1

A) Introduction:-

Two numbers of circular thickeners have been provided as per

the process requirement. The wall of the thickener is designed as

circular wall as per the coefficents in IS 3370-part IV.

The wall is designed as hinged at base for hoop forces and span

B.M in the wall . On inner face of the wall steel is provided for

100% fixity condition.

B) Geo-technical Investigation & Soil Data Adopted in Design:-

One number of Bore hole BH10 has been done at thickener

location. Average EGL at this location is 595.5 . Refusal strata

is met at depth of 1.5 M , N value =112 ( 594 M level).

Proposed FGL in this area is 593.0 M . The founadtion is provided

500 mm below FGL on the refulsal strata.

The bearing capacity as per the soil report is as follows :-

1.5 M below EGL 25 T/Sqm

2.5 M below EGL 30T/Sqm

For hard Rock Bearing pressure of 60 T/sqm is adopted.

Note:- The bearing capacities in the table are Net safe bearing

Capacities of the soil and gross bearing capacity at founding level

are adopted as follows:-

Gross Bearing Capacity = Net Bearing Capacity + 1.6 x Depth of Foundation.

( Soil load from Existing Ground level to Finished ground level

or above due to plinth filling will be treated as load , with soil

weight of 2.0 T/Cum)

For the Back fill soil following soil properties are adopted:-

Soil Properties adopted in the design:- ( Back Fill material)

Soil weight T/Cum

2

j Angle of Internal Friction 30 Degree

( For cantilever walls) Coefficient Active pressure 0.33 Ka

( For propped / circular Walls) Pressure at Rest 0.5 Kr

( For Computation of Loads) Weight of Soil 20

Submerged Soil Weight 10

(For stability against Uplift) Weight of Soil 16

(For stability against Uplift) Submerged Soil Weight 8

Subsoil Water level Not Present

Force resistance from soil due to friction is computed as per the

following equation.

F= 2 / 3 ( tan ( )) x W

W= Vertical Load on the Slab / Footing

2/3xtan ( ) =0.384

C)

All water retaining structure are designed as per the provisions

in IS 3370-Part II - 2009 with controlled crack width of 0.1mm

as per the specifications. The water level for the design shall be

adopted as follows :-

For strength calculations water shall be taken up to top of the wall

assuming all outlets are blocked . For serviceability limit state

condition water level is adopted at working top liquid level or the

overflow level as appropriate ( refer cl.4.2 of IS 3370-II -2009)

Strength Calculations will be carried out using limit state design

as per IS456-2000 with load factor of 1.5 .

For empty condition soil level will be adopted as applicable.

Non Liquid Retaining Structures and Buildings :-

All non liquid retaining structures like foundations and columns of

Kn/M3

Kn/M3

Kn/M3

Kn/M3

Liquid Retaining Structures:-

j

j

3

elevated tanks and Buildings will be designed as per IS 456-2000.

D) Design Idealization , Load Conditions and Load combinations:-

I) Design Idealization :-

Rectangular tank's walls will be designed as rectangular plates for

the boundary conditions as applicable using MOODY'S charts.

Permissible stresses will be adopted as per the material retained.

The wall will be treated as fixed at base & common edges with

adjacent wall panels as applicable. Walls with aspect ratio

greater than 3 , will be designed as one way as per boundary

conditions . For walls of rectangular tanks the direct horizontal

tension and bending action will be adopted as per IS 3370-partII

Circular tanks Clarifiers , thickeners etc. will be

designed for HOOP forces and Bending Moment .

The foundation of the wall will provide nominal fixity to the

wall , for foundation design 50% fixity is adopted.

In the wall vertical span steel and hoop steel is provided for the

hinged base condition . However on the inner face of the wall

vertical steel at base is provided for fixed base condition.

F) Specific Design Requirement as per tender Specifications.

E1) Materials for Construction:-

I) Plain Concrete as Mud mat :-

PCC as mud mat below RCC , 100mm Thick. M10

1000 gauge polythene sheet will be provided

as sliding layer below base slab and raft slab

of water retaining structures.

II) Concrete Grades for RCC Structures :-

Liquid Retaining Structure M30

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Buildings / non Liquid retaining Structures M25

All structural concrete will be with aggregates 40mm down for

Footings and base slab and with 20mm down aggregates for all

water retaining and other structures. For screed concrete 12.5mm

down size aggregates will be used.

III) Steel as Reinforcement for the Concrete:-

For Water retaining structures : CRS Fe 500Grade.

( Steel with corrosion resistant Characteristics)

E2) Minimum Thickness of Reinforced Concrete:-

Following minimum thicknesses of the members will be provided

Walls Liquid retaining Structures 250.00 mm

Bottom Slab liquid retaining structures 250.00 mm

Walls Foundations ( at base slab & wall junction250.00 mm

Roof slab of Liquid retaining structures 200.00 mm

Launder base slab & wall 150 mm

Shell roof 100 mm

Floors , roof slab , walkways , canopy slabs 125 mm

Walls of cable & Pipe trenches 200 mm

Under ground Pits etc. 200 mm

Footings at edge 200 mm

Footing at column face 300 mm

Columns:- Width 300 mm

Depth 300 mm

Beams:- Width 230 mm

Depth 300 mm

Parapets , Chajjas etc. 100 mm

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Preacst Trench covers 75 mm

E3) Minimum Cover to any Reinforcement:-

Slabs:- Free face 30 mm

Face in contact with Soil 40 mm

Beams:- Top & Bottom 40 mm

Side / face in Contact with Soil 40 mm

Columns & Pedestals Super Structure 50 mm

Sub. Structure 50 mm

Foundations :- Bottom , Top 50 mm

Sides 50 mm

Retaining Walls , Basement & Pit Walls:-

Face in Contact with Soil 40 mm

Free face 30 mm

Liquid retaining Structures

Face in contact with liquid 50 mm

Face in contact with Soil 50 mm

Free face 50 mm

E4)

Major Foundations 10 mm

Block Foundations :- Main bar 10 mm

Dist. Steel 8 mm

Columns & Pedestals Main bar 12 mm

Links 8 mm

Minimum Bar Diameter of Reinforcement bars :-

6

Beams:- Main bar 12 mm

Stirrups 8 mm

Slabs & Base Slabs :- Main bar 10 mm

Dist. Steel 10 mm

Walls & Wall Foundations :- Main bar 10 mm

Dist. Steel 8 mm

Other Minor elements 8 mm

shell roof :- Main bar 10 mm

Dist. Steel 8 mm

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F) Design of The wall of the Thickener :-

Typical Wall Section

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F1) Design of main wall:-

Wall top Level= 597.5 M

Base slab level= 593 M

Wall Height = H= 4.5 M

Wall Th. provided at base t= 0.25 M

Wall Th. provided at span t= 0.25 M

Tank Diameter D= 19.5 M

HxH/Dxt is adopted = 4.15

Design of wall For Bending Moment :-

Base B.M Tank Full case :- Coefficient as per IS 3370= 0.026

=9.81x4.5 Water pressure at base Triang. 44.145 Kn/Sqm

Refer table 10 of IS 3370-Part IV for Coefficient

B.M= 0.026x44.145x4.5x4.5 23.24234 Kn-M

Ultimate B.M = Mu=1.5 M 34.86 Kn-M

D ( Cms )= 25 d= 19.5 Cms

Mu/(bx d x d) 0.916858

Refer Sp16 , Table 4 Pt ( required ) 0.23 %

Ast= 4.485 Sqcm

Provided on Inner Face Y10-175 C/C

Base B.M for Tank Empty Case:- Not critical

Refer table 13 of IS 3370-Part IV for Coefficient

Maximum Span B.M in wall for Hinged Case=0.0118xwxHxHxH 10.54845 Kn-M

D ( Cms )= 25 d= 19.5 Cms

Mu/(bx d x d) 0.416112

Refer Sp16 , Table 4 Pt ( required ) 0.105 %

Ast= 2.0475 Sqcm

Provided on outer face Y10-175 C/C

Check for shear force in the wall at base :- Adopted as for fixed base

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Refer table 11 of IS 3370-Part IV

Coefficient for shear 0.23

Shear force = V 45.69008 Kn

(Note : Shear will be lesser at critical section " d " from base slab face.)

Ultimate shear=1.5 x V 68.53511 Kn

D ( Cms )= 25 d= 19.5 Cms

Vu/(b x d) 0.351462

Refer Sp16 , Table 61 Pt ( required ) 0.23 %

Ast= 4.485 Sqcm

Provided on Inner Face Y10-175 C/C

Mimimum Steel Required :-

Mimimum Pt 0.35 %

Surface zone =25/2= 12.5 Cms

Ast= 4.375 Sqcm

Provided Y10-175 C/C B.F

10

Check for Crack width:-

As crack width is << 0.1mm section is OK.

CRACK WIDTH FOR FLEXURE EFFECT

Grade of Concrete Used (fcu) = N/mm230

Grade of Steel Used (fy) = N/mm2500

Area of Reinforcement " As " = mm2448

Width of Section b = mm 1000

Depth of Section h = mm 250

Effective Depth of Section " d " = mm 195

Minimum Cover to Tension Reinforcement " CO " = mm 50

Maximum Bar Spacing " S " = mm 175

Bar Dia = mm 10

" acr " = (((S/2)^2 + (CO + DIA/2 )^2)^(1/2)-DIA/2) = mm 98.35

Distance From the Point Considered to the Surface of Nearest Longitudinal barApplied Service Moment " Ms " = KNm 23.20

CALCULATION :Moduli of Elasticity of Concrete " Ec " = 5000x ( sqrt(fcu) ) = KN/mm2

27.39

Moduli of Elasticity of Steel " Es " = KN/mm2200.00

Modular Ratio " " = (Es/Ec) = 7.30

"" = As/bd = 0.00230 = 0.02

Depth of Neutral Axis, " X " = d^0.5)-1) = mm 32.60Lever arm " Z " = ( d - X/3) = mm 184.13

Reinforcement Stress " fs " = Ms/(As*Z) = N/mm2281.24

Concrete Stress " fc " = (fs*As)/(0.5*b*X) = N/mm27.73

Strain at Soffit of Concrete Slab "" = (fs/Es)*(h-X)/(d-X) = 0.00188

Strain due to stiffening effect of Concrete between the Cracks " " = 0.00162

2 = b . (h-X)2/(3.Es.As.(d-X)) for Crack Width of 0.2mm N/A

2 = 1.5 .b . (h-X)2/(3.Es.As.(d-X)) for Crack Width of 0.1mm used

Average Strain for Calculation of Crack width "m " = 1 - 2

= 0.00026

Calculated Crack Width , " W " = 3.acr.m(1+2(acr-CO)/(h-X))

Calculated Crack Width " W " = mm 0.053

c

fc

X 0.5 . fc . b. XN.A

h dZ

As s fs . As

fs

S

= =

CO acr

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Design of Wall For Hoop Forces :-

Tank Full Condition is Critical :- Refer table 12 of IS 3370-Part IV

Hoop force in Top 0.0 H to 0.3 H=0.367x4.5x9.75x9.81 = T 157.9618 Kn

Tu=T x1.5 236.9428 Kn

=0.87x500 Permissble stress in steel=fst 435 Mpa

=Tu/fst Steel required 5.44696 Sqcm

Steel on each face 2.7234801 Sqcn

Provided minimum steel Y10-175 C/C B.Faces

Hoop force in 0.3 H to 0.8 H=0.58x4.5x9.75x9.81 = T 249.64 Kn

Tu=T x1.5 374.46 Kn

=0.87x500 Permissble stress in steel=fst 435 Mpa

=Tu/fst Steel required 8.608275 Sqcm

Steel on each face 4.304137 Sqcn

Provided minimum steel Y10-175C/C B.Faces

Below 0.8H steel is provided nominal Y10-175 C/c B.Faces.

No craking of the section.

CALCULATION OF CRACKWIDTH FOR DIRECT TENSION ONLY

Axial Tension T KN 250Width of Section b mm 1000Overall Member Depth h mm 250Axial cover to Steel a mm 60Modular Ratio alpha 7.3Bar Dia Assumed mm 10Bar Spacing assumed s mm 175Area of Steel As mm2 897Modulus of Elasticity of Steel Es N/mm2 200000Apparent Strain e1 0.00139353Stiffness Factor for concrete between cracks e2 0.001393534

em 0.00000000acr mm 104.0011468Crack width w mm 0.0000000

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F2) Design of the launder:-

Vertical wall of the launder :- Wall Top level 597 M

Base Slab level 596.4 M

Wall height 0.6 M

B.M as cantilever 0.35316 Kn-M

=((0.35x100000x6/(1000x150^2) Bending stress developed 0.093 MPA

Nominal

Ast=( fst=130,d=7.5) 0.4261357 Sqcm

Min steel =0.35x15 5.25 Sqcm

Provided Y10-145 C/C

Provided above minimum steel Horizontally also.

Design of Base Slab of the launder:-

Base slab is designed as cantilever from the main wall.

B.M due to base slab from vertical wall

Self Load of the wall=V 2.25 KN

B.M at wall face=0.375*V 0.84375 Kn-M

B.M due to load on the base slab :-

Self Load Base slab ( av 0.2th) 0.50625 Kn-M

PCC fill ( max =0.2 th) 0.216 Kn-M

( ht above PCC) Water Load max.(0.4 m ) 0.28122 Kn-M

Total B.M = 1.84722 Kn-M

Axial force 0.7848 KN

D provided 25 Cms

=Mx1e6/(0.85x130xdx100) Ast ( B.M , fst=130,d=19.5) 0.857278 sqcm

= Tx1e3/(130/100/2) Ast axial force each face 0.030185 Sqcm

Total steel 0.887463 Sqcm

Minimum steel =0.35x12.5 4.375 Sqcm

Provided Y10-175 C/C

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Distribution steel Y8-110 C/C T & B

F3) Design of Foundation for the Wall :-

Net safe bearing Capacity at founding level 25 T/Sqm

say 250 Kn/sqm

Loading :-

Dead load of the wall:-

Wall height provided 4.50 M

Thickness provided 0.25 M

Load / Meter 28.13 Kn/m

Dead load from the launder:-

Wall Load 2.81 Kn/M

Base slab + Water+ Screed 4.12 Kn/M

Total Launder Load 6.93 Kn/M

Self load Footing :-

Average thickness 0.25 M

Base slab width provided 1.45 M

Load / Meter 9.06 Kn/M

Total Dead load effect = V d.l. 44.12 Kn/M

say 45.00 Kn/M

Footing width provided 1.45 M

Base pressure developed 31.03 Kn/Sqm

Soil Load effect :-

Soil load on external projection:-

Soil height 0.1 M

Projection width 0.6 M

Load / M @ 20Kn/Cum 1.2 Kn/M

Soil + Slab Load on Internal Projection:- not present in this case

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Soil height 0 M

Projection width 0 M

Load / M @ 20Kn/Cum 0 T/M

Slab Load 0 T/M

Total load on inner Projection 0.00

Total soil Load V s.l 1.20 Kn/M

say 1.20 Kn/M

B.M at footing center line 0.51 kn-M

2.28 Kn/sqm

Additional Base pressure inside -0.63 Kn/sqm

( Out side) Maximum base pressure in combination Dead L 33.32 Kn/sqm

(Inside) Maximum base pressure in combination Dead L 30.41 Kn/sqm

Water Load effect :-

Water height 4.50

Slab projection 0.60

Load /M = 26.49

B.M due to water load 11.26

Refer page 8 B.M due to water pressure 23.24

50 % fixity B.M =23.24/2 11.62

Design B.M -0.36

Base pressure developed

Inside in combination D.L 48.27 Kn/sqm

Outside in combination D.L 50.34 Kn/sqm

=48.27-0.63 Inside in combination D.L+S.L 47.64 Kn/sqm

=50.34+2.28 Outside in combination D.L+SL 52.62 Kn/sqm

Effect of the Bridge Load :-

Reaction from Bridge 150 Kn

Load after dispersion through

Additional Base pressure out side

M

M

Kn/m

T-M

Kn-M

Kn-M

Kn-M

15

wall at 45 degree=150/(2x4.8) 15.63 Kn/M

Load/ sqm= 10.78 K/sqm

Maximum Base pressure 63.40 Kn/sqm

<<<250Kn/sqm OK

Maximum Footing Projection 0.6 M

(Pr=63.4-slab load - soil load) B.M in Footing 9.926319 kn-M

(Sress forconcrete =2.0MPA) D rqd for uncraked section 17.25658 cms

<<< 30 Cms

d=30-5-0.5 , Ast ( Fst=130) 4.61 Sqcm

Minimum Pt=0.35x15 5.25 Sqcm

Provided Top & bottom Y10-350+Y12-350C/C

Distribution steel Y10-145 C/C T & B

F4) Design of The Base Slab:-

Base Slab Provided 25.00

Base slab is designed as slab on grade and nominal steel is

provided as per IS 3370-Part II Pt rqd= 0.35

Surface zone 12.50

Ast= 4.38 Sqcm

Provided in top part as D < 300 mm Provided Y10-175C/C at top

Refer fig to IS 3370-Part 2

Cms

%

cms

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F5) Seismic Load Effect :- Seismic load is adopted as per IS 1893-2002

Refer IS-1893 -2000 Part 1

Sa/g= 2.5

Damping 5

Z= 0.16

R= 3

I= 1.5

Ah= 0.1000

Horizontal coefficients are computed as per IS 1893-1984

( Referred as Part 2 of code is not published , refer page 2 of

IS 1893-part 1)

R= 9.75 M

H= 4 M Service Condition

For maximum force Cos ( Phi) =, y= h

Pw=0.35x9.81 3.4335 Kn/sqm

As above increase is lesser than the free board , Seismic case not critical

%

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G) Design of Staircase:- Staircase is provided with stringer Beam

=1.2x(3.739+2.188

+1.2+5)+0.3x0.45x25/0.8

Steel provided 3 nos-Y16 T & B

Stps Y8-150 C/C 2 legged.

DESIGN OF STAIR CASE USING ULTIMATE DESIGN

STAI R CASE MARKED ST1

Span of Stair case Lx 4.500 MStair case Width Stb 1.200 MRiser R 0.175 MTread T 0.250 MWaist Slab Thickness provided D 0.120 MStringer beam Size B 0.300 M

D 0.450 MLoading:-Dead Load waist slab 3.739 Kn/ sqmSelf load Step 2.188 Kn/ sqmFinish Load ( 50Th) 1.200 Kn/ sqmLive Load 5.000 Kn/ sqmUDL on Beam 18.759

Total Load W 18.759 Kn/m

Maximum Bending Moment M 47.483 Kn-m (WxLxL/ 8)

Design Of sectionClear cover to R/ F provided Cl 40.000 mmBar diameter Bd 16.000 mmEff ective depth (stp 10mm) Deff . 392.000 mmConcrete Grade Fck 30.000 MpaSteel Grade Fy 500.000 MpaUltimate bending Moment Mx1.5 71.224 Kn-mMu/ FckxBxdeff Xdeff ) 0.052 Sing R/ FArea of Steel rqd. 5.221 SqcmArea of steel provided 6.000 sqcm

Check for deflection

Steel Stress ratio 252.354 Mpa( refer Fig 4 I S456)Pt. provided 0.510 %ageModification factor 1.000Continuity f actor 1.000Eff ective depth Required 225.000 ok

Design For Shear:-S.F 42.207 KnVu 63.311 knVc 58.800 KnVs 4.511 Kn

Y-8 2Legged Sv 3152.797 mm

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Design of column below staircase :-

Provided 300 mm diameter column .

Maximum load on the column 84.6 Kn

As load on column is nominal provided nominal 0.8 % steel

Ast= 5.652 Sqcm

Provided 6 Nos Y12

Links Y8-150C/C

( As the bearing Capacity of the soil 25 T/sqm , area rquired for

above load is only 0.34 Sqm , Provided nominal footing )