Design Data: OK

Capacity of Tank = 300 m3

Grade of Concrete = 30 N / mm2
Grade of Steel = 415 N / mm2
S.B.C. = 113.75 kN /m2
Basic Wind Speed = 39 m/sec2
No. of Supporting Columns = 6 Nos.
Height of Staging Above G.L = 15 m
Diameter of Column = 500 mm
Seismic Zone = Zone V
Nominal Cover( on water face) = 45 mm ( In General Except Foundation)
Nominal Cover in Found n
= 50 mm
Permissible Stresses :
sst (water face) = 150 N / mm2 (Face near to water)
sst(awayfrom water) = 190 N / mm2 (Face away from water)
scbc = 10 N / mm2 ( For Strength Calculation)
scc = 8 N / mm2 ( For Strength Calculation)
sdt(concrete) = 1.5 N / mm2 (Perm. Stress in direct tension)
m = 9
sst (columns) = 230 N / mm2 (not in contact with water)
scbt = 2 N / mm2 (Perm. Stress in bending tension)
Design Constants
k = 0.38
j = 0.88
Q = 1.64
Dimensions of the Tank:
Diameter of Cylindrical Portion D = 10.6 m
Diameter of bottom Ring Beam dr = 8.6 m
Height of Conical Dome hc = 1m
Rise of Top Dome ht = 2m
Rise of Bottom dome hb = 1.4 m
Radius of Top Dome = 8.023 m
Radius of Bottom Dome = 7.304 m
(Top ring beam) f1 = ASIN(5.3 / 8.02) x(180/PI) = 41.35 0
(Bottom ring beam) f2 =ASIN (4.3 / 7.304 ) x (180/PI) = 36.07 0
(Conical Dome) fo = ATAN (6.3 / 1 ) x 180/PI = 45.00 0
Height of Water Column Required = 3.10 m
Capacity of Tank = 304.11 m3
Provided Height OK
Break up of Capacity Calculation
Content in Cylindrical Portion = 3.14 / 4 x 10.6 ^2 x 3.1 = 273.57 m3
Content in Conical shell ( Deducting Bottom dome)
= 3.14 x 1 / 12 x ( 10.6 ^ 2 + 8.6 ^ 2 + ( 10.6 x 8.6 ) - ( 3.14
x ( 1.4 ^ 2 ) ) / 3 ) x (3 x 7.304 - 1.4 ) = 30.55 m3
Invert level of outlet pipe above top of ring beam = 0.30 m
Dead Storage = 3.14 x 8.6 x 0.5 x 0.3 x 0.6 = 2.43 m3
Freeboard = 0.30 m
Total Height of Cylindrical Portion = 3.4 m
Trignometric Ratios
sinf1 = 0.66 cosf1 = 0.75
sinf2 = 0.59 cosf2 = 0.81
sinf0 = 0.71 cosf0 = 0.71
Design of Top Dome:
Thickness of Dome = 150 mm
Self weight of Dome = (150 / 1000 ) x25) = 3.75 kN/m2
Live Load = 1.00 kN/m2
Total Load = 4.75 kN/m2
Meridional Thrust at Edges = (4.75 x 8.02)/( 1 + 0.75) = 21.77 kN/m
Meridional Stress = (21.77 x 1000 ) / ( 150x 1000 ) = 0.145 N/mm2 Safe
Maximum Hoop Stress occurs at centre
Hoop Stress =(0.5 x(4.75x1000x8.02)/(150/1000) = 0.127 N/mm2 Safe
Since the stresses are within the limits , provide nominal Reinforcement @ 0.3%
Both in Meridional & Hoop Direction
Area of Steel Required :
As = ( 0.3 / 100 ) x 150x 1000 = 450 mm2
Hence provide 10 mm f bars at 150 c/c as meridional and hoop reinforcement
So Area of steel provided = 523.60 mm2 OK
Design of Top Ring Beam B1:
Horizotal component
Tension tending of Meridional
to rupture the Thrust P1 = 16340.24 N/m
beam (due to meridional thrust) = (16340.24x5.3 ) = 86603.27 N

Thrust due to Water = 9800 x 10.6 x 0.55 x 0.5 = 28567 N

Total tension tending to rupture the beam
= ( 86603.266 + 28567 ) = 115170.27 N
Area of steel required = 115170.27 / 150 = 767.80 mm2
Provide 20 mm f bars 12 Nos
And 12 mm f bars 0 Nos
So Area of steel Provided = 3769.91 provided steel ok
Final Design done after continuity analysis
Cross sectional area of the ring beam is given by = 46620.89
Width of ring beam = 550 mm
Depth of ring beam = 84.77 mm
Provide ring beam of size
B = 550 mm
D = 550 mm Provided dimensions OK
Stress Developed in The Section
sdt developed
= 0.26 < 1.5 OK
Shear Reinforcement:
Provide 10 mm dia 2 Legged Stirrups
Minimum Spacing Required = ( 3.14 x 0.25 x10 ^ 2 x 2 ) x 0.87 x415 ) / (0.4 x 550 ) = 257.79
Spacing of shear reinforcement = 370 or 257.79 mm whichever is less
So provide shear reinforcement at = 250 mm C/c
Design of Cylindrical Wall :
In the Membrane analysis ,the tank wall is assumed to be free at top and and bottom.
Maximum hoop tension occurs at the base of the wall , its magnitude being given by
P = 9800 x 3.4 x 10.6 x 0.5 = 176596 N/m height
Area of hoop steel required Ash = 1177.31 mm 2
per meter height at base
Providing ring on both faces , so steel on each face = 588.65 mm2
Spacing of 16 mm dia ring required 342 mm
So provide 16 mm dia ring at 95 mm C/c OK
The wall is designed for the total hoop gw H D/ 2 and checked for the methodology given in IS 3370 : 1967 ( Part IV)
So Ash provided = 2116.44 mm2 ( on Each face)
Permissible tensile stress = 1.5 N/mm2
For the composite section thickness of wall required.
t = 83.87 mm
Provide thckness of wall at top = 200 mm
Provide thickness of wall at bottom = 400 mm
Average thickness = 300 mm
Vertical Reinf.
% of Distribution Steel required = 0.24 %
(Considering Average thickness)
Area of distribution steel required = 728.57 mm2
Area of steel on each face = 364.29 mm2
Spacing of 10 mm dia bars required 215.60 mm
On water face provide 10 mm dia bars at 200 mm C/c OK
Away from water face 10 mm dia bars at 180 mm C/c
Area of steel provided = 392.70 mm2 on water face
= 436.33 mm2 away from water face
Chart showing requirement of hoop reinf. at different levels along the wall height
Distance from the top Hoop Tension Area of hoop steel Bar dia Steel on faces Spacing of hoop steel required
on each face
%h m N/m mm2 mm Both / One mm c/c
0 0 0.00 0 16 both -
0.2 0.68 35319.20 235.46 16 both 1707.81
0.4 1.36 70638.40 470.92 16 both 853.91
0.6 2.04 105957.60 706.38 16 both 569.27
0.8 2.72 141276.80 941.85 16 both 426.95
1 3.4 176596.00 1177.31 16 both 341.56
Reinforcement Scheme
 Distance from top Spacing of Hoop Steel Area of hoop steel provided
%h m Provided mm2
0 0 250 1608.50 O.K.
0.2 0.68 250 1608.50 O.K.
0.4 1.36 200 2010.62 O.K.
0.6 2.04 150 2680.83 O.K.
0.8 2.72 115 3496.73 O.K.
1 3.4 95 4232.88 O.K.
 Checking The Section for Crack Resistance
Permissible Stress in the Composite Section = 1.5 N/mm2
Stresses in the composite section at the base
ss = 176596 / (1000 x 400 ) + ( 8 x 4232.88) 0.41 N/mm2 Provided Thickness O.K.
Checking of Stresses at Various Levels of Tank Wall
Distance from Top Hoop Tension Thickness Reinf. Stress
%h m Provided Developed
0 0 0 200 1608.50 0
0.2 0.68 35319.2 240 1608.50 0.14
0.4 1.36 70638.4 280 2010.62 0.24
0.6 2.04 105957.6 320 2680.83 0.31
0.8 2.72 141276.8 360 3496.73 0.36
1 3.4 176596 400 4232.88 0.41
Calculation of Bending moments and Hoop Tension in Cylindrical Wall as per IS 3370 : 1967 (Part IV)
The wall is considered to be fixed at base and free at top. H2 / (D x t) = 3.635
Depth from top of wall Coeff. for Hoop Tension Coeff. for B.M 150
%H Actual level (m) hoop tension (N) 150
0.0H 0.000 0.019 3423.80 0.0000 150.00
0.1H 0.340 0.121 21804.20 0.0001 150.00
0.2H 0.680 0.236 42527.20 0.0004 150.00
0.3H 1.020 0.344 61988.80 0.0009 150.00
0.4H 1.360 0.439 79107.80 150.0000 150.00
0.5H 1.700 0.500 90100.00 150.0000 150.00
0.6H 2.040 0.507 91361.40 150.0000 150.00
0.7H 2.380 0.439 79107.80 150.0000 150.00
0.8H 2.720 0.294 52978.80 150.0000 150.00
0.9H 3.060 0.110 19822.00 150.0000 150.00
1.0H 3.400 0.000 0.00 150.0000 150.00
150 150 150
From the above table it is found that hoop tension is maximum at a level 0.6H from top, 150 150
whereas earlier it was found to be maximum at base of wall 150
Reinf. has been provided considering the critical value among the above . 150 150
Design of section for Bending Moment 150 150
Design B.M. = 150.00 N-m 150
Depth of section reqd.
from no-crack criteria = 21.21 mm
Thickness provided = 400.00 mm
sbt-developed = 0.01 N/mm2 O.K. sbt-Permissible = 2.00 N/sq mm
Clear cover = 45.00 mm
Effective depth = 350.00 mm
Area of steel reqd. = 3.27 mm2
Earlier Area of steel provided as distribution steel = 392.70 mm2
Additional Area of steel required = -389.43 mm2
Spacing of 12 mm dia bars required = -290.41 mm
Hence provide additional 12 mm dia bars at 200 mm c/c for a height of 1.0 m
above base on inner face ( these bars will be additional to the earlier bars)
Design of Middle Ring Beam B3 :
The ring beam connecting cylindrical portion and conical dome.
The load W transmitted through the tank wall, at the top of conical dome consists of
Assuming size of beam B = 1500 mm
D1 = 650 ( Depth at Junction )
D2 = 550 (Depth at Edge)
Dav = 600 mm
1. Load of top Dome =21.77 x 0.66 = 14.38 kN/m
2. Load due to ring beam =( 0.55 - 0.2 ) x (0.55 x 1 x 25) = 4.81 kN/m
3. Load due to tank wall =(3.4 x ( ( 200 + 400)/2)/1000) x25 = 25.50 kN/m
4. Self weight of ring beam =( 1.5 - 0.4 ) x ( 0.6 )x 25 x1 + 3.0 x 1.1 = 19.80 kN/m
(Considering a Live load = 3 kN/m2)
Total vertical load = 64.49 kN/m
Thrust from the Conical Dome
Inclination of conical dome with vertical fo = 45.00
sinf0 = 0.71
cosf0 = 0.71
tanf0 = 1.00
 PW = W x tanf0 = 64.49 kN/m
Pw = w x h x d3 = 21.66 kN/m
Hoop tension in the ring beam.
P3 = (64.49 + 21.66) x 10.6/2 = 456.60 kN/m
This is to be resisted by hoop reinforcement
Area of hoop steel is given as
Ash = (456.6 x 1000) / 150 = 3043.98 mm2
Number of 20 mm dia bars required 9.69
So provide 20 mm dia bars 10 No. placed symmetrically OK
Actual area of hoop steel provided = 3141.59 mm2
Stress in the equivalent section
seq. section =(456597.4 ) / (1500x 600)+(8 x 3141.59) = 0.494 N/mm2
As seq. < 1.5 Provided Section O.K.
The projecting portion of this beam will act as balconey so the moment coming due to load on balconey
Projecting width = = 1500 - 400 = 1100 mm
considering live load of 3 kN / m2 on the projecting portion
Bending Moment = = 3 x 1.1 ^2 / 2 = 1.82 kN m
Total Depth of Beam available = 600 mm
Area of steel required =1815000 / 150 x 0.88 x 555 = 24.92 mm2
As very small amout of steel is required, the shear reinforcement provided in the beam will cater the need.
Shear Reinforcement
Provide 10 mm dia 2 legged stirrups at 300 mm C/c
Area of shear reinforcement provided = 523.60 mm2
Area of steel available to cater for Cantilver Moment = 261.80 mm2
Design of Conical Shell :
Meridional Thrust
Weight of water acting as a load on the conical dome.
Ww ( 3.14 / 4 x (10.6 ^2 - 8.6 ^ 2 ) x3.4 x 9800 ) + ( ( 0.5 x 1 x (10.6 - 8.6 ) / 2 ) x ( 3.14 x
( 10.6 + 8.6 ) x 0.5 ) ) x 9800
Ww = 1152688.0437 N
Let thickness of Conical Dome = 660 mm
Self weight of Conical Dome
Ws =PI x ( 10.6 + 8.6 ) / 2 ) x ( 1 / 0.71 ) x (660 / 1000) x 25000
= 703752.66 N
Load on ring beam B3 W = 64492.45 N/m
Hence vertical load W2 per meter run is given by.
W2 = ( PI x 10.6 x 64492.45 ) + 1152688.04 + 703752.66 ) / ( PI x 8.6)
= 148202.72 N/m
Meridional thrust in the Conical Dome
T0 = ( 148202.72 ) / 0.707 209590.30 N/m
Meridional Stress = 209590.3 / ( 1000 x 660 ) 0.32 N/mm2
OK
Calculation of Hoop Tension in Conical Dome

W
B3 D' = diameter of conical dome at any height h'
above base
p
D'
h0
q h'

B2

D' = 8.6 + 2 x h' x 1

Intensity of water pressure p = (3.4 + 1 - h' ) x 9800

Self weight of conical part q = 0.66 x 1 x 1 x 25 16.50 kN/m

Hoop tension is given by

P0 = (p/cosf0 +q.tanf0) x D'/2

Values of P0 for h' = 0 to h' = hc
h' p p/cosf0 q q*tanf0 D'/2 Hoop Tension
0 43120 60980.89 16500 16500 4.3 333167.822 N
 0.5 38220 54051.24 16500 16500 4.8 338645.963 N
1 33320 47121.60 16500 16500 5.3 337194.458 N
( The table showing stresses for 20 sections throughout the depth is appended )
Maximum hoop tension = 338938.12 N
Design of Walls
Meridional Stress = 0.32 N/mm2
Max Hoop tension = 338938.12
This hoop tension will be resisted by the Hoop steel
Area of hoop Steel As = = 338938.12 / 150 = 2259.59 mm2
Area of steel on each face = 2259.59 / 2 = 1129.79 mm2
Spacing of 25 mm dia bars 434.48 mm (required)
Provide 25 mm dia bars at 120 mm C/c
Steel provided 4090.62 mm2 on each face O.K.
Maximum Tensile Stress in Composite Section
st-compostie sect. = 338938.12 / ( 1000 x 660 + 8 x 8181.23 ) = 0.467
Thus st-compostie sect.
< sdt permissible Provided Thickness is O.K.
In Meridional Direction Provide distribution steel 0.20%
Area of Distribution Steel = 1320 mm2
Area of Steel required on each face = 660
Considering 12 mm dia bars, spacing req. 171.4 mm
So provide 12 mm dia bars at 150 mm C/c
Astprovided = 753.98 mm2 O.K.
Design of Bottom Dome :
Diameter of bottom Ring Do = 8.60 m
Rise of bottom Dome h2 = 1.40 m
Radius of bottom Dome R2 = 7.30 m
Total depth of water above
the edges of dome Ho = 3.4 + 1 = 4.40 m
Trigonometric Ratios
sinf2 = 0.589
cosf2 = 0.808
Weight of water on the dome is given by
Wo = {pi/4 x Do2 x Ho - pi x h22/3 x ( 3 x R2 - h2)} x g
Wo = ( PI / 4 x 73.96 x 4.4) - ( PI x 1.96/3 x (3 x 7.304 - 1.4) ) x 9800
= 2092192.4271 N = 2092.19 kN
Let the Thickness of bottom Dome t2 = 250 mm
Self weight of bottom Dome
Self weight of Bottom dome = 2 x PI() x R2 x h2 x t2 x 25
= 401.53 kN
Total weight WT = 401.53 + 2092.19 = 2493.73 kN
Meridional Thrust T2 = = WT / PI x sinf2
T2 = 156771.62 N/m
Meridional Stress = = 156771.62 / ( 250 x 1000 ) 0.627 N/mm2
Less than permissible so OK
Intensity of Load per unit area p2 =WT / ( 2 x PI x R2 x h2)
=2493.73 / ( 2 x PI x 7.3 x 1.4 ) = 38.82 kN/m
Maximum Hoop Stress at the centre of Dome
= p2 x R2 / 2 x t2 = 566984.3095 N/m2
= 0.567 N/mm2 Less than permissible so OK
Minimum reinforcement required = 0.3 - ( 250 -100 / 450 -100 ) x 0.1)
As per IS 3370 (Part II)-1965 0.26 %
Area of steel As = 650 mm2
Provide 12 mm dia bars at 150 mm c/c
Area of steel provided = 753.98 mm2 O.K.
Design of Bottom Circular Beam :
Inward thrust from conical dome = To x sinf0 = 148202.72 N/m
Outward thrust from bottom dome = T2 x cosf2 = 126720.53 N/m
Net inward thrust = 148202.72 - 126720.53 = 21482.19 N/m
Hoop compression in the Beam = 21482.19 x 8.6 / 2 = 92373.42 N/m
Size of the beam assumed B = 450 mm
D = 700 mm
Hoop stress = 92373.42/ ( 450 x 700 ) 0.29 N/mm2
Vertical load on the beam per meter run = To x cosf0 + T2 x sinf2
 209590.3 x 0.71 + 156771.62x0.59= 240502.50 N/m
Self Weight of Beam = 7875.00 N/m
Total Load on the beam w = 248377.50 N/m
Number of Columns Supporting the Ring Beam = 6 No.
Mean Diameter of ring beam: D = 8.6 m
Mean radius of the ring beam R = 4.3 m
Analysis of ring Beam
2q = 60 o
= 1.047 c

q = 30 o
= 0.524 c

Moment and Torsion Coefficients Moment and Torsion coefficients are

C1 = 0.089 (coeff. for suppt. BM) calculated from equations for curved
circular beam supported on columns from
C2 = 0.045 (coeff. for span BM)
standard text book on Reinforced
C3 = 0.0090 (coeff. for torsion ) Concrete- calculations appended
Fm = 12.73 o
Maximum B.M. at Support Mo = 0.089 x 248377.5 x 4.3^2 x 1.05 = 427563.20 N-m
Maximum B.M. at Centre Mc = 0.045 x 248377.5 x 4.3^2 x 1.05 = 216754.75 N-m
Maximum Torsion T = 0.009 x 248377.5 x 4.3^2 x 1.05 = 43483.30 N-m
Loaction of Max. Torsion = 12.73 o

B.M. at the location of Max Torsion = 0 N-m

Shear at location of max. Torsion = 248377.5 x 4.3 x (0.524-(12.73 x PI /180 )) = 321874.02 N
Maximum Shear at Support = 248377.5 x 4.3 x 0.524 = 559215.66 N
Depth of the Section Required from strength criteria
dreq = = (427563.2 x 1000 / 1.64 x 450)^0.5
= 761.01 mm
Depth of Section required from No-Crack Consideration
Dreq = ( 427563.2 x 6 x 1000 ) / ( 450 x 2 )) ^0.5
= 1688.32 mm
So, keep total depth = 1820 mm O.K.
Nominal Cover = 45 mm
Considering Bar Diameter = 20 mm
Effective Depth = 1765 mm
Width of the beam = 450 mm
Type of Beam
As per IS 456 : 2000 clause 29.1. The beam shall be deemed to be a deep beam when the ratio of effective span to
overall depth, l / D is less than 2.5 for a continuous beam
l/D = ( 3.142 x 8.6 ) / ( 6 / 1.82 ) = 2.47 Beam is Deep Beam
Design of the Section ( Longitudional and Main Reinforcement)
a. Section at the Point of Maximum Torsion
Max. Torsion T = 43483.30 N-m
B.M. at the Location of Max Torsion. M = 0 N-m
Equivalent Moment Me1 = M + Mt
Mt = = 43483.3 x ( 1 + ( 1820 / 450 ) /1.7) 129028.88 N-m
Me1 = 129028.88 N-m
Lever arm of deep beam is given by the relation
( As per IS 456 : 2000 clause 29.2 b , for Continuous Beam )
z = 0.20 ( l + 1.5 D ) when 1 <= l/D <= 2.5
where
l = effective span = MIN ( 3.14 x 8.6 / 6 , ( 1.15 x ( 3.14 x 1.43 - 0.45 ) ) )
= 4.50 m
z = 1.45 m
Ast as per lever arm = j * d consideration
Ast1 = 129028884.525 / ( 150 x 0.88 x 1765 ) = 556.98 mm2
Ast as per lever arm of deep beam
Ast1 = 594.63 mm2 = 129028884.525 / ( 150 x 1446.59 )
No of bars calculated for maximum of two cases
No. of 20 mm dia bars req 1.89 No

b. Section at Maximum hogging B.M. (Support)

M0 = 427563.20 N-m
Mt = 0 N-m
Lever arm from deep beam consideration = 1.45 m
Ast as per lever arm = j * d consideration
Ast = 427563.2 x 1000 / 150x 0.88 x 1765 = 1845.68 mm2
Ast as per lever arm of deep beam
Ast = 427563.2 x 1000 / 150x 1446.59 = 1970.44 mm2
No of bars calculated for maximum of above both steels
No. of 20 mm dia bars req 6.27 No
Provide 20 mm dia bars 14 Nos
Area of Steel Provided = 4398.23 mm2 O.K.
( This steel is again checked in redesign after Contunity Analysis )
c. Section at Maximum Sagging B.M.
Mc = 216754.75 N-m
Mt = 0 N-m
Ast as per lever arm = j * d consideration
Ast = 216754.75 x 1000 / 190x 0.88 x 1765 = 738.69 mm2
 Ast as per lever arm of deep beam
Ast = 216754.75 x 1000 / 190x 1446.59 = 788.62 mm2
No. of 20 mm dia bars req 2.51 No
Provide 20 mm dia bars 7 Nos
Area of Steel Provided = 2199.11 mm2 O.K.
Area of Steel reqd. at support bottom from ductility criteria 2199.12 mm2
Reinforcement Scheme
Reinforcement Scheme at Top
At Top 20 mm dia bars 14 Nos, all through
Placing of top steel : shall be placed in two zones
1). Zone one of depth 0.2 D, adjucent to the tension face
Proportion of tension steel = 0.5 ( l / D -0.5 ) = 0.863
No of bars required in this zone = 12.088 No.
Provide 20 mm dia bars 9 No. all through Revise Steel
2). Zone two of depth 0.3 D, on either side of mid depth = 546 mm on either side from mid depth
No of bars required in this zone = 1.912 nos
Provide 20 mm dia bars 5 Nos within depth 546.00 mm above mid depth
And 20 mm dia bars 5 Nos within depth 546.00 mm below mid depth
Provided steel 20 mm dia bars 19 No.
Reinforcement Scheme at Bottom
At Bottom 20 mm dia bars 7 No. all through
Placing of tensile reinforcement to resist positive bending moment
This steel shall be placed within a zone of depth equal to 0.25 D - 0.05l adjucent to tension face = 0.25 m
Transverse Reinforcement
a. At the Point of Max. Torsional Moment
Shear V = 321874.02 N
Torsion T = 43483.30 N-m
Equivalent Shear Ve = 321874.02 + (1.6 x (43483.3 / 0.45)) = 476481.31 N
Nominal Shear Stress Produced = 0.600 N/mm 2

Maximum Shear Stress tcmax = 2.2 N/mm2

% Steel Provided at The Section = 0.55 %
Premissible shear stress in concrete tc = 0.26 N/mm2 as per IS 456:2000 Table 23
As Nominal Shear Stress is greater than permissible shear stress ,shear reinforcement is necessary
The C/s area of shear reinforcement Asv of the stirrups is given by.
Asv = (T . Sv / b1 .d1 . ssv )+( V.Sv / 2.5 . d1. ssv)
b1 = 350 mm
d1 = 1730 mm
So Asv/ Sv = 0.97 mm
Minimum Transverse Reinforcement is governed by
Asv / Sv >= (tve -tc / ssv) * b
Asv / Sv = 1.02 mm
Using 12 mm dia 4 legged stirrups, Asv = 452.39 mm2
Hence Spacing of Stirrups
Sv = 440 mm C/c
However the spacing of the stirrups should not exceed the least of
1. x1 = 350 +20 + 12 382 mm y1 = = 1730 + 20 + 12 1762 mm
2. x1 + y1 / 4 = ( 382 + 1762 ) / 4 530 mm
3. 300 mm
So provide 12 mm dia 4 legged stirrups at 300 mm C/c
b. At the Point of Maximum Shear
Shear at Support = 559215.66 N
Nominal Shear Stress = 0.70 N/mm2
% Steel at Support = 0.55 %
Permissible shear sterss in concrete = 0.260 N/mm2
Shear to be resisted by Stirrups = 352710.66 N
Spacing of 12 mm dia 4 legged stirrups 339.57 mm C/c
Provide 12 mm dia 4 legged stirrups at 120 mm C/c OK
c. At Mid Span
At mid span provide nominal shear reinforcement given by
Asv/Sv = 0.4.b / 0.87.fy
Asv/Sv = = 0.4 x 450 / 0.87 x415 0.499
Spacing of 12 mm dia 4 legged stirrups at 907 mm
Max. Permissible Spacing = 0.75 x d = 1323.75 or 300 mm whichever is less
So, provide 12 mm dia 4 legged stirrups at 300 mm C/c
Side Face Reinforcement
As beam is deeper than 450 mm and subjected to torsion provide side face reinforcement @ 0.1 % of gross area.
So Area of Side face Reinfor. = 0.1 / 100 x 450 x 1820 819 mm2
So, provide 12 mm dia Bars 12 Nos. So Al = 1357.17 mm2 OK
Design of Columns :
Numbers Columns Supporting the Tank. 'n = 6 Nos.
Mean Circular Diameter of C.L. of Columns D0 = 8.6 m
Staging Height ( upto bottom of ring beam) = 13.18 m
Ht. Below G.L .( upto top of fdn. ring beam) = 0.6 m
Height of panels above G.L = 2.76 m
Height of Bottom Pannel h' = 2.76 m
Diameter of Column = 500 mm OK
Nos of bracing levels = 4
Vertical Load on Columns
1. Weight of water = 2983343.15 N
2. Weight of Tank.
a. Weight of top Dome = 378051.41 N
b. Weight of Cylindrical wall = 849172.49 N
b. Weight of Conical Dome = 703752.6574 N
c. Weight of Bottom Dome = 401534.81 N
d. Weight of Bottom Ring Beam = 553187.34 N
Total Weight of Tank = 2885698.7 N
Total Superimposed Load = 5869041.9
Or Total Load = load on bottom beam per meter x PI x Dia of Ring Beam = 6710587.87 N
Load per Column = 1118431.31 N
Weight of Column per m height = 4908.74 N
Assume size of B = 400 mm
brace D = 600 mm
Length of Each Brace = L = R x( SIN 2p / n)/(COS p/n)
L = =8.6/2 x (SIN 2.PI/6) / (COS PI /6) = 4.30 m
Clear Length of Each Brace = 4.3 - 0.5 = 3.80 m
Weight of Each Brace = 0.4 x 0.6 x 3.8 x 25 = 22.80 kN
Weight due to one flight of stair = 33.88 kN
The Total Weight of Column Above Each Brace
Above Brace No. Description Weight (N)
(from top)
1 = 1118431.31 + 2.76 x 4908.74 + 33875.16 1165834.95
2 =1165834.95 + 2.76 x 4908.74 + 22800 + 33875.16 1236038.59
3 = 1236038.59 + 2.76 x 4908.74 + 22800 + 33875.16 1306242.23
4 = 1306242.23 + 2.76 x 4908.74 + 22800 + 33875.16 1376445.87
5 = 1376445.87 + 2.76 x 4908.74 + 22800 + 33875.16 1446649.51
At fdn. Level =1446649.51 + 2.76 x 4908.74 + 22800 + 33875.16 1516853.14
Wind Load Calculation (Refer IS - 875 Part 3 1987)
Basic Wind Speed (as per Appendix A) Vb = 39 m/s
Design wind speed Vz = k1 x k2 x k3
where k1 (Probability factor) 1.06 (Table 1 of code)
k2 (Terrain factor) 1.1 (Table 2 - for Category 2, Class B)
k3 (Topography factor) 1.0 (Clause 5.3.3 of code)
Vz = 45.474 m/s
Design Wind Pressure = 0.6 x Vz2 = 1240.731 N/m2
Shape Factor = 0.7 ( for circular sections)
Wind Load on Tank ,Domes and Ring Beam
So, wind load on tank , domes and ring beam = 66359.49 N
It may be assumed that this force acts at the Mid-height of Cylindrical Portion of the Tank
So, the point of Application of Wind Pressure = 4.52 m
above bottom of ring beam.
Wind Load on Columns
Wind load on panels = (2.76 x 6 x 0.5) x 1240.73 x 0.7 + 0.6 x 9.1 x 1240.73 = 13955.24 N
Wind load at the level of Ring = 0.5 x 2.76 x 6 x 0.5 x 1240.73 x 0.7 = 3590.43 N
Beam Supporting Tank
The point of Contraflexure O1 , O2 , O3 , etc are assumed to be at mid-height of each pannel.
Shear forces and Moments at these panels due to wind is given by,
Mid Ht. Level Qw Mw
Above G.L. N N-M
11.80 m 69949.92 396335.91
9.05 m 83905.17 608348.22
6.29 m 97860.41 858821.18
3.53 m 111815.65 1147754.79
0.78 m 125770.90 1475149.06
-1.98 m 139726.14 1841003.97
Axial Thrust , Shear Force and Bending in the Columns
Axial Thrust Vmax = 4 x Mw / n x D0 (In the farthest Leeward Column)
Shear Force Smax = 2 x Qw / n
Bending Moment M = Smax x h/2
 Level Vmax Smax M
Above G.L. m N N N-m
11.80 m 30723.71 23316.64 32130.33
9.05 m 47158.78 27968.39 38540.44
6.29 m 66575.29 32620.14 44950.55
3.53 m 88973.24 37271.88 51360.66
0.78 m 114352.64 41923.63 57770.77
-1.98 m 142713.49 46575.38 64180.87
The farthest leeward column will be subjected to the superimposed axial load plus V max.
The column on the bending axis, on the other hand, will be subjected to superimposed axial
load plus a bending moment M
The critical combination for the Panels given as
Panel at Level Farthest Leeward Column Column on bending axis
Above G.L Axial Load Vmax Axial Load B.M.
m N N N N-m
11.80 m 1165834.95 30723.71 1165834.95 32130.33
9.05 m 1236038.59 47158.78 1236038.59 38540.44
6.29 m 1306242.23 66575.29 1306242.23 44950.55
3.53 m 1376445.87 88973.24 1376445.87 51360.66
0.78 m 1446649.51 114352.64 1446649.51 57770.77
-1.98 m 1516853.14 142713.49 1516853.14 64180.87 Design values
Design of Column on bending axis for combined axial load and bending moment
Axial Load = 1516853.14 N
Bending Moment = 64180.87 N-m
Diameter of Column = 500 mm
ssc = 190 N/mm2
scbc = 10 N/mm2
scc = 8 N/mm2
Effective Cover = 45 mm
As wind effect is taken into consideration the permissible stresses may be increased by 25 %
Considering = 1.70 % Steel
Asc required = 3337.94 mm2
Provide 25 mm dia bars 16 No.
Asc provided = 7853.98 mm2 OK
Equivalent area of the Column = PI/4 x 500^2 + (m-1) x 7853.98 = 259181.39 mm2
Equivalent moment of Inertia = PI/64 x d + ( m - 1) Asc .d1 / 8
4 2

d = 500 mm
d1 = 410 mm
MoI = PI/64 x500^4 +(m-1) x 7853.98x (410^2) / 8 = 4.39E+09 mm4
Direct Stress in the Column
scc1 = 1516853.14 / 259181.39 5.85 N/mm2
Bending Stress in the Column
scbc1 = ( 64180873.83 / 4388215888.44 ) x 250 = 3.66 N/mm2
For Safety of Column
scc1 / scc + scbc1 / scbc < = 1
= ( 5.85 / 10 ) + (3.66/ 12.5 ) = 0.88
(Increase in permissible stresses 25 % ) Stresses are Within Safe Limits
Axial Load Carrying Capacity of Column
P = 3000220.9842 N OK
Thus axial load capacity is greater than the maximum axial load on leeward column.
Tie Bars
Considering Diameter of link bars = 10 mm
Spacing of Link Bars
Least of
a. 16 times dia of main bar 400 mm
b. 300 mm 300 mm
Spacing of Ties as per IS 13920 : 1993 (Code for Ductile Detailing of structures)
As per Clause 7.4 of the code special confining reinf. shall be provided at junctions of columns and braces
and also over a length L0 above and below the junctions.
Length L0 shall be the greatest of the following :-
a) larger lateral dimension of the member = 500 mm Thus L0 = 500 mm
b) 1/6 of the clear span of the member = 360.00 mm
c) 450 mm
Considering a spacing of 90mm, area of bar to be used as circular hoops is given by
Ash = 0.09 x S x Dk x fck/fy x [(Ag/Ak) - 1]
where Ash = area of the bar c/s
 S = spacing of hoops
Dk = dia. of the core measured to the outside of hoop reinf. = 440 mm
Ag = gross area of column c/s
Ak = area of the concrete core = p/4 x Dk x Dk
Hence Ash = 75.06 mm2 which is lesser than area of 10 mm dia bar OK
Provide 10 mm dia bar at 90 mm c/c at junctions
Provide 10 mm dia bar at 300 mm c/c for remaining Length
Design of Braces
Maximum moment in the brace is governed by
tan(q + p / n ) = (1 / 2)* cot( q)
q = 29.83 deg.
tan(q + p / n ) = 1.72
(1 / 2)* cot( q) = 0.87
Maximum Bending Moment in the Brace
Brace No Brace Level ht Qw2 Qw1 h1 h2 B.M.
above G.L.
from top (N) (N) (m) (m) (N-m)
1 10.42 m 69949.92 83905.17 2.76 2.76 53093.02
2 7.67 m 83905.17 97860.41 2.76 2.76 62724.50
3 4.91 m 97860.41 111815.65 2.76 2.76 72355.97
4 2.16 m 111815.65 125770.90 2.76 2.76 81987.45
5 -0.60 m 125770.90 139726.14 2.76 2.76 91618.93
Maximum Shear force in the Brace
Shear force in the beam is calculated at the section q = p/n = 3.14 / 6
Brace No Brace Level Qw2 Qw1 h1 h2 S.F.
from top Ht, above G.L. (N) (N) (m) (m) (N)
1 10.42 m 69949.92 83905.17 2.76 2.76 24652.59
2 7.67 m 83905.17 97860.41 2.76 2.76 29124.76
3 4.91 m 97860.41 111815.65 2.76 2.76 33596.93
4 2.16 m 111815.65 125770.90 2.76 2.76 38069.10
5 -0.60 m 125770.90 139726.14 2.76 2.76 42541.27
Maximum Twisting Moment in the Brace
Twisting Moment considered as 5 % of the B.M.
Brace No Brace Level Qw2 Qw1 h1 h2 B.M. at p/n Twisting M.
from top Ht,above G.L. (N) (N) (m) (m) (N-m) (N-m)
1 10.42 m 69949.92 83905.17 2.76 2.76 53093.02 2654.65
2 7.67 m 83905.17 97860.41 2.76 2.76 62724.50 3136.22
3 4.91 m 97860.41 111815.65 2.76 2.76 72355.97 3617.80
4 2.16 m 111815.65 125770.90 2.76 2.76 81987.45 4099.37
5 -0.60 m 125770.90 139726.14 2.76 2.76 91618.93 4580.95
 ANALYSIS DUE TO EFFECT OF CONTINUITY
Membrane Deformations and Stiffness at edges
Top Dome All dimensions are in N & m
Slope at left edge 2*q*R*sin(a) / Et 335666.67/E radians clockwise
Hor. Deflection at edges q*R*R*sin(a)/Et*(1/(1+cos(a)-cos(a)) -241688.44/E m (inward)
Parameter Lambda (3*(R/t)^2)^0.25 9.62
Parameter Kappa 1-cot(a)/(2*Lambda) 0.94
Moment Stiffness R*Et/(4*Lambda^3)*(k+1/k) 0.0007 E N-m / m per radian
Corr. Radial thrust E t/(2*Lambda^2*k*sin(a)) 0.0013 E N/m per radian
Thrust stiffness E t/(Lambda*R*k*sin(a)^2) 0.0047 E N/m
Corr. Moment E t/(2*Lambda^2*k*sin(a)) 0.0013 E N-m / m
Top Ring beam
Thrust stiffness E* b*d/(R*R) 0.0108 E N/m
Moment Stiffness E*b*d^3/(12*R^2) 0.0003 E N-m / m
Cylindrical wall
Parameter Mu (3/(R*R*t*t))^0.25 1.0437
Parameter Z E * t^3/12 0.0023 E
Moment Stiffness 2*Mu*Z 0.0047 E N-m / m
Corr. Thrust 2*Mu^2*Z 0.0049 E N/m
Thrust stiffness 4*Mu^3*Z 0.0102 E N/m
Corr. Moment 2*Mu^2*Z 0.0049 E
Outward disp. of tank wall p*R/E*t 3119862.67 /E m
Clockwise slope of wall p*R/E*t*h 917606.67/E radians
Middle Ring beam
Thrust stiffness E*b*d/R^2 0.0347 E N/m
Moment stiffness E*b*d^3/(12*R^2) 0.0012 E N-m / m
Conical Dome
Hoop tension at top of dome T1 = 337194.46 N
Hoop tension at bottom of dome T2 = 333167.82 N
Outward defl. At top 0.5*D*T1/E*t 2707773.68/E m
Outward defl. At bottom 0.5*dr*T2/E*t 2170638.84/E m
Slope at top tan(a)*(2*T1-T0)/E*t -1159992.45/E radians
Slope at bottom tan(a)*(2*T2-T0)/E*t -1327160.52/E radians
Parameters for Calculating Moment and Thrust Stiffness
Delta (12*cot(a)^2/t^2)^0.25 2.29
l 0.5*D/sin(a) 7.50
l' l - (hc/cos(a)) 6.08
epsilon 2*DELTA*l^0.5 12.54
epsilon' 2*DELTA*l'^0.5 11.30
From Appendix D Table D2 of Jain / Jaikrishna we get the following parameters
K1 138.92
K2=K3 31.64
K4 8.31
K1' 203.71
K2'=K3' 28.73
K4' 8.12
Calculation of moment and thrust stiffness for conical dome
At Top Edge
Moment stiffness E*t*K4*l/((K1K4-K2K3)*tan(a)^2) 0.2678 E
Corr. Thrust E*t*K2/((K1K4-K2K3)*tan(a)*sin(a)) 0.1923 E
Thrust stiffness E*t*K1/((K1K4-K2K3)*l*sin(a)^2) 0.1593 E
Corresponding moment E*t*K3/((K1K4-K2K3)*tan(a)*sin(a)) 0.1923 E
At Bottom Edge
Moment Stiffness E*t*K4'*l'/((K1'K4'-K2'K3')*tan(a)^2) 0.0393 E
Corr. Thrust E*t*K2'/((K1'K4'-K2'K3')*tan(a)*sin(a)) 0.0324 E
Thrust stiffness E*t*K1'/((K1'K4'-K2'K3')*l*sin(a)^2) 0.0534 E
Corr. Moment E*t*K3'/((K1'K4-K2'K3')*tan(a)*sin(a)) 0.0324 E
Bottom Ring Beam
Moment stiffness E*b*d^3/(3*R^2) 0.0028 E
Corr. Thrust E*b*d^2/(2*R^2) 0.0060 E
Thrust stiffness E*b*d/(R^2) 0.0170 E
Corr. Moment E*b*d^2/(2*R^2) 0.0060 E
Bottom Dome
Slope at left edge 2*q*R*sin(a)/E*t-w*R^2*sin(a)/E*t -1049814.29/E

q*R*R*sin(a)/E*t*(1/(1+cos(a)-cos(a))-p*R^2*sin(a)/(2*E*t)+
w*R^3*sin(a)(2*cos(2a)+cos(a)-3)/((6E*t(1+cos(a))
Displ. Of edges -3410290.21/E
Lambda (3*(R/t)^2)^0.25 7.113
Kappa 1-cot(a)/(2*Lambda) 0.903
Moment stiffness R*E*t/(4*Lambda^3)*(k+1/k) 0.0025 E
Corr. Thrust E*t/(2*Lambda^2*k*sin(a)) 0.0046 E
Thrust stiffness E*t/(Lambda*R*k*sin(a)^2) 0.0154 E
Corr. Moment E*t/(2*Lambda^2*k*sin(a)) 0.0046 E
Reactions due to continuity
a) Junction Between Top Dome Top Ring Beam and Wall
Let the net rotation of joint be "s" clockwise and net displacement be "x"
inward. Then the changes in slope and displacement from the membrane state
are as follows -
Component Clockwise slope Inward Displacement
Top dome s - 335666.67/ E x -241688.44 / E
Top ring beam s x
Tank wall s - 917606.67/ E x
Multiplying the above changes of slope and deflections with the corr. stiffnesses, we can get the reactions
imposed by the joint on each member The top dome also imposes an outward horizontal thrust on the joint
equal to 16340.24 N/m
The total reactions from the joint must balance among themselves. Taking clock-wise moment as +ve the
following table gives the reactions from the joint.
Component Clockwise Moment (M) Inward Thrust (H)

Top Dome 0.0007 *s*E - 226.942 + 0.0013 *x*E - 0.0013 *s*E - 437.169 + 0.0047 *x*E -1143.25
314.77

Top Ring Beam 0.0003*s*E 0.0108*x*E

Tank Wall 0.0047 *s*E - 4309.74 - 0.0049 *x*E -0.0049 *s*E + 4498.14 + 0.0102 *x*E
Thrust from dome 16340.24
-
Total 0.0056*s*E -0.0036*x*E -4851.45 = 0 -0.0036*s*E + 0.0257*x*E + 19257.96 = 0
Solving the above
Displacement x = -689700.4 /E
Slope s = 419677.90 /E
Following table gives the final joint reactions for the members meeting there
Net hoop tension
Element Clockwise Moment Inward Thrust
(-x*E*A/0.5*D)
Dome -1156.23 -4296.29 19519.82 N/m
Beam A 113.93 -7427.35 39364.97 N/m
Wall 1042.30 -4616.59 26026.43 N/m
b) Junction Between Middle Ring Beam , Wall and Conical Shell

Let the net rotation of joint be "s" clockwise and net displacement be "x"
inward. Then the changes in slope and displacement from the membrane state
are as follows -
Component Clockwise slope Inward Displacement
Wall s - 917606.67/ E x + 3119862.67 / E
Ring beam s x
Conical shell s+ 1159992.45/ E x + 2707773.68 / E
Reactions at the junction are given by
Component Clockwise Moment (M) Inward Thrust (H)
Wall 0.0047 *s*E - 4309.74 + 0.0049 *x*E + 0.0049 *s*E - 4498.136 + 0.0102 *x*E
15293.66 +31924.44

Middle ring beam 0.0012*s*E 0.0347*x*E

Conical shell 0.2678 *s*E+ 310626.3 - 0.1923 *x*E - -0.1923 *s*E -223105.544 + 0.1593 *x*E
520795.91 +431429.7

Balcony moment
1815.00 -

Water pressure
on beam - 20400.00

Thrust from
64492.45
conical shell -

Total 0.2737*s*E -0.1874*x*E -197370.69 = -0.1874*s*E + 0.2042*x*E + 320642.91 = 0

0
Solving the above equations we get

Displacement x = -2444429.0 /E
Slope s = -952558.69 /E

Following table gives the final joint reactions for the members meeting there

Net hoop tension

Element Clockwise Moment Inward Thrust
(-x*E*A/0.5*D)

Wall -5472.64 -2256.14 184485.21 N/m

Ring beam -1164.10 -84845.79279605 415091.72 N/m
Conical shell 4897.22 2062.23 304400.60 N/m
c) Junction Between Conical Shell, Bottom dome and Bottom ring beam

Let the net rotation of joint be "s" clockwise and net displacement be "x"
inward. Then the changes in slope and displacement from the membrane state
are as follows -

Component Clockwise slope Inward Displacement

Conical shell s + 1327160.52/ E x + 2170638.84 / E

Ring beam s x
Bottom dome s + 1049814.29/ E x -3410290.21 / E

Reactions at the junction are given by

Component Clockwise Moment (M) Inward Thrust (H)

Conical Shell 0.0393 *s*E + 52198.09 + 0.0324 *x*E 0.0324 *s*E + 42956.7 + 0.0534 *x*E +
+ 70257.88 115856.7

Bottom Ring 0.0028*s*E - 0.006*x*E -0.006*s*E + 0.017*x*E

Beam
Bottom dome 0.0025 *s*E + 2676.43 + 0.0046 *x*E - 0.0046 *s*E + 4875.36 + 0.0154 *x*E -
15837.45 52399.22

Net Thrust from -21482.19

-
domes

Total 0.0446*s*E 0.031*x*E + 109294.95 = 0.031*s*E + 0.0858*x*E + 89807.35 = 0

0

Solving the above equations we get

Displacement x = -215398.9 /E
Slope s = -2300842.69 /E
Element Inward Thrust Net hoop compression
Clockwise Moment (-x*E*A/0.5*D)
Conical shell 24990.429500987 72844.36 33061.23 N/m
Ring beam -5117.93553572 10049.61 - N/m
Bottom dome -20027.1837922 -61518.63 12523.19 N/m
Design of OHSR at Basant Vihar Contract Package No. KOT/WS/06

Revised Design incorporating Effects of Continuity

Top Dome
As found out from membrane analysis compressive stresses in the dome are within safe limits.
The continuity effect imposes a hogging moment of = 1156.23 Nm/m at the edges
Also causes a hoop tension of = 19519.82 N/m near edges
Steel needed for hoop tension = 130.13 mm2
Steel provided from Membrane Analysis = 10 mm dia bars at 150 mm C/c
So Astmembrane = 523.60 mm 2
Steel Provided according to Membrane analysis OK
Provide 10 mm dia bars at 150 mm C/C as hoop reinf.
Provide 10 mm dia bars at 150 mm C/C as meridional reinf.

Bending stress at edges = 0.31 N/mm2/m Check this step

Bending stress within Limit provided thickness OK
Hence extend vertical reinf. in wall on outer face ie., 10 mm bars at 180.00 mm C/c
into top dome for a length of 1.50m to take care of the bending moment
Top Ring Beam
The Radial force in the ring beam is reduced from 16340.24 N/m to 7427.35 N/m
So actual reinforcement required Ast= 262.43 mm2
Steel provided from membrane analysis = 3769.91 mm2
Provide 16 mm f bars 12 Nos
Ast = 2412.74 mm2 Provided reinforcement OK
Edge Moment = 113.93 N-m produces sagging moment = 603.82 N-m
Bending stress developed = 0.0218 N/mm2
This stress is too small, and the hoop steel provided will take care of bending moment.
Tank Wall
Hoop tension at top edge = 26026.43 N
Moment at top edge = 1042.30 Nm/m
Hoop tension at bottom edge = 184485.21 N
Moment at bottom edge = -5472.64 Nm/m
Hoop steel needed at top = 173.51 mm2
Hoop steel needed at bottom = 1229.90 mm2
Hoop steel provided according to Membrane analysis
At Top = 1608.50 mm2 O.K.
At Bottom = 4232.88 mm2 O.K.
Hoop stress at bottom = 0.45 N/mm2 Stress within allowable tensile stress of concrete
Area of Steel Required for Bending Moment at bottom edge ( Away from water face)
Ast = 117.45 mm2
However , minimum steel required according to IS 3370 Part II Clause 7.1 = 0.21 %
Astrequired = 642.86 mm2 321.43 sq mm on each face
Steel provided according to Membrane Analysis = 392.70 mm2 O.K.
Middle Ring Beam
Hoop Tension = 415091.72 N
Astrequired = 2767.28 mm2
Area of steel provided as per membrane analysis = 3141.59 mm2 O.K.
Steel provided 20 mm dia bars 10 nos
seq. section 0.45 N/mm2 O.K.
Edge Moment = -1164.10 N-m produces sagging moment = -6169.73 N-m
Bending stress developed = 0.0686 N/mm2
This stress is too small, and the hoop steel provided will take care of bending moment.
Conical Dome
Hoop tension = 304400.6 N
Thrust = 91206.10 N/m
B.M. at top edge = 4897.22 Nm
B.M. at bottom edge = 24990.43 Nm
Area of hoop steel near top = 2029.34 mm2
Hoop steel provided according to Membrane analysis = 8181.23 mm2
consisting 25 mm dia bars at 120 mm C/c
Stresses Developed in the section
st-compostie sect. = 0.42 N/mm2

Rajasthan Urban Infrastructure Development Project. 21 of 40

Design of OHSR at Basant Vihar Contract Package No. KOT/WS/06

Provide 25 mm dia bars at 120 mm c/c on each face Provided Steel OK

Design of Section for Bending at top
Ast required for B.M. at top = 61.27 mm2
Steel provided on outer face at top = 753.98 mm2 as per Membrane Analysis O.K.
Design of Section for Bending at bottom
Depth required for No-crack criteria = 273.81 mm O.K.
Depth of the section povided in membrane analysis = 660 mm
Ast required for B.M. at bottom = 312.65 mm2
Steel provided on inner face at bottom = 753.98 mm2 as per Membrane Analysis O.K.
Additional steel required for B.M. = -441.33 mm2
The additional steel provided
Provide 12 mm bars at 150 mm c/c on inner face so Ast = 753.98 mm2 OK
(this steel is to be provided additionally for a length of 1.50m from junction face)
So the steel available at the junction is 12 mm dia bars at 75 mm C/c
Bottom Dome
Meridonial thrust = 156771.62 N
B.M. = 20027.18 Nm
Since effects of continuity are local so thickness of dome required at bottom junction is checked so that
allowable stress should not exceed the combined bending and direct stresses
Equating allowable stress in bending tension to combined bending and direct stress.
scbt = ( B.M. / Z ) - ( Meridional thrust / c/s area )
scbt = ( 20027183.792 x 6 / ( t^2 x 1000 )) - (156771.622 / 1000 * t )
t= 209.04 mm
However from conservative side ignoring meridional stress = 245.12
So, increase the thickness of bottom dome to 460 mm at edge
This thickness 460 mm at edge shall be gradually reduced to 250 mm over a length of 1.50 m.
Area of Steel required for B.M. on water face = 373.08 mm2
Provide 16 mm f bars 150 mm c/c on water face so Ast provided = 1340.41 mm2
Bottom Ring Beam
Radial inward thrust = 10049.61 N/m
Moment = 5117.94 Nm/m
Moment due to radial force = 9145.14 N-m
So net B.M. = 4027.21 N-m induces hogging moment of -17317 N-m
Hoop Compression = 43213.3149 N
Compressive stresses produced in the section = 0.05 N/mm2 O.K.
Design for Hogging Bending Moment at Support
Net Hogging Moment at support = 410246.21 N-m
Depth of section required for No-Crack Consideration = 1653.78 mm
Hence Provide Total depth = 1820.00 mm
Astrequired = 1770.93 mm2 Provided Reinf. in Membrane analysis is O.K.
Longitudinal reinf. provided in span at bottom and shear reinf. as provided in membrane analysis is OK.

Rajasthan Urban Infrastructure Development Project. 22 of 40

Design of OHSR at Basant Vihar Contract Package No: KOT/WS/06

Design of Braces ( contd..)

Grade of Concrete fck = 30 N/mm2
Grade of steel Fy = 415 N/mm2
Design Stresses And Design Coefficients
scbc = 10 N/mm2
sst = 230 N/mm2
m = 9
mc = 14 (modular ratio for comp.zone = 1.5 m)
k = 0.28 N/mm2
j = 0.91 N/mm2
Q = 1.27 N/mm2
cover = 25.00 mm
The brace will be subjected to critical combination of maximum shear force and twisting moment
when wind blows parallel to it.
The brace will be doubly reinforced due to reversal of moments under wind load
Equating the Moment of Compression area about N.A. to moment of Tensile area about N.A.
Steel Depth Factor e = 0.05 (Eff. Cover / Eff. Depth)
b/2. k2.d2 + (mc -1).Asc (k - e)d = m. Ast (1 - k) d
Substituting Asc and Ast = p.b.d
b/2. k2.d2 + (mc -1).p.b.d (k - e)d = m. p.b.d (1 - k) d
b/2(0.28d)^2 + (14- 1) p.b.d (0.28-0.05)d =9.p.b.d ( 1 -0.28) d
p = 0.0111
As the brace is subjected to Bending Moment and Torsion
Equivalent Moment
Me1 = M + MT
Design of Brace at lowest level:
B.M. = 91618.93 N-m
T. = 4580.95 N-m
Considering Brace Dimensions B = 400 mm
D = 600 mm
MT = T ( (1+D/b) / 1.7) = 4580.95 x ( 1 + 600 / 400) / 1.7
MT = 6736.69 N-m
Me1 = 91618.93 + 6736.69 = 98355.62 N-m
Equating moment of resistance to this moment
b.n. c/2 ( d - n/3) + (mc - 1) . Asc . c' .( d - dc ) = Me1
c = 1.33 x 10 = 13.3 N/mm2
c' = c x( k - e)/ k = 10.94 N/mm2
Asc = 0.0111 x 400 x d
n = kxd = 0.28 x d
677.988 d ^2 + 574.161d ^2 = 98355617.48
dreq = 280.27 mm
Adopt D = 600 mm
Dia of bar to be used = 25 mm
Clear Cover = 25 mm
deff. = 550 mm Available depth greater than req. hence O.K.
Asc = Ast = 2652.84 mm2
Required 25 mm dia bars 5.40 nos.
Provide 25 mm dia bars 6 nos. at top and bottom.
Ast provided in the Section = 2945.24 mm2
% Steel provided in the section = 1.23 %
Design of Shear Reinforcement
Max. Shear = 42541.27 N
Torsion = 4580.95 N
Ve = 42541.27 + 1.6 (4580.95 / 0.4) = 60865.06 N
Nominal Shear Stress = 0.25 N/mm2
tcmax = 2.2 N/mm2 Hence sectional dimensions are O.K
tc = for 1.23% steel 0.446 N/mm2
Provide nominal Shear Reinforement
Area of transverse reinforcement is given as
Asv = (T . Sv / b1 .d1 . ssv )+( V.Sv / 2.5 . d1. ssv)
b1 = 400 - 25 - 50 = 325 mm
d1 = 600 - 25 - 50 = 525 mm

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Design of OHSR at Basant Vihar Contract Package No: KOT/WS/06

Using 10 mm dia 2 legged stirrups, Asv = 157.08 mm2

Avs / Sv = 0.258
Minimum Transverse Reinforcement Req.
Asv / Sv >= (tve -tc / ssv) * b
Asv / Sv = -0.33
Sv req. = 609.65 mm
Spacing should not exceed x1 , (x1 + y1)/4 , 300 mm
x1 = 360 mm
y1 = 560 mm
x1 + y1 / 4 = 230 mm
Spacing of stirrups as per ductile detailing code IS 13920 : 1993 = d/4 = 137.5 mm
Provide 10 mm dia 2 legged stirrups at 130 mm c/c all through
Side Face Reinforcement
As depth is greater than 450 mm and the beam is subjected to torsion
provide side face reinforcement @ 0.1 % of C/s area
Al = 240 mm2
Provide 3 nos. 10 mm dia bars as side face reinf. on each face
As prov. = 471.24 mm2
Provide 300mm x 300mm haunches at the junction of braces with columns and reinforce
it with 10 mm dia bars.

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Design of OHSR at Basant Vihar Contract Package No: KOT/WS/06
DESIGN OF ANNULAR RAFT FOUNDATION

Material
Grade of Reinf. fy 415 N/mm2
Grade of Concrete fck 30 N/mm2
Design Stresses And Design Constants
sst = 230 N/mm2 k = 0.28
scbc = 10 N/mm 2
j = 0.91
m = 9 Q = 1.274
Nominal Cover = 50 mm
S.B.C. of soil = 113.75 kN/m2
Vertical Load from filled Tank and Columns = 9101118.87 N
Weight of Water only = 2983343.15 N
Vertical Load of Empty Tank and Columns = 6117775.71 N
Vmax due to wind load = 856280.917 N
Self Weight of Found n
= 910111.887 N
( Assuming 10 % of the Super Imposed Load)
Total Load on Footing = 10011230.8 N
Area of The Foundation required = 88.011 m2
Radius of column circle = 4.30 m
Let the inner radius of the annular raft be "b" and the outer radius of the raft be "a". The raft shall be so
proportioned that the resultant of the upward pressure lies on the centerline of the column circle.
Assuming that area of raft provided shall be 7.5% more than area reqd.
Area of raft to be provided = 94.61 m2
Equating area of raft inside the column circle to half the area to be provided
Inner radius of annular raft required, "b" = 1.85 m
Equating area of raft outside the column circle to half the area to be provided
Outer radius of annular raft required, "a" = 5.79 m
Provide inner radius of raft "b" = 5.00 m
Provide outer radius of raft "a" = 9.60 m
Foundation width provided = 4.60 m
Inner Diameter of annular raft = 10.00 m
Outer Diameter of annular raft = 19.20 m
Area of Annular Raft provided = 210.99 m2
Moment of Inertia of Slab about Diametrical Axis
M.I. about diametrical axis = 6179.88 m4
Total Load of Empty Tank
(Empty tank + Columns + Self wt of Footing)
Total Load of Empty Tank = 7027887.599 N
Stabilising Moment
Stabilising Moment = 67467720.95 N-m
Factor of Safety againest overturning
F. S = 67467720.95 / 1788187.49 = 37.73 Safe
Base of Raft Below G.L. = 1.6 m
Moment of Wind Forces About Base
Sr. No Wind Force Acting at level Lever Arm Moment
N m N -m
1 66359.49 Tank - 19.30 1280738.2449
2 3590.43 Ring Beam - 14.78 53066.51
3 13955.24 Brace1 level 10.42 12.02 167797.85156
4 13955.24 Brace2 level 7.67 9.27 129337.19962
5 13955.24 Brace3 level 4.91 6.51 90876.547685
6 13955.24 Brace4 level 2.16 3.76 52415.895747
7 13955.24 Brace5 level -0.60 1.00 13955.243809
Total Moment About Base = 1788187.49 N-m
Calculation of Gross Bearing Pressure
A) Super Imposed Load + Wind Load
a. Tank full Condition
smax = 50226.805 N/m2
smin = 44671.1617 N/m2
b. Tank Empty Condition
smax = 36087.025 N/m2
smin = 30531.3818 N/m2

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Design of OHSR at Basant Vihar Contract Package No: KOT/WS/06

Safe Bearing Capacity = 142187.5 N/m 2

( Increased by 25 % for wind load condition)
Hence Stresses are Within Limits
B) Only Super Imposed Load
a. Tank full Condition
sbase = 47448.9833 N/m2

Safe Bearing Capacity = 113750 N/m2 Hence Stresses are Within Limits

Design of Raft

The raft slab shall be designed for a net upward pressure p1+0.5p2 where p1 is the upward pressure
due to dead loads, and p2 is the pressure due to bending effects.
Net upward pressure = 44524.35 N/m2
The design of raft as per IS 11089 is designed and appended
Design of Circular Beam of Raft
The Design of Raft Ring beam is practically similar to the circular ring beam B 2 provided
at the top of column
Design load = 204812.011 N/m
Number of Columns Supporting the Ring Beam = 16 Nos.
Mean Diameter of ring beam: D = 8.6 m
Mean radius of the ring beam R = 4.3 m
Analysis of ring Beam
2q = 22.5 o
= 0.393 radian
q = 11.25 o = 0.196 radian
Moment and Torsion Coefficients
C1 = 0.089 (coeff. for suppt. BM) Moment and Torsion coefficients are taken from
C2 = 0.045 (coeff. for span BM) equations for curved circular beams supported on
C3 = 0.0090 (coeff. for torsion ) columns as given in standard text book on
Reinforced Concrete
Fm = 12.73 o

Maximum B.M. at Support Mo = 0.089 x 204812.01 x 4.3^2 x 0.39 132213.18 N-m

Maximum B.M. at Centre Mc = 0.045 x 204812.01 x 4.3^2 x 0.39 67025.96 N-m
Maximum Torsion T = 0.009 x 204812.01 x 4.3^2 x 0.39 13446.12 N-m
Loaction of Max. Torsion = 4.76 o
B.M. at the location of Max Torsion = 0 N-m
Shear at location of max. Torsion = 204812.01 x 4.3 x (0.2-(4.76 x PI /180 )) 99794.57 N
Maximum Shear at Support = 204812.01 x 4.3 x 0.2 172923.40 N
Depth of the Beam Required
Width of the Beam = 650 mm
Depth reqd. = (132213.18 x 1000 / 1.27 x 650)^0.5
= 399.51 mm
Keep total depth = 1000mm
Nominal Cover = 50
mm
Considering Bar Diameter = 20
mm
Effective Depth = 940mm
Width of the beam = 650mm
Type of Beam
As per IS 456 : 2000 clause 29.1. The beam shall be deemed to be a deep beam when the ratio of effective span
to overall depth, l/D is less than 2.5 for continuous beam.
l = effective span = 4.50
l/D = ( 4.5 / 1 )
= 4.50
Design of the Section ( Longitudional and Main Reinforcement)
a. Section at the Point of Maximum Torsion
Max. Torsion T = 13446.12 N-m
B.M. at the Location of Max Torsion. M = 0 N-m
Equivalent Moment Me1 = M + Mt
Mt = = 13446.12 x ( 1 + ( 1000 / 650 ) /1.7) = 20077.92 N-m
Me1 = 20077.92 N-m
Lever arm of deep beam as per IS 456 : 2000, clause 29.2 b, for continuous beam, is given by the relation
z = 0.20 ( l + 1.5 D ) when 1 < = l/D < = 2.5
z = 1.2006 m
Steel as per lever arm = j * d
Ast1 = 20077915.994 / ( 230 x 0.906 x 940 ) = 102.47 mm2
Steel calculation for lever arm of deep beam

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Design of OHSR at Basant Vihar Contract Package No: KOT/WS/06

Ast1 = 20077915.994 / ( 230 x 1200.59 ) = 72.71 mm2

No. of 20 mm dia bars req 0.33 No
150
b. Section at Maximum hogging B.M. (Support) 150
150
M0 = 132213.18 N-m 150
Mt = 0 N-m 150
150
Steel calculation for lever arm = j * d 150 150
150 150
Ast hogging = 132213.18 x 1000 / 230x 0 150 150 = 674.79 mm2
150 150
Steel calculation for lever arm of deep beam 150 150
150 150
Ast hogging = 132213.18 x 1000 / 230x 150 150 = 478.80 mm2
150.0 150 150
150 150
No. of 20 mm dia bars req 2.15 150
Provide 20 mm dia bars 14 150
Area of Steel Provided = 4398.23 150 O.K.
150
c. Section at Maximum Sagging B.M. 150
150
Mc = 67025.96 N-m
Mt = 0 N-m
Steel calculation for lever arm = j * d
Ast sagging = 67025.96 x 1000 / 230x 0.91 x 940 = 342.09 mm2
Steel calculation for lever arm of deep beam
Ast sagging = 67025.96 x 1000 / 230x 1200.59 = 242.73 mm2
No. of 20 mm dia bars req 1.09 No
Provide 20 mm dia bars 8 Nos
Area of Steel Provided = 2513.27 mm2 O.K.
Reinforcement Scheme
Reinforcemet scheme of steel provided for hogging moment
At Support 20 mm dia bars 14 Nos
Placing of steel provided for negative moment : shall be placed in two zones
a). Zone one of depth 0.2 D , adjucent to tension face
Porportion of tension steel = 0.5 ( ( l / D) - 0.5 ) = 2.00
Number of bars required in this zone = 28.02 Nos
Provide 20 mm dia bars 14 Nos , all through
b). Zone two of depth 0.3 D , on either side of mid depth = 300 mm
Number of bars required in this zone = -14.02 Nos
Provide 20 mm dia bars 0 Nos , all through on either side
Reinforcemet scheme of steel provided for sagging moment
At Mid Span 20 mm dia bars 8 Nos at top.
This steel shall be placed within a zone of depth equal to 0.25 D - 0.05 l adjucent to tension face = 0.02 m
Transverse Reinforcement
a. At the Point of Max. Torsional Moment
Shear V = 99794.57 N
Torsion T = 13446.12 N-m
Equivalent Shear Ve = 99794.57 + (1.6 x (13446.12 / 650) / 1000 ) = 132892.71 N
Nominal Shear Stress Produced = 0.218 N/mm2
Sectional dimensions are OK
Maximum Shear Stress tcmax = 2.2 N/mm 2

% Steel Provided at The Section = 0.72 %

Corrosponding shear stress in concrete tc = 0.322 N/mm2
Provide Nominal Shear Reinforcement
The C/s area of shear reinforcement Asv of the stirrups is given by.
Asv = (T . Sv / b1 .d1 . ssv )+( V.Sv / 2.5 . d1. ssv)
b1 = 530 mm
d1 = 880 mm
Asv / Sv = 0.49 mm
Minimum Transverse Reinforcement is governed by

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Design of OHSR at Basant Vihar Contract Package No: KOT/WS/06

Asv / Sv >= (tve -tc / ssv) * b

Asv / Sv = -0.30 mm
Using 12 mm dia 2 legged stirrups, Asv = 226.19 mm2
Hence Spacing of Stirrups
Sv = 450 mm C/c
However the spacing of the stirrups should not exceed the least of
1 x1 = 530 +20 + 12 562 mm y1 = 880 + 20 + 12 912 mm
2 (x1 + y1) / 4 = ( 562 + 912 ) / 4 369 mm
3 300 mm
So provide 12 mm dia 2 legged stirrups at 300 mm C/c

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Design of OHSR at Basant Vihar Contract Package No: KOT/WS/06
b. At the Point of Maximum Shear
Shear at Support = 172923.40 N
Nominal Shear Stress = 0.283 N/mm2
% Steel at Support = 0.720
Allow. shear stress in conc. = 0.32 N/mm2
Shear to be resisted by Stirrups = -22596.59942
Spacing of 12 mm dia 6 legged stirrups = -6492.56 mm ( reqd.)
Provide 12 mm dia 6 legged stirrups = -6500.00 mm
c. At Mid Span
At mid span provide nominal shear reinforcement given by
Asv/Sv >= 0.4.b / 0.87.fy
Asv/Sv = 0.4 x 650 / 0.87 x 415 0.720
Spacing of 12 mm dia 6 legged stirrups at 942 mm
Max. Permissible Spacing = 0.75 x d = 705
So, provide 12 mm dia 6 legged stirrups at 300 mm C/c
Side Face Reinforcement
As beam is deeper than 450 mm and it is subjected to torsion
provide side face reinforcement @ 0.1 % of gross area.
So Area of Side face Reinf. = (0.1 / 100) x 650 x 1000 650 mm2
So, provide 12 mm dia bars 8 Nos. So Asideface = 904.78 mm2

Rajasthan Urban Infrastructure Development Project 29 of 40

Design of OHSR at Basant Vihar Contract Package No : KOT/WS/06
SEISMIC ANALYSIS OF OHSR

Calculation of net horizontal force due to seismic effects

Design Data
Capacity of Tank = 300 m3
Conc. Grade = 30 N/mm2
Reinf. Grade = 415 N/mm2
Tank Wall Dia. = 10.6 m
Water Col. Ht. = 3m
No. of columns = 6
Dia of column = 500 mm
No. of bracing levels = 4
Seismic Zone = V
Foundation Type = Raft resting on hard rock
Importance factor = 1.5
Soil fdn. Factor = 1
Seismic zone factor = 0.36
Calculation of Lateral stiffness as per IS 1893 : 1984
The staging is assumed to be composed of springs in series connected at the
horizontal brace level.
The stiffness of the springs in one bay = stiffness of all columns
Stiffness of one column in a bay is given by kc = 12EI / L^3
E = 27386.13 N/mm2
I = 0.00307 m4
L = 2.76 m
Hence kc = 48164178.1494 N/m
Hence stiffness of 6 columns acting in parallel
= 288985068.896 N/m (stiffness of one bay)
Since there are 4 bracing levels so No. of bays = 5
Equivalent stiffness of the system K = kc/6 = 9632835.6299 N/m
Calculation of lumped weights
As per IS 1893 equiv. weight acting at the c.g. of the tank = weight of tank + 1/3 weight of staging
Weight of empty tank We = 3727244.72 N
Weight of water in the tank Ww = 2983343.15 N
Weight of staging Ws = 953054.500936 N
Case 1. Tank Empty
Equiv. Weight W = 4044929.55053785 N
Time Period T = 2 x PI x Sqrt.(d/g) where d = W/K is the static defl. at top due to W
= 1.300 secs. g is the acc. due to gravity
Avg. acc. Coeff. (Sa/g) as per IS 1893, Fig. 2 = 0.06 (for 5% damping)
Design hor. Seismic coeff. ah = b x I x F0 x Sa/g = 0.0324
Design Lateral force acting horizontally at the c.g of the tank = 131055.72 N
Case 2. Tank Full
Equiv. Weight W = 7028272.71
Time Period T = 2 x PI x Sqrt.(d/g) where d = W/K is the static defl. at top due to W
= 1.714 secs. g is the acc. due to gravity
Avg. acc. Coeff. (Sa/g) as per IS 1893, Fig. 2 = 0.04 (for 5% damping)
Design hor. Seismic coeff. ah = b x I x F0 x Sa/g = 0.0216
Design Lateral force acting horizontally at the c.g of the tank = 151810.69043 N
Hence the lateral force due to wind calculated earlier 66359.49 N is greater than the maximum lateral
force due to seismic load 151810.690431798 N under tank full condition
Calculation of Hydrodynamic Pressure on tank walls
The tank wall will be subjected to an acc. of alpha - h x g = 0.2119 m/s2
with a natural period of 1.714 secs.
As per IS 1893:1984 convective pressures are very less and hence negligible
Impulsive pressure on wall is given by
Pw = alpha - h x w x h x Sqrt.(3) x cos phi' x [y/h - 0.5 x y2/h2] x tanh Sqrt.(3) x R/h
where w = density of water
h = water column ht.
R = radius of cylindrical wall
y = height measured from top of wall
Pw is maximum when cos phi' = 1 for phi' = 0
Pw = 1122.36 [y/h - 0.5 x y2/h2]
The following table shows the variation of impulsive pressure and consequent hoop force along the ht.
Level y as % of h Pw (N/m2) Hoop force (N/m)
0.2h 202.02 1070.73
0.4h 359.15 1903.52
0.6h 471.39 2498.37
0.8h 538.73 2855.28
1.0h 561.18 2974.25
This hoop force is to be added to the hoop force obtained from membrane analysis under static loading
and the section shall be checked for strength and crack resistance under the combined loads.
Dist. From Top Impulsive hoop Static hoop Total hoop Area of steel Area on Spacing
force force force reqd. each face reqd. of 16
mm dia bars
0.2h 0.68 1070.73 35319.20 36389.93 242.60 121.30 1657.052
0.4h 1.36 1903.52 70638.40 72541.92 483.61 241.81 831.244
0.6h 2.04 2498.37 105957.60 108455.97 723.04 361.52 555.986
0.8h 2.72 2855.28 141276.80 144132.08 960.88 480.44 418.366
1.0h 3.4 2974.25 176596.00 179570.25 1197.13 598.57 335.802
Hence reinforcement scheme as provided earlier is OK

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Design of OHSR at Basant Vihar Contract Package No : KOT/WS/06
Checking the composite section for crack resistance
Maximum hoop tension = 179570.25 N
Tensile stress = 179570.25 / (1000 x 400 + 8 x 4232.88)
= 0.41 N/mm2 OK

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Design of Annular Raft foundation with Ring beam

The annular raft with ring beam shall be designed according to IS : 11089 - 1984

Annular raft slab

Circular Ring Beam

Inner Dia ( 2b )

Outer Dia ( 2a )

Annular Raft Slab

Design Data
Total vertical load from superstructure = 9101118.87 N (excluding s/w of foundation)
Self weight of Foundation = 910111.8867 N
Total vertical load at foundation base level = 10011230.75 N
Safe bearing capacity of soil = 113.75 KN/m2
Total Bending Moment at base due to wind = 1788187.491 N-m
Approx. area of footing required = 88.01 m2
Eccentricity = 0.1786 m
Density of soil = 18 KN/m3
Depth of Foundation below G.L. = 1.6 m
Overburden pressure due to depth of foundn. = 28800 N/m2 (P0)
Net safe bearing capacity of soil = 84950 N/m2 (qall)
Radius of column centerline "c" = 4.3 m
Under dead loads the soil pressure under the raft is uniform over the whole area whereas under
lateral loads the soil pressure is linearly varying.
As per IS : 11089 - 1984 Clause 5.1.2 the raft may be designed for an upward pressure p = p1 + 0.5 p2
where p1 = uniform pressure due to dead loads, and p2 = pressure due to bending effects.
Calculation of footing dimensions
The raft shall be so proportioned that the resultant of the upward pressure lies on the
centerline of the column circle. Let "b" be the inner radius and "a" be the outer radius of the raft.
Assuming that area of raft provided shall be 7.5% more than area reqd.
Area of raft to be provided = 94.61 m2
Equating area of raft inside the column circle to half the area to be provided
Inner radius of annular raft required, "b" = 1.85 m
Equating area of raft outside the column circle to half the area to be provided
Outer radius of annular raft required, "a" = 5.79 m
Provide inner radius of raft "b" = 5.00 m
Provide outer radius of raft "a" = 9.60 m
Width of raft provided = 4.60 m
Diameter of annular portion = 10.00 m
Outer diameter of annular raft = 19.20 m
Moment of Inertia of raft = 6179.88 m4
Area of footing provided = 210.99 m2
Calculation of modified pressure for designing raft
Uniform pressure due to dead loads p1 = 43135.44 N/m2
Linearly varying pressure due to lateral loads p2 = 2777.82 N/m2
Design pressure at base = p1 + 0.5 p2 = 44524.35 N/m2
Concentric Loading = 9394164.273 N

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Radial And Concentric Moments Acting on the Raft Slab
Distance Bending moment in slab due to Net Bending moment Depth
from UDL Concentric Loading UDL - Con
centre Circum Radial Circum Radial Circum Radial dreq dprovided
Mt Mr Mt Mr Mt Mr depth for Max of Mt ,Mr
5.000 899898.33 0 2457113.14 -210428 1557214.81 210427.6442 1105.40 500
5.200 865974.67 33111.51128 2355278.25 -167412 1489303.58 200523.72 1081.03 514.54
5.400 835688.93 60868.17529 2262450.67 -131184 1426761.73 192052.12 1058.08 529.09
5.600 808471.69 83899.54999 2177441.87 -100716 1368970.18 184615.39 1036.43 543.63
5.800 783851.88 102730.4819 2099259.46 -75160 1315407.58 177890.50 1015.96 558.18
6.000 761437.30 117801.498 2027069.16 -53812 1265631.86 171613.50 996.55 572.72
6.200 740899.43 129484.6942 1960165.13 -36083 1219265.70 165567.68 978.12 587.27
6.400 721961.52 138096.2243 1897946.63 -21478.14 1175985.11 159574.36 960.61 600
6.600 704389.24 143906.1982 1839899.55 -9579.432 1135510.31 153485.63 943.93 1100
6.800 687983.18 147146.586 1785581.59 -32.07158 1097598.40 147178.66 928.04 1100
7.000 672572.91 148017.576 1734610.35 7466.441 1062037.44 140551.14 912.88 1100
7.200 658012.09 146692.7239 1686653.74 13175.09 1028641.65 133517.64 898.41 600
7.400 644174.58 143323.1483 1641422 17316.47 997247.43 126006.68 884.60 578.03
7.600 630951.25 138040.9714 1598661.4 20082.61 967710.15 117958.36 871.40 556.07
Reinforcement Required For Radial And Tangential Moments
Distance Ast required for Circumferential Moments Ast required for Radial Moments
From N-m mm2 N-m mm2
Centre Circumferential Moment Area of Steel req Radial Moment Area of Steel req
5.00 1557214.81 14941.79 210427.64424556 2019.10
5.20 1489303.58 13886.35 200523.72 1869.69
5.40 1426761.73 12937.37 192052.12 1741.46
5.60 1368970.18 12081.33 184615.39 1629.25
5.80 1315407.58 11306.03 177890.50 1528.98
6.00 1265631.86 10602.03 171613.50 1437.58
6.20 1219265.70 9960.58 165567.68 1352.58
6.40 1175985.11 9403.18 159574.36 1275.96
6.60 1135510.31 4952.48 153485.63 669.42
6.80 1097598.40 4787.13 147178.66 641.91
7.00 1062037.44 4632.03 140551.14 613.01
7.20 1028641.65 8225.02 133517.64 1067.61
7.40 997247.43 8277.07 126006.68 1045.85
7.60 967710.15 8349.11 117958.36 1017.71
Dia of bar to be ussed in Circumferential Direction = 25 mm
Dia of bar to be used in Radial Direction = 20 mm
Distance Spacing of Reinforcement required Spacing of Reinforcement Required
from Dia of Bar 25 mm Dia of bar 20 mm
Centre In Circumferential direction In radial Direction
m Req Provided Req Provided
5.00 32.84 200 #N/A 150
5.20 35.33 200 167.94 150
5.40 37.92 200 180.31 150
5.60 40.61 200 192.73 150
5.80 43.39 200 205.37 150
6.00 46.28 200 218.42 150
6.20 49.26 200 232.15 150
6.40 52.18 200 246.09 150
6.60 99.07 200 469.06 150
6.80 102.49 200 489.16 150
7.00 105.92 200 512.23 150
7.20 59.65 200 294.12 150
7.40 59.28 200 300.24 150
7.60 58.76 200 0 150
Moments in Raft as per IS 11089 - 1984 Practice for Design and Constructrion of Ring Foundation
Distance Moments
From Tangential Radial
centre Mt( N-m) Mr (N - m)
5.00 1418076.21 -210427.64
5.23 1340457.78 -199172.34
5.46 1269812.32 -189728.42
5.69 1205233.18 -181518.10
5.92 1145974.58 -174085.36
6.15 1091417.53 -167067.81

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 6.38 1041044.01 -160175.76
6.61 994417.13 -153176.39
6.84 951165.83 -145881.75
7.07 910972.84 -138139.52
7.30 873565.20 -129825.83
7.53 838706.72 -120839.73
7.76 806191.95 -111098.75
7.99 775841.20 -100535.46
8.22 747496.65 -89094.69
8.45 721018.98 -76731.31
8.68 696284.74 -63408.44
8.91 673184.10 -49096.03
9.14 651618.94 -33769.67
9.37 631501.33 -17409.61
9.60 612752.19 0.00
Design Constants and Permissible Stresses
sst = 230
k = 0.28
j = 0.91
Q = 1.27
Section Requirements
Bar dia to be used in tangential direction = 25 mm
Bar dia to be used in radial direction = 20 mm
Distance Moments Depth Steel Spacing
from centre Mt Mr dtang drad dprovided Asttang Astradial Tangential
5.00 1418076.21 -210427.64 1054.86 406.35 600.00 11338.94 0E+00 43.27
5.23 1340457.78 -199172.34 1025.58 395.33 612.26 10503.68 1560.69 46.71
5.46 1269812.32 -189728.42 998.19 385.84 624.53 9754.62 1457.48 50.30
5.69 1205233.18 -181518.10 972.48 377.40 636.80 9080.13 1367.54 54.03
5.92 1145974.58 -174085.36 948.27 369.59 649.06 8470.60 1286.77 57.92
6.15 1091417.53 -167067.81 925.42 362.07 661.33 7917.66 1211.99 61.97
6.38 1041044.01 -160175.76 903.81 354.52 673.30 7417.96 1141.33 66.14
6.61 994417.13 -153176.39 883.34 346.69 685.66 6957.99 1071.78 70.51
6.84 951165.83 -145881.75 863.92 338.33 698.13 6536.48 1002.51 75.06
7.07 910972.84 -138139.52 845.47 329.23 1100.00 3973.17 602.49 123.48
7.30 873565.20 -129825.83 827.93 319.17 1100.00 3810.02 566.23 128.77
7.53 838706.72 -120839.73 811.24 307.93 1100.00 3657.98 527.04 134.12
7.76 806191.95 -111098.75 795.36 295.26 698.13 5540.21 763.48 88.56
7.99 775841.20 -100535.46 780.25 280.87 685.66 5428.60 703.45 90.38
8.22 747496.65 -89094.69 765.86 264.41 673.60 5323.92 634.56 92.15
8.45 721018.98 -76731.31 752.17 245.38 661.33 5230.61 556.65 93.80
8.68 696284.74 -63408.44 739.16 223.06 649.06 5146.67 468.69 95.33
8.91 673184.10 -49096.03 726.79 196.28 636.80 5071.72 369.89 96.74
9.14 651618.94 -33769.67 715.06 162.78 624.53 5005.70 259.42 98.01
9.37 631501.33 -17409.61 703.93 116.88 612.26 4948.37 136.42 99.15
9.60 612752.19 0.00 693.41 0.00 600.00 4899.57 0.00 100.14
Provided Section of Raft
Radial steel is composed of two different set of bar diameters
Running near to ring beam alon the pherifery S1 Bar dia 20 mm
Running total length of raft along the pherifery S2 Bar dia 16 mm
Distance Provided Tangential Steel Radial Steel
from centre Total Depth Spacing Ast S1 S2
5.00 600.00 200 2454.36926 150
5.23 612.26 200 2454.36926 150
5.46 624.53 200 2454.36926 150
5.69 636.80 200 2454.36926 150
5.92 649.06 200 2454.36926 150
6.15 661.33 200 2454.36926 150
6.38 673.30 200 2454.36926 150 150
6.61 685.66 200 2454.36926 150 150
6.84 698.13 200 2454.36926 150 150
7.07 1100.00 200 2454.36926 150 150
7.30 1100.00 200 2454.36926 150 150
7.53 1100.00 200 2454.36926 150 150
7.76 698.13 200 2454.36926 150 150
7.99 685.66 150 3272.49235 150 150
8.22 673.60 150 3272.49235 150
8.45 661.33 150 3272.49235 150

34 of 40
8.68 649.06 150 3272.49235 150
8.91 636.80 150 3272.49235 150
9.14 624.53 150 3272.49235 150
9.37 612.26 150 3272.49235 150
9.60 600.00 150 3272.49235 150

35 of 40
ng s/w of foundation)

36 of 40
Spacing
Radial
#DIV/0!
201.19
215.44
229.61
244.02
259.08
275.12
292.97
313.21
521.17
554.55
595.78
411.28
446.37
494.83
564.09
669.95
848.91
1210.41
2301.72
-

37 of 40
Design of Staircase for OHSR
Stair supporting arrangement
The staircase is provided along the periphery of the staging. Landings are provided as slabs cantilevering from the
columns and the staircase waist slab spans between the landings as a continuous one way slab
Design of Flight
Design Data Design after preparation of GA
Maximum span of the staircase = 3.15 m
Average width of landing = 1000 mm
Width of staircase = 750 mm
Rise of steps = 150 mm
Tread of steps = 250 mm
Imposed load considered = 300 kg/m2
Concrete Grade = 30 N/mm2
Reinforcement Grade = 415 N/mm2
sst = 230 N/mm2
scbc = 10 N/mm2
modular ratio , m = 9
Clear cover to reinf. = 20 mm
Design Constants
k = 0.28
j = 0.91 Q = 1.27
Load calculation
Let us assume thickness of stair slab = 150 mm
Selfweight of stair slab = 3.75 kN/m2
Selfweight on horizontal plane = 4.37 kN/m2
Selfweight of steps = 1.875 kN/m2
Load due to railing, etc. = 0.15 kN/m2
Imposed load on stair = 3 kN/m2
Total load intensity = 13.15 kN/m2
Design
Udl. On 1.0 m width of waist slab = 13.15 kN/m
Maximum negative B.M. at support = w x l^2 /10 = 13046.315 N-m
Maximum positive B.M. at span = w x l^2 /12 = 10871.929 N-m
Effective depth reqd. from strength criteria deff. = 101.18 mm
Total depth provided = 150.00 mm
Effective depth provided = 124.00 mm OK
Reinforcement reqd. for negative B.M = 504.77 mm2
Reinforcement reqd. for positive B.M = 420.64 mm2
Provide 10 mm dia bars at 150 mm c/c at top Ast prov. = 523.60 mm2
Provide 10 mm dia bars at 150 mm c/c at bottom Ast prov. = 523.60 mm2
Distribution reinf.
Providing 0.12% as distribution steel As reqd. = 180.00 mm2
Provide 8 mm dia bars at 200 mm c/c Ast prov. = 251.33 mm2
Design of Landing
Load calculation
Reaction from adjacent flights = 41.42 kN/m
Assuming landing slab to be 150 mm thick
Selfweight of landing slab = 3.75 kN/m
Total load intensity = 45.17 kN/m
Design
Cantilever span = 750 mm
Moment at face of column = 12703.183 N-m
Effective depth reqd. from strength criteria = 99.84 mm
Total depth provided = 150 mm
Effective depth provided = 124 mm OK
Ast reqd. at top = 491.49 mm 2

Provide 10 mm dia bars at 150 mm c/c at top Ast prov. = 523.60 mm2
These bars are to be anchored into columns for a length Ld (development length)
Distribution reinf.
Providing 0.12% as distribution steel As reqd. = 180.00 mm2
Provide 8 mm dia bars at 200 mm c/c at top Ast prov. = 251.33 mm2
Check for shear in landing slab
Shear at face of column = 33.88 kN
Shear stress developed = 0.273 N/mm2
40
For the reinf. provided at top, pt = 0.42 %
Corresponding permissible shear stress Tc = 0.284 N/mm2 Hence safe in shear
Axial force on column from landing slab
Force = 33.88 kN

40
 Permissible Shear Stress In Concrete

100 As/bd Grade of Concrete

M20 M25 M30 Interpolator
0.15 0.18 0.19 0.20 % Tc
0.25 0.22 0.23 0.23 0.5 0.31
0.50 0.30 0.31 0.31 0.55 0.322
0.75 0.35 0.36 0.37 0.75 0.37
1.00 0.39 0.40 0.41
1.25 0.42 0.44 0.45
1.50 0.45 0.46 0.48
1.75 0.47 0.49 0.50
2.00 0.49 0.51 0.53
2.25 0.51 0.53 0.55
2.50 0.51 0.55 0.57
2.75 0.51 0.56 0.58
3.00 0.51 0.57 0.60