Sump Revised Design

7/28/2019 Sump Revised Design

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RCC SUMP DESIGN

REFERENCE :1. IS 456-2000.2. IS 3370-2009 Part 1&2.3. SP-16 -1978.

DATA :Sump Size : 3.30m (L) X 2.80m(B) X 2.80m(H)Concrete Grade : For cover slab M20.

For Tank M25.Steel Grade : Fe 415

Unit weight of water : 10 KN/m3

Live Load(Vehicular traffic) for Cover slab 10 KN/m2

DESIGN:DESIGN OF COVER SLAB:

Slab size : 3.30m x 2.80mL/B =3.30/2.80= 1.18 =1.20< 2.0Hence the slab has to be designed as two way simply supported slab.d required =2800/25 = 112mm.However from deflection point of view provide D=150mmd=150-20-12/2= 124mm. > d required. O.k.Loads:Live Load(Assumed) = 10.0 KN/m2

Self weight 0.15x25 = 3.75 KN/m2

Finishing = 1.0KN/m2

Total Load = 14.75KN/m2

Effective span =2.80+0.124=2.924mThe slab has to be designed as two way simply supported slab usingcoefficient given in Table 27 of IS 456-2000.

Bending Moment Mx = xWl2 = 0.084x14.75 x2.9242= 10.59 KN.m.

Factored B.M. = 15.89 KN.m.

Bending Moment My = yWl2 = 0.059x14.75 x2.9242= 7.44 KN.m.

Factored B.M. = 11.16 KN.m.Max. B.M. Mu= 15.89KN.m

Mu.lim. =0.138 fck b d2

=0.138 x 20x 1000 x 1242

=42.44 KN.m > 15.89KN.mHence under reinforced section.K= Mu/b d2 =15.89 x106/1000 x 1242

=1.03From Table 2 of SP 16 pt =0.3046Ast= 0.3046 x 1000 x 124 =377.70 mm2


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100Using 12mm bars spacing = ast x 1000

Ast=113 x 1000 =299 mm377.70

Max spacing limit to 3d (3x124=372) or 300mm whichever is less.Provide 12mm dia bars at 150mm C/c. (Ast provided=753.33mm2)

Reinforcement along Long Diretion:Mini. Ast = 0.12 x 1000x 150 =180mm2

100Since B.M.=11.16 KN.m < 15.89KN.mProvide same reinforcement.Provide 12mm dia bars at 150mm C/c.

Max spacing limit to 5d (3x114=342) or 450mm whichever is less.Check for Deflection :

Actual span ratio = 2924/124 =23.58d

Actual pt required = 377.7 x 100 =0.30%1000x 124

Max. Permissible Span ratio from Chart 23 of SP16 =28.0 > 23.58d

Hence O.k.

8 tmt bars @ 200 c/c

SECTION OF TOP COVER SLAB


DESIGN OF WATER TANKDESIGN OF SIDE WALL:


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This has to be designed by Working Stress Method with the followingpermissible stresses to avoid leakage problem..Using M25 concrete andFe415 (HYSD) steel

cbc = 8.50N/mm2 st=150 N/mm2

Design Constants:

m=Modular ratio =280/3 cbc = 280 =10.98 =11.00

3x8.5

n = m cbc = 11 x 8.5 = 0.384

mcbc+ st 11x8.5+150

j= 1 n = 1- 0.384/3 = 0.872

3

K = cbc n j =1/2 x 8.50 x 0.384 x 0.872 =1.423

The water tank has to be designed for the following two cases.

1) Tank is full and no earthfill outside.2) Tank is empty and active earth pressure acting from outside.

Case 1: When Tank is full and no earth pressure outside


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Long Wall:Assume wall thickness D=230mm. d=230-30-10/2=195mm

Ph = w xH=10 x 2.80 =28.0 KN/m2

Cantilever moment M= (1/2x28.0 x 2.80) x2.80/2=54.88 KN.m

Ast = M/ st x j = 54.88 x 106 =2152 mm2

150x0.872x195

Using 20mm dia bars spacing required == 314 x 1000 = 146 mm

2152

Provide 20 mm bars at 140 mm C/c near inner face in verticaldirection.

Horizontal bars in Long wallSince long wall is predominantly acting as a cantilever, distribution steel isprovided & checked for axial Tension when tank is full without earthpressure from outside.Since the thickness of wall is more than 225mm, minimum % of steel to beprovided isMini. % of steel = 0.3 0.1( 230-100 ) = 0.263%

(450- 100 )

Ast = 0.263 x 230 x 1000 =604mm2

100Steel required ob each face =604/2=302 mm2

Using 10 mm bars spacing required = 78.5 x 1000 = 260 mm302

Provide 10mm bars at 150mm C/c inside the face.

Check for Direct Tension :

TL= w (H-h) B/2 = 10 x (2.80-1.0) 2.8/2= 22.20KN,Ast required = 22.50 x 103 = 168 mm2

150Distribution steel takes care of this Tensile forces .

Case 2: When Tank is empty

Ph =k 1 + wH where

K= 1- sin = 1-sin 30 =1/31+ sin 1+ sin 30

1s= s- w =18-10=8 KN/m2

Ph= (1/3 x 8x 2.80) +(10x2.80) =35.47KN/m2


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M=(1/2 x 35.47x HxH/3)=(1/2x 35.47 x 2.80x 2.80/3) =46.35 KN.m.

Depth of balanced section = sqrt M/k b = Sqrt 46.35 x 1061.423x1000

=180.48mmHowever provide D=230mm, d=230-30-20/2=190mm > 180.48mmAst required = M/ st j = 46.35 x 106

150 x0.872x 190=1865mm2

Using 20mm bars spacing required = 314 x 1000 =168mm1865

Provide 20mm bats at 140mm C/c near inner face of the wall tohave similar spacing as provided for outer wall.

DESIGN OF SHORT WALL :Vertical reinforcement :

Cantilever action height for lower portionh= H/4(2.80/4=0.70m) or 1m whichever is more =1m.When water tank is empty and outside soil is saturatedph=(1/3x8x2.80)+(10x2.80)=35.47KN.m2

M= 1/2x35.47x1.0x1.0/3 = 17.74KN.m

Ast = M = 17.74 x 106st x j 150x0.872x190

= 713.83mm2

Using 20mm bars spacing = 314 x 1000 =440mm

713.83Direct compression due to load on 1m wide long wallP= 35.47 x (2.80-1.0) x1.0 =63.85 KN.Concrete alone can resist if water tank is full and no earth fill.Ph= 10 x 2.80 =28.00KN/m2

M= x 28.0 x 1.0x 1.0/3 =4.67 KN.m .Ast= 4.67 x 106 = 188mm2

150x0.872x190Provide mini reinforcement in vertical direction which is 20mm at 140mmC/c

At Mid span :B.M. is half of 4.67/2 =2.34 KN.m


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Provide same reinforcement 20mm bars at 140mm C/c near outerface.

EARTH SIDE WATER (INSIDE)

SECTION OF WALL


DESIGN OF BASE SLAB:

Assume thickness of base slab =400mmd = 400-50-12/2=344mmHeight from base slab =2.80+0.40=3.20mUpward pressure when soil is saturated =10x3.20 =32.0 KN/m2

In bottom slab there is no projection.Effective span=2.80+0.23=3.03m

Downward Loads:Weight of top slab =0.15x3.76x 3.26x25 = 45.97KN.Weight of long wall =2x0.23x3.76x2.80x25 =121.07KNWeight of short wall =2x0.23x3.26x2.80x25 =104.97KNWeight of bottom slab =3.76x3.26x0.40x25 =122.57KNTotal Load = 394.58KN

Provide 150mmx 150mm haunches at junction. Provide junctionreinforcement 10mm bars at 150mm C/c.Self weight of slab directly get transmitted to soil.Net upward soil pressure=(10x3.20)- (0.4x1x1x25)

=32.0-10.0=22.0KN/m2

Bending moment:Considering net upward pressure B.M.=22.0x3.032/8= 29.95 KN.mConsidering weight of water alone B.M. =(10x2.80)x 3.032/8=38.12KN.mConsidering higher moment,Ast required = M = 38.12 x 106

st x j 150x0.872x344


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= 847mm2

Minimum Ast = 0.263 x 1000x400=1052mm2

100Providing reinforcement on both faces Ast on each face = 1052/2=526mm2

Using 16mm bars spacing = 201 x 1000= 237mm

847Provide 16mm bars at 150mm C/c

Distribution Steel:Since the thickness of wall is more than 225mm, minimum % of steel to beprovided isMini. % of steel = 0.3 0.1( 230-100 ) = 0.263%

(450- 100 )

Minimum Ast = 0.263 x 1000x400=1052mm2

100Ast on each face =1052/2= 526mm2

Using 12mm dia bars spacing = 113 x 1000=214.83mm526

Provide 12mm dia bars at 150mm C/c in longitudinal direction nearboth faces.

SECTION OF BASE SLAB



DESIGN ABSTRACTCover Slab:Slab Thickness =150mmMain rod : 12mm dia bars at 150mm C/c (alternate cranked) along shortdirection

12mm dia bars at 150mm C/c (alternate cranked) along Longdirection


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Side wall :Thickness : 230mmVertical rod inner and outer face : 20mm dia bars at 140mm C/cHorizontal rod : 10mm dia bars at 150mm C/c

Base Slab:

Slab Thickness : 400mmMain rod : 16mm Dia bars at 150mm C/c/Distributors : 12mm dia bars at 150mm C/c.

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Sump Revised Design