.2237 mm

Spacing provided:-Provide

10

.mm dia at

SP:16 ( Depending of fck and fy)

Maximum limit of spacing is (3*d).

100 .mm 100 c/c spacing

2) Radial steel for negative B.M.(Mr ) at the ends placed on top of the slab (Provide in perpendicular dir.) Radius of the slab

=

Radial Moment (-ve) at the end

= -140.8594 kN.m

(M/b*d*d)

=

Percentage of steel i.e pt

=

0.94 %

Area of steel i.e Ast

=

2058.6 mm2

Diameter of reinforcement

=

12 mm

Number of steel reinforcement

=

18.21125 Nos

Spacing of reinforcement

=

54.9111 mm

Spacing provided:--

7.35 M

2.936958

Maximum limit of spacing is (3*d) .

100 .mm

Curtailment of reinforcement beyond point o 818.3751 mm

Provide

SP:16 ( Depending of fck and fy)

12

mmdia at

100

I.S 456:2000 Cl.26.2.3.1

mm c/c spacing

3) Circumferential steel for negative B.M.(Mθ ) at the ends placed on the bottom of the slab(Provide in perpendicular dir.) Note : Provide circumferential steel for development length at the ends on the bottom of the slab. Diameter of reinforcement

=

10 mm

Development length ( Ld )

=

818.3751 mm

SP:16 Table 65

Spacing required

=

224.0297 mm

Maximum limit of spacing is (3*d) .

Spacing provided:--

=

100 .mm

Number of rings

=

4.463694 Nos

Provide

10

mmdia at

100

mm c/c spacing ( 6 Nos.)

4) Circumferential steel for negative B.M.Mθ ) at the ends placed on the top of the slab(Provide in perpendicular dir.) Note : These circumferential steel are provided same as given in the above (3rd case) calculation.

2

India Pavilion at World Expo 2010, Shangai, China

Top Circular Slab Design

Number of rings

=

4.463694 Nos

Spacing required

=

224.0297 mm

Spacing provided:--

100 .mm

Development length ( Ld ) Provide

Maximum limit of spacing is (3*d) .

10

= mmdia at

818.3751 mm 100

SP:16 Table 65

mm c/c spacing

3

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