Bangalore Water Supply & Sewerage Project (II) Design & Cost Estimates

Civil Contract S1c: K&C Valley STP Page No. 1 of 4

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

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

1.0 M Below EGL 12 T/Sqm

2.0 M Below EGL 16 T/Sqm

3.0 M Below EGL 18 T/Sqm

4.0 M Below EGL 24 T/Sqm

Assume for Depth

6.0 M Below EGL 35 T/Sqm

B) Design of The wall:-

Wall top Level= 880.5 M

Base slab level= 872 M

Wall Height = 8.5 M

Wall Th. provided at base t= 0.3 M

Wall Th. provided at span t= 0.3 M

Tank Diameter D= 5.90 M

HxH/Dxt is adopted for Bending Moment= 40.82

HxH/Dxt is adopted for Ring Tension= 40.82

As the values are greater than 20 , hoop forces are citical in the wall.

Vertically provided nominal steel

For 300 Th. Section -----Y12-140C/C B.F

Empty condion will produce hoop compression . Not Critical

C) Design of Wall For Hoop Forces :-

Tank Full Condition is Critical :-

Top 0.0 H to 0.3 H

Bangalore Water Supply & Sewerage Project (II) Design & Cost Estimates

Civil Contract S1c: K&C Valley STP Page No. 2 of 4

Hoop force in Top 0.0 H to 0.3 H= coeff x w x h x r = T 246.0 Kn

Tu=T x1.5 369.0 Kn

Permissble stress in steel=fst 435.0 Mpa

=Tu/fst = Steel required 8.5 Sqcm

Steel on each face 4.2 Sqcm

Adopting 12

Area of Each Bar 113.10

Spacing Reqd 266.67

Provide a Spacing of 125.00 mm

Ast Provided on Each Face 12 mm

Spacing 125.00

Ast Provided = 904.78 Sq mm

Top 0.3 H to 0.5 H

Hoop force in Top 0.3 H to 0.5 H=0.55x8.39x9.81x12.4 = T 245.99 Kn

Tu=T x1.5 368.98 Kn

Permissble stress in steel=fst 435.00 Mpa

Steel required 8.48 Sqcm

Steel on each face 4.24 Sqcn

Adopting 16

Area of Each Bar 201.06

Spacing Reqd 474.08 mm

Provide a Spacing of 135.00

Ast Provided = 1489.35 Sq mm

0.5 H to 0.9 H

Hoop force in 0.5 H to 0.9 H=0.72x8.39x12.4x9.81 = T 245.99 Kn

Tu=T x1.5 368.98 Kn

Permissble stress in steel=fst 435.00 Mpa

Steel required 8.48 Sqcm

Steel on each face 4.24 Sqcn

Adopting 12

Area of Each Bar 113.10

Spacing Reqd 266.67 mm

Provide a Spacing of 150.00 mm

Ast Provided = 753.98 Sq mm

mm2

mm2

mm2

Bangalore Water Supply & Sewerage Project (II) Design & Cost Estimates

Civil Contract S1c: K&C Valley STP Page No. 3 of 4

D) Design of Foundation for the Wall :-

Net safe bearing Capacity at founding level 35 T/Sqm

say 350 Kn/sqm

Assume

Weight of Reinforced Concrete 25

Weight of Plain Cement Concrete 24

Weight of Soil 18

Weight of Water 9.81

Factor of Safety reqd. 1.20

Height of Walls 8.5 m

Height of Soil Fill 0 m

Height of Original Soil level to Foundation level 7 m

Inner Dimension of Slab/Tank (Diamter) 5.90 m

Wall Thickess (At top) 0.3 m

Wall Thickess (At bottom) 0.30 m

Thicknes of Bottom Slab 0.4 m

Thicknes of Top Slab 0 m

Thickness of PCC at base 0.15 m

External projection of Footing 0.30 m

Water table encountered fom top of existing ground 8.5 m

Average Wall Thickness = 0.3 m

Outer Dimension of Tank at TOP (Diamter) 6.5 m

Outer Dimension of Tank at BOTTOM (Diamter) 6.5 m

Dimension of Tank BOTTOM Slab (Diamter) 7.1 m

Area of base slab 39.59 m2

kN/m3

kN/m3

kN/m3

kN/m3

Bangalore Water Supply & Sewerage Project (II) Design & Cost Estimates

Civil Contract S1c: K&C Valley STP Page No. 4 of 4

Area at bottom of outer edge of walls 33.18 m2

Bottom of excavated level from top of existing `ground 7.40 m

E) Design of The Base Slab:-

Weight of Walls 1241.71 kN

Total Load = 1241.71

Upward Reaction due to Net Load 31.36

Total Upward Reaction ( Due to DL ) = 32.00

Bending Moment calculations for base slab based on IS 3370 Coefficients

From IS 3370 part 4

Radius of Tank ------------ 2.95

Maximum Bending Moment at Support - 34.81 kN-m

Maximum Bending Moment at Span - 20.89 kN-m

(Stress forconcrete =2.0MPA)

D rqd for uncraked section 32.32 cms

<<< 40 Cms

F) CALCULATION OF CRACKWIDTH FOR DIRECT TENSION ONLY

Axial Tension…………………………………………………………………… 245.99 KN

Width of Section………………………………………………………………… 1000.00 mm

Overall Member Depth………………………………………………………… 300.00 mm

Axial cover to Steel………………………………………………………… 60.00 mm

Modular Ratio……………………………………………………………………… 7.30

Bar Dia Assumed 12.00 mm

Bar Spacing assumed ……………………………………………………… 150.00 mm

Area of Steel ………………………………………………………………… 753.98 mm2

Modulus of Elasticity of Steel …………………………………………… 200000.00 N/mm2

Apparent Strain ……………………………………………………………… 0.00

Stiffness Factor for concrete between cracks …………………………………… 0.00

em 0.00

acr 93.90 mm

Crack width …………………………………………………………………… -0.10 mm

Check for Shear for Circular Tanks

Dia of Tank 2.5 m

Height of Tank 5 m

Thickness of Wall at bottom 0.25 m

40.00

Unit Weight of Water 9.81

Shear Force at base of wall 122.625 kN

Shear Force at distance of d from Base 116.49 kN

Shear Force at distance of 2d from Base 110.3625 kN

Co-eff Triangular Load - Fixed Base 0.127

Shear Force 14.79

Shear Stress Tu = Vu/bd 0.08

Steel Provided in Tension Zone

Dia 12 mm

Spacing of bars 100 mm

Area Provided = 1130.97

Percentage of Steel Provided 0.42

Allowable Shear Stress 0.00

kN/m2

kN/m2

Bending Moment = Co-efficient * p * R2

m

H2/Dt Ratio

kN/m3

N/mm2

mm2

N/mm2