footing biaxial

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NUCLEAR POWER CORPORATION OF INDIA LTD.

127744024.xls

DESIGN OF BI-AXIAL ISOLATED RCC FOOTING (IS 456, 2000)

Building Name

Footing Number:

Node number

COLUMN/PEDESTAL

Length (l, dim. || Z axis ) = 700 mmBreadth (b, dim. || X axis) = 600 mm

Height of pedestal = 1 m Breadth 6.5 m

Weight of pedestal/column = 10.50 KN

FOOTING

Foot length (L, dim. || Z axis) = 6.75 m

Foot Breadth (B, dim. || X axis) = 6.5 m

Thickness of footing (t) = 750 mm

Clear cover to Reinforcement = 75 mm

Main bar dia of footing = 16 mm

Effective depth of footing = 667 mm Length 6.75 m

Selfweight of the footing = 822.66 KN

Area of Footing(A) = 43.88

Sect mod of foot about Z axis (Zz) = 47.53

Sec mod of foot about X axis (Zx) = 49.36

MATERIALS OF CONSTRUCTION

20

415

CHECK FOR GROSS BEARING PRESSURE

1650

Safe gross bearing pr. = 1702.25 (net pr. + depth of foot * soil unit wt)

215Axial load from output (P1) = 721.07 KN

200 KN-m

2000 KN-m

Depth of top of foot. from ground = 2 m

Unit wt of soil = 19

Weight of soil retained above foot = 1651.29 KN

P = (P1+soil+pedestal+foot selfwt) = 3205.52 KN

Maximum bearing pressure = 117.79

Minimum bearing pressure = 28.33

Hence footing is safe against max gross bearing pr.

DESIGN FORCESFactored load comb. no. 18

100 KN

100 KN-m

5 KN-m

( Pu/Area+ Muz/Zz + Mux/Zx) = 4.48

( Pu/Area - Muz/Zz - Mux/Zx) = 0.07

Design of footing is done using above maximum effective soil pressure

m2

m3

m3

Grade of concrete fck

= N/mm2

Grade of steel fy= N/mm2

SafeNET bearing pressure = KN/m2

KN/m2

Unfactored load case number =

Moment about Z axis (Mz) =

Moment about X axis (Mx) =

KN/m3

KN/m2

KN/m2

Axial load:(Pu) =

Moment about Z axis (Muz

) =

Moment about X axis (Mux

) =

Maximum effective soil pressure pe max

KN/m2

Minimum effective soil pressure pe min

KN/m2

P

A

My

Zy

Mx

Zx

globalZ

globalX

globalX

globalZ

Footing Dimensions

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NUCLEAR POWER CORPORATION OF INDIA LTD.

127744024.xls

CALCULATION FOR BOTTOM STEEL

20.52 KN-m per meter

Mulimit = 1228.80 KN-m per meter

The section is singly reinforced

Hence, Ast = 85.468Min Ast = 800.400 (0.12 % for slab, cl 26.5.2.1)

Spacing = 251.20 mm (considering max of above two calculated values of Ast)

pt provided = 0.12 %

Hence provide 16 mm dia bar @ 251 mm c/c parellel to length of footing ( || to Z)

19.51 KN-m per meter

Calc. Ast = 81.272 The section is singly reinforced

Min Ast = 800.4 (0.12 % for slab, cl 26.5.2.1)

Spacing = 251.20 mm (considering max of above two calculated values of Ast)

pt provided = 0.12 %

Hence provide 16 mm dia bar @ 251 mm c/c parellel to breadth of footing ( || to X)

Arrangement of bottom reinforcement as per above design is shown below

16 mm dia bar @ 251 mm c/c

16 mm dia bar @ 251 mm c/c

1 1

Footing Length 6750 mm Breadth 6500 mm

Sec 1-1

1367 600

1267

L1

a a

Z Z

N1 N1

a a

L2 L2

2358

L1 Breadth 6500 mm

700

Footing Length 6750 mm 2283

PLAN

Mu about X1 X1 = ( pe max x length2/2)=

mm2

mm2

Mu about N1 N1 = ( pe max x length2/2)=

mm2

mm2

X1 X

X1 X

Ast=

0.5fck

fy [1 1

4.6Mu

fckbd2 ] bd

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NUCLEAR POWER CORPORATION OF INDIA LTD.

127744024.xls

CHECK FOR ONE WAY SHEAR :

One way shear at critical section L1- L1

Distance of critical sec. from edge of footing = 2.36 m

Shear force Vs =pe max x 2.358 x 1m width of footing = 10.574 KN

Shear stress 0.016

0.26

tv < tc hence O.K.

One way shear at critical section L2- L2

Distance of critical sec. from edge of footing = 2.28 m

Shear force Vs =pe max x 2.283 x 1m width of footing = 10.238 KN

Shear stress 0.015

0.26

tv < tc hence O.K.

CHECK FOR TWO WAY SHEAR

Ref. cl 34.2.4 and cl.31.6.3 of IS 456 : 2000

1.54 >1

1

1.12

1.12

Shear force Vs = 4.484 ( 6.75 x 6.5 - 1.367 x 1.267) = 188.99 KN

Length of critical section = 2 x ( 1367 + 1267) = 5268 mm

Area of the critical section (length of critical sec x eff. d ) = 3513756

0.054

tv < allowable hence O.K.

tv= Vs/bd = N/mm2

tc

= N/mm2

tv= Vs/bd = N/mm2

tc

= N/mm2

Allowable shear stress tv allowable

= ks

tc

ks= ( 0.5 + bc) =

Hence, ks=

tc= 0.25 (fck)0.5 = N/mm2

tv allowable

= ks

x c

= N/mm2

mm2

Hence shear stress v= N/mm2

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DESIGN OF BI-AXIAL ISOLATED RCC FOOTING (IS 456, 2000)

Project name

Building name

Breadth 6.5 m

Length 6.75 m

Column/Pedestal Footing size

mm mm m KN m m mm

500 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

700 600 0 0 6.75 6.5 750

Length (l,dim. || Z

axis )

Breadth(b, dim. ||

X axis)

Height ofPedestal

Weight ofpedestal

Footlength (L,

dim. || Zaxis)

FootBreadth

(B, dim. ||X axis)

Thicknessof footing

(t)

globalZ

globalX

globalX

globalZ

Footing Dimensions

Z and X axis are ass

as two horizontal Gloaxis of building.

Hence, input the

dimensions of footin

easily b y inputing folength parallel to glo

and footing breadthparallel to global X.

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16 mm dia

16 mm dia

1

Footing Length 6

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Sec 1-1

1167

L1

a a

Z

N1

a a

L2 L2

2458L1

500

Foot ing Length 6750 mm PLAN

X1 X

X1 X

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NUCLEAR POWER CORPORATION OF INDIA LTD.

127744024.xls

DESIGN OF BI-AXIAL ISOLATED RCC FOOTING (IS 456, 2000)

Building Name

Footing Number:

Node number

COLUMN

Length (l, dim. || Z axis ) = 700 mm

Breadth (b, dim. || X axis) = 600 mm

Height of pedestal = 1 m Breadth 3 m

Weight of pedestal/column = 10.50 KN

FOOTING

Foot length (L, dim. || Z axis) = 5 m

Foot Breadth (B, dim. || X axis) = 3 m

Thickness of footing (t) = 750 mm

Clear cover to Reinforcement = 75 mm

Main bar dia of footing = 16 mm

Effective depth of footing = 667 mm Length 5 m

Selfweight of the footing = 281.25 KN

Area of Footing(A) = 15.00Sect mod of foot about Z axis (Zz) = 7.50

Sec mod of foot about X axis (Zx) = 12.50

MATERIALS OF CONSTRUCTION

20

415

CHECK FOR GROSS BEARING PRESSURE

1650

Safe gross bearing pr. = 1702.25 (net pr. + depth of foot * soil unit wt)

215

Axial load from output (P1) = 10 KN

500KN-m

450KN-m

Depth of top of foot. from ground = 2 m

Unit wt of soil = 19

Weight of soil retained above foot = 554.04 KN

P = (P1+soil+pedestal+foot selfwt) = 855.79 KN

Maximum bearing pressure = 159.72

Minimum bearing pressure = -45.61

Recalculation of max pressure done below as min pressure is negative.

Recalculated max bearing press. = 170.76 Max bearing pressure is safe

Minimum bearing pressure = 0

DESIGN FORCES

Factored load comb. no. 18

150 KN

150 KN-m

150 KN-m

( Pu/Area+ Muz/Zz + Mux/Zx) = 42.00

( Pu/Area - Muz/Zz - Mux/Zx) = -22.00

Recalculation of maximum effective pressure done below as min pressure is negative.

75.15

0

m

2

m3

m3

Grade of concrete fck

= N/mm2

Grade of steel fy= N/mm2

SafeNET bearing pressure = KN/m2

KN/m2

Unfactored load case number =

Moment about Z axis (Mz) =

Moment about X axis (Mx) =

KN/m3

KN/m2

KN/m2

KN/m2

KN/m2

Axial load:(Pu) =

Moment about Z axis (Muz

) =

Moment about X axis (Mux

) =

Maximum effective soil pressure pe max

KN/m2

Minimum effective soil pressure pe min

KN/m2

Maximum effective soil pressure pe max

KN/m2

Minimum effective soil pressure pe min KN/m2

P

A

My

Zy

Mx

Zx

globalZ

globalX

globalX

globalZ

Footing Dimensions

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NUCLEAR POWER CORPORATION OF INDIA LTD.

127744024.xls

CALCULATION FOR BOTTOM STEEL

173.68 KN-m per meter

Mulimit = 1228.80 KN-m per meter

The section is singly reinforced

Hence, Ast = 738.53Min Ast = 800.40 (0.12 % for slab, cl 26.5.2.1)

Spacing = 251.20 mm (considering max of above two calculated values of Ast)

pt prov