ECCENTRIC FOOTING BY WS.pdf

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DESIGN Of FOOTING FOR THE APPROACH SLAB PIER DESIGN Of FOOTING FOR THE APPROACH SLAB PIER DATA:

DATA: S

Saaffe e bbeeaarriinng g ccaappaacciitty y oof f ssooiill==qq== 1155 tt//ssqq..mm V

Veerrttiiccaal l llooaad d oon n tthhe e ccoolluummnn==PP== 6655..88 tt H

Hoorriizzoonnttaal l FFoorrcce e iin n x x ddiirreeccttiioonn==HHxx 00..0000t Lt LAA== 0 m0 m H

Hoorriizzoonnttaal l ffoorrcce e iin n z z ddiirreeccttiioonn==HHzz== 00..0000t Lt LAA== 0 m0 m M

Moommeennt t iin n xx--ddiirreeccttiioonn==MMxx 00..00 TT--MM M

Moommeennt t iin n z z ddiirrccttiioonn==MMzz== 4422..1166 TT--MM T

Toottaal l MMoommeennt t IIn n XX--ddiirreeccttiioonn==MMxx++HHz z x x YY11== 00..0 T0 T--MM T

Toottaal l MMoommeennt t iin n ZZ--ddiirreeccttiioonn==MMzz++HHx x x x YY22== 4422..1166 TT--MM

The moment due to temperature & braking force is assumed to the abutments a small The moment due to temperature & braking force is assumed to the abutments a small moments due to min. eccentricity is assumed

moments due to min. eccentricity is assumed C Coolluummnnhheeiigghhtt 55 mm M M _X_X Z Z Z Z X X XX M M ZZ P P H H_Z_Z H H_X_X

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u

unniit t wweeiigghht t oof f susub b ssttrraattaa 22..44 tt//ccuumm.. Angle of internal f

Angle of internal f riction of the soilriction of the soil 2020 deg.deg. G

Grraaddeeooff ccoonnccrreettee MM 2200

G

Grraaddeeooff sttes eeell FFee 441155

P

Peerrmmiissssiibblle e ssttrreennggtth h oof f ccoonnccrreettee 7700 kkgg//ssqq..ccmm P

Peerrmmiissssiibblle e ssttrreennggtth h oof f sstteeeell 22330000 kkgg//ssqq..ccmm U

Unniit t wweeiigghht t oof f ccoonnccrreettee 22..55 tt//ccuumm.. K

K22== 00..4499

C

Coohheessiivve e rreessiissttaanncce e oof f ssooiill== 2200 tt//ssqq..mm s

siizze e oof f ccoolluummn n [ [ a a x x b b ]] aa== 223300 mmmm b

b== 554400 mmmm Depth of foundation for the above value of

Depth of foundation for the above value of == 113388..11 mm

column reinforcement column reinforcement ties ties pier pier Footing Footing a a b b L L B B

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P

Peerrmmiissssiibblle e ssttrreesss s ffoor r ppuunncchhiinng g sshheeaarr== 110 k0 kgg//ssqq..ccmm D

Deepptthh aatt tthhee eeddggeess 3300 ccmm

COMPUTATION: COMPUTATION: M

Miinniimmuum m ddeepptth h oof f ffoouunnddaattiioonn 11..550022 mm M

M..RR. . ppaarraammeetteerrss mm== 1133..333333 k k== 00..228899 j= j= 0.9040.904 Q Q== 99..113311 S

Seellf f wweeiigghht t oof f ffoooottiinngg 1100 % % W W == 66..558800 tt T

Toottaal l wweeiigghht t oon n ffoooottiinngg PP==((11++1100%%))xxWW++MM//ee== 8800..113311 tt R

Reeqquuiirreed d aarreea a oof f ffoooottiinngg ==PP//qq== AA== 55..334422 ssqq..mm L Leennggtthhooff ffoooottiinngg LL== 11..550088 mm s saay y AA== 22..66000 m0 m Width of footing Width of footing BB== 44..220000 mm IIxxxx== 1166..005522 mm44 IIzzzz== 66..115522 mm44

Weight of soil on the footing Weight of soil on the footing

N

Neet t uuppwwaarrd d ffoorrccee PPdd 66..002266 tt//ssqq..mm S Sttrreeees s dduue e tto o MXMX ffxx 00..000000 tt//ssqq..mm S Sttrreeees s dduue e tto o MzMz ffzz 88..991100 tt//ssqq..mm ff11== --22..888855 tt//ssqq..mm ff22== 1144..993366 tt//ssqq..mm ff33== 1144..993366 tt//ssqq..mm

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<SBC, Okay <SBC, Okay =2.60m =2.60m =0.69m =0.69m =0.54m=0.54m =4.20m =4.20m 30cm 30cm 1.185 1.185 =0.23m =0.23m

STRESS DISTRIBUTION AT THE BASE STRESS DISTRIBUTION AT THE BASE

BENDING MOMENT: BENDING MOMENT:

ll11==((LL--aa)) 22..3377 ll11==((LL--aa))//22 11..11885 m5 m ll22==((BB--bb)) 33..6666 ll22==((BB--bb))//22 11..883 m3 m M

M1 1 bbe e mmoommeennt t nnoorrmmaal l tto o bb--ssiiddee MM11== 44..223311 tt--mm M

M2 2 bbe e mmoommeennt t nnoorrmmaal l tto o aa--ssiiddee MM22== 55..111166 tt--mm m maaxx.. BB..MM== M3M3== 1111..004455 tt--mm DEPTH OF FOOTING: DEPTH OF FOOTING: 5 52266..225500 mmmm d d L L B B (L-a)/2-d (L-a)/2-d

 



          B B bb B B bb Width Width -5.0 -5.0 0.0 0.0 5.0 5.0 10.0 10.0 15.0 15.0 20.0 20.0 0 0..0000 22..6600 S S T T R R E E S S S S ( ( t t / / s s q q . . m m ) ) BASE W

BASE W IDTH(P-QIDTH(P-Q))

P P QQ R R S S 0.0 0.0 5.0 5.0 10.0 10.0 15.0 15.0 20.0 20.0 0 0..0000 44..2200 S S T T R R E E S S S S ( ( t t / / s s q q . . m m ) ) BASE WIDTH(Q-R) BASE WIDTH(Q-R) -5.0 -5.0 0.0 0.0 5.0 5.0 10.0 10.0 15.0 15.0 20.0 20.0 0 0..0000 22..6600 S S T T R R E E S S S S ( ( t t / / s s q q . . m m ) ) BASE WIDTH(R-S) BASE WIDTH(R-S) -4.0 -4.0 -3.0 -3.0 -2.0 -2.0 -1.0 -1.0 0.0 0.0 0 0..0000 44..2200 S S T T R R E E S S S S ( ( t t / / s s q q . . m m ) ) BASE WI BASE WI DTH(P-DTH(P-S)S)

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D Deepptth h bbaasseed d oon n MM11 dd11== 2299..667722 ccmm D Deepptth h bbaasseed d oon n MM22 dd22== 3322..663311 ccmm D Deepptth h bbaasseed d oon n MM33 4477..994433 ccmm C Chhoooosse e mmaaxxiimmuum m dd== 4477..994433 ccmm Say Say dd== 5500..000000 ccmm

Depth from shear consideration: Depth from shear consideration:

D

Diia a oof f tthhe e bbaarr 1122 mmmm C

Clleeaar r ccoovveerr 5500 mmmm Effect

Effective ive depth depth at at edgesedges(considering bars spaced at rt.angles)(considering bars spaced at rt.angles) de=de= 224444 mmmm

o

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i] One way shear i] One way shear

V

V== 1177..333366 tt E

Effffeeccttiivve e ddeepptth h oof f ffoooottiinng g aat t d d ffrroom m ccoolluummn n ffaaccee==dd''== 3399..119988 ccmm T

Toop p wwiiddtth h oof f tthhe e sseeccttiioon n aat t tthhe e ppooiinntt== 220088..443 c3 cmm D

Deepptth h oof f nneeuuttrraal l axaxiiss==kkdd''== 1111..3311 ccmm W

Wiiddtth h oof f sseeccttiioon n aat t NN..AA..==bb''== 224477..8866 ccmm



_v= _v= 17.84317.843 t/sq.mt/sq.m k k== 11..000000 a asstt 44..007711 ssqq..ccmm % % oof f sstteeeell 00..001199 ssqq..ccmm 2 288.0.04455 t/t/ssqq.m.m



_v

<< okayokay

Weight of soil on the footing Weight of soil on the footing

De

Depth for ppth for p unching shunching sh ear=ear=

104.00 104.00 73.00 73.00 L L _c _c _c _c B B

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L Lbb== 110044..000000 ccmm A= A= 10.16110.161 sq.msq.m V V''== 6611..222255 tt b boo==22((bb++dd))++22((aa++dd)) 22..550000 mm Effective depth at critical section=

Effective depth at critical section=dodo == 2255..000000 ccmm F

Frroom m ffaacce e oof f ccoolluummnn== 4444..559999 ccmm shear stress=

shear stress=_v_v 54.91254.912 t/sq.mt/sq.m Permissible shear stress=

Permissible shear stress= kk_s_s=0.5+=0.5+cc



cc=b/a==b/a= 2.3482.348

T

Thheerreeffoorre e kkss== 22..884488 If ks>1.5, then ks is restricted to 1 If ks>1.5, then ks is restricted to 1 T

Thheerreeffoorre e kkss== 11..000000 7

711.5.55544 t/t/ssqq.m.m k

k_s_s_c_c 71.55471.554 t/sq.mt/sq.m O

Ovveerraalll l ddeepptth h oof f ffoooottiinng g aassssuummiinng g ddiia a oof f bbaarr== 1122 556688..000000 mmmm O

Ovveer r aalll l ddeepptth h aaddoopptteedd== 660000..000000 mmmm Available effective dep

Available effective depth=th= 532.000532.000 mmmm CALCULATION OF AREA OF STEEL:

CALCULATION OF AREA OF STEEL: Ast1=area of st

Ast1=area of steel for M1 eel for M1 == 10.010.0 sq.cmsq.cm M

Miinniimmuum m aarreea a oof f sstteeeell== 99 ssqq..ccmm D Diiaaooff bbaarr == 1122 mmmm Area Area 1.131.13 sq.cmsq.cm N Noo.. ooff bbaarrss == 1100 Ast2= area of

Ast2= area of steel for M2steel for M2 == 19.0619.06 sq.cmsq.cm D Diiaaooff bbaarr == 1122 mmmm Area Area 1.131.13 sq.cmsq.cm     ck ck c c 00..1616 f f ''  

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L Ldd

CHECK FOR TRANSFER OF LOAD AT THE BASE: CHECK FOR TRANSFER OF LOAD AT THE BASE:

As per code the bearing pressure

As per code the bearing pressure _cbr_cbr> .25 f > .25 f _ck_ck sqrt(A1/A2)sqrt(A1/A2) A1(based on side slope of

A1(based on side slope of== 22 H:1VH:1V A1 A1 == 8.648.64 sq.msq.m A2 A2 == 0.120.12 sq.msq.m A1/A2 A1/A2 == 69.5969.59 8.34 8.34 As per code

As per code if if T

Thheerreeffoorree 22..0000 T

Thheerreeffoorre e bbeeaarriinng g pprreessssuurree == 11000000..00 tt//ssqq..mm Actual bearing pressure

Actual bearing pressure == 529.79529.79 t/sq.mt/sq.m safe safe   2 2 1 1 A A A A 22 a d o p t a d o p t 22 22 11 _{t h e n}_{t h e n} A A A A     2 2 1 1 A A A A

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Length of bars available on either face or Length of bars available on either face or criti

critical cal sectiosection n for for bendinbending= g= 1.6671.667 mm L Ldd== 7766..6677  0 0..9922 mm SAFE SAFE T

Thheerreeffoorre e pprroovviidde e hhooook k eeqquuaal l tto o a a LLeennggtthh== mmmm OKAY

OKAY

Area resisting this=2(a+b)xd=

Area resisting this=2(a+b)xd= 154154 d d sq.cmsq.cm

T

Thheerreeffoorre e dd== 3399..775577 ccmm d

d== 5500..00000 c0 cmm Adopt the dept

Adopt the depth=h= 50.00050.000 cmcm

Ca

Calculatio olculatio o f revised depth f revised depth if s_v>s_cif s_v>s_c Area=

Area= 2.8772.877 sq.msq.m VV''== 1177..33336 t6 t breadth of footing=

breadth of footing= 115544..000000 ccmm Depth at this section=

Depth at this section= 4411..556611 ccmm E

Effffeeccttiivve e ddeepptthh== 3322..556611 ccmm S

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iii] check for two way shear(Punching shear) iii] check for two way shear(Punching shear)

Net shear Net shear p

peerriimmeetteer r oof f ccrriittiiccaal l sseeccttiioon bn boo== 33..666688 mm D

Diist st frfrom om ededge ge fofor r crcriititicacal l sesectctioion(n(alalonong g LsLspapan)n)== 91919.9.000000 D

Diist st frfrom om ededge ge fofor cr crriititicacal sl secectitionon((alalonongBgBLsLspapan)n) 15156464.0.00000 Area Area 3.8603.860 sq.msq.m D Deepptth h aat t tthhe e ppooiinntt 445555..110055 S Shheeaar r aat t tthhe e ccrriittiiccaal l sseeccttiioonn== 2233..225588 tt  _v'= _v'= 1133.9.93322 t/t/ssqq.m.m p

peerrmmiissssiibblle e sshheeaar r ssttrreessss== kks s x x ss__cc'' == kks s x x ssqqrrtt((ffcckk)) w

whheerre e kkss== 11..000000 T

Thheerreeffoorre e ppeerrmmiissssiibblle e sshheeaar r ssttrreessss== 7700..116666 tt//ssqq..mm  _v' _v' << kkss..ss__cc'' ""ookkaayy""

By Limit

By Limit state Mstate Method:ethod: M

Moommeennt t oof f rreessiissttaanncce e wwiitth h rreessppeecct t tto o ccoonnccrreettee== 22..7755 bbdd^^22 F

Faaccttoorreed d mmoommeenntt==MMuu== 116655..667711 kkNN--mm E

Effffeeccttiivve e ddeepptthh==dd== 441100 mmmm E

Effffeeccttiivve e ddeepptth h aas s ppeer r wwoorrkkiinng g ssttrreessss== 448800 mmmm Depth provided is okay

Depth provided is okay N

Neeuuttrraal l aaxxiis s ddeepptth h rraattiioo==xxuu//dd== 00..447799 Area of steel f

Area of steel f or balanced section=Ast2=or balanced section=Ast2= 975.29975.29 mmmm22 Area of steel provided=

Area of steel provided= 1905.71 mm1905.71 mm22

M

Miinn aarreeaa ooff sstteeeell== 990000 mmmm22 Hence area provided is okay