ECCENTRIC FOOTING BY WS.pdf

T IT L E:

DESIGNED BY:

ECCENTRIC FOOTING

CHECK ED

DESIGN Of FOOTING FOR THE APPROACH SLAB PIER DATA: Saf e bearing capacity of soil=q= 15 t/sq.m Vertical load on the column=P= 65.8 t Horizontal Force in x direction=Hx 0.00t LA L A= 0m Horizontal f orce in z direction=Hz= 0.00t LA L A= 0m Moment in x-direction=Mx 0.0 T-M Moment in z dirction=Mz= 42.16 T-M Total Moment In X-direction=Mx+Hz x Y1= 0.0 TT-M Total Moment in Z-direction=Mz+Hx x Y2= 42.16 T-M The moment due to temperature & braking force is assumed to the abutments a small moments due to min. eccentricity is assumed Column height 5m

P

HX

X

Z X

HZ

M X Z

M Z

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T IT L E:

DESIGNED BY:

ECCENTRIC FOOTING

unit weight of sub strata  Angle of internal f riction of the soil Grade of concrete Grade of steel Permissible strength of concrete Permissible strength of steel Unit weight of concrete K2 = Cohesive resistance of soil= size of column [ a x b ]

a= 230 b= 540 Depth of foundation for the above value of  =

CHECK ED

2.4 20 M Fe 70 2300 2.5 0 .4 9 20

t/cum. deg. 20 415 kg/sq.cm kg/sq.cm t/cum. t/sq.m

138.1

m

mm mm

column reinforcement ties B

pier 

b a

Footing L

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ratio =b/a= Permissible stress f or punching shear= Depth at the edges COMPUTATION: Minimum depth of f oundation M.R. parameters

Self weight of footing Total weight on f ooting Required area of footing Length of f ooting Width of footing Ixx= Izz=

CHECK ED

2.348 10 kg kg/sq.cm 30 cm

m= k=  j= Q=

10 % W = P=(1+10%)xW +M/e= =P/q= A= L= s ay A= B=

1.502 13.333 0.289 0.904 9.131 6.580 80.131 5.342 1.508 2.600 4.200 16.052 6.152

m

t t sq.m m m m m4 m4

Weight of soil on the footing

Net upward force Strees due to MX Strees due to Mz f 1= f 2= f 3= f 4=

Pd fx fz

6.026 t/sq.m 0.000 t/sq.m 8.910 t/sq.m -2.885 14.936 14.936 -2.885

t/sq.m t/sq.m t/sq.m t/sq.m

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1.5, then ks is restricted to 1 T' heref ore ks= 1.000      0.16 f  c ck  71.55 .554 t/s t/sq.m ksc 71.554 t/sq.m Overall depth of footing assuming dia of bar= 12 568.000 mm Over all depth adopted= 600.000 mm  Available effective depth= dep th= 532.000 mm CALCULATION OF AREA OF STEEL:  Ast1=area of steel st eel for M1 Minimum area of steel= Dia of bar  Area No . o f b ar s  Ast2= area of steel for M2 Dia of bar  Area No . o f b ar s

= = = = = =

10.0 9 12 1.13 10

sq.cm sq.cm mm sq.cm

19.06 sq.cm 12 mm 1.13 sq.cm 18

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Ld

CHECK FOR TRANSFER OF LOAD AT THE BASE:  As per code the bearing pressure cbr  > .25 f ck sqrt(A1/A2)  A1(based on side slope of= of = 2 H:1V  A1 =  A2 =  A1/A2 =  A 1

 As per code if 

 A 1  A 2



2

then

Therefore Theref ore bearing pressure  Actual bearing pressure

8.34



 A 2

8.64 sq.m 0.12 sq.m 69.59

adopt2

 A 1  A

2.00



2

= =

1000.0 t/sq.m 529.79 t/sq.m safe

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T IT L E:

DESIGNED BY:

ECCENTRIC FOOTING

CHECK ED

Check Check f or development length: Length of bars available on either face or  critical critical section section for bending= bending= L d=

1.667 m 76.67  0.92 m

SAFE Theref ore provide hook equal to a Length=

 Area resisting this=2(a+b)xd= Therefore d= d=  Adopt the depth= dept h=

mm OKAY

154 39.757 50.000 50.000

d sq.cm cm cm cm cm

Calculatio Calculatio o f revised depth if s_v>s_c  Area= 2.877 sq.m breadth of footing= Depth at this section= Ef fective depth= Shear stress=

V '=

17.336 154.000 41.561 32.561 3.825

t cm cm cm kg/sq.cm OKAY

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T IT L E:

DESIGNED BY:

ECCENTRIC FOOTING

CHECK ED

iii] check for two way shear(Punching shear) Net shear  perimeter of critical section bo b o= 3.668 Dist from from edge edge for for cri critica ticall sect sectio ion( n(al alon ong g Lspa Lspan) n)= = 919. 919.00 000 0 Dist from from edge edge for for cr critica ticall sec secti tion on((alon alongB gBLs Lspa pan) n) 1564 1564.0 .000 00  Area 3.860 Depth at the point 455.105 Shear at the critical section= 23.258  _v'= 13.93 .932 permissible shear stress= ks x s_c' = ks x sqrt(fck) where ks= 1.000 Theref ore permissible shear stress= 70.166  _v' <

ks.s_c'

m

sq.m t t/s t/sq.m

t/sq.m "okay"

By Limit state Method: Method: Moment of resistance with respect to concrete= Factored moment=Mu= Ef fective depth=d= Ef fective depth as per working stress= Depth provided is okay Neutral axis depth ratio=xu/d=  Area of steel f or balanced section=Ast2=  Area of steel provided= Min area of steel= Hence area provided is okay

2.75 165.671 410 480

bd^2 kN-m mm mm

0.479 2

975.29 mm 2 1905.71 mm 2 900 mm

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