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