Tank Foundation & Ring Beam Design
Content
Design of foundation for tank 1301B08, 1301B11, 1303B02, 1803B12
Design Data
1 Dia of tank
2 Height of tank
d
H
=
=
3.6 m
3.2 m
3 Cone height
H1
=
0.5 m
44 m/s
1
Calculation of wind velocity as per IS 875 (P3-1987)
4 Basic wind speed
5 Risk Coefficient
Vb
k1
=
=
6 Terrain, ht, stru. Size Coefficient
as per Class B, terrain category 2
k2
=
7 Topography Factor
Design Wind Speed
k3
Vz
=
=
=
8 Designwind pr
9 Inward drag associated with open tank
as per cl. 3.9.7.1(a)- API 650
10 Total external Pressure
P
0.98
1
43.12 m/s
156 km/hr
1115.601 N/m2
=
240 N/m2
=
1355.601 N/m2
As per cl. 3.9.7.1(a)- API 650 formula for for max. ht. of unstiffened shell is based on total
external pressure of 1720 N/m2 which is result of wind velocity of 160km/hr.
Equivalent wind velocity corresponding to wind pr. Of
1355.601 N/m2
is calculated by
11
V
As a conservative consideration design wind vel.
=
=
142.0436 km/hr
156 km/hr
=
83.33716 Kg/m2
13 Projected area of shell = D*H
=
11.52 m2
14 Wind load on shell
=
960.044 Kg
=
1536.07 Kgm
=
69.77064 Kg/m2
12 wind load on cylindrical shell/m2
of projected area
15 Wind moment due to shell
MWs
16 wind load on cone roof/m2
of projected area
17 Projected area of cone roof
=
0.9 m2
18 wind load on cone roof
=
62.79358 Kg
19 C.G. of cone roof from bottom
=
3.366667 m
20 Wind moment due to cone roof
MWr
21 Total overturning moment due to wind M
=
=
211.405 Kgm
1.748 Tm
Calculation of seismic force as per IS 1893 (1984)
22
b
I
=
1
23
=
1.5
24
ao
=
0.04 for Zone III
25 Horizontal Coefficient
ah
=
0.06
=
=
4.5 T
37.5 T
=
0.27 T
b) when tank is full
29 Overturning moment due to earthquake
=
2.25 T
a)
when tank is empty
=
0.432 Tm
b)
when tank is full
=
3.60 Tm
26 Empty wt. of tank
27 Total operating wt.
28 Seismic Lateral force
a) when tank is empty
Design Data for Ring Beam
1 Grade of concrete
2 Grade of steel
=
=
M25
Fe500
3 Dia of tank
d
=
3.6 m
4 Coefficient of soil pressure at rest
u
=
0.4
5 Density of liquid store
=
10 kN/m3
6 Density of earth considered
=
18 kN/m3
=
=
30 degree
0.33
9 Net safe bearing capacity of soil
10 Self weight of tank
11 Self weight of liquid store
=
=
=
50 kN/m2
45 kN
330 kN
12 Inner dia of ring wall
13 Outer dia of ring wall
=
=
3.3 m
3.9 m
15 Dia of foundation
16 Horizontal Shear at top of ring beam
=
5.7 m
7 Angle of repose
8 Coefficient of active earth pressure
a)
b)
Due to wind force
Due to earthquake force
Ka
=
=
10.228 kN
22.5 kN
17 Overturning Moment at top of ring beam
a) Due to wind
=
17.48 kNm
b)
=
36.00 kNm
Due to earthquake
DF=
300mm
1550mm
DP=
3300mm
965mm
300mm
450
900mm
5700mm
Design of ring wall
loading Data
Seismic moment when tank empty
No. of basic loading cases
Loads At tank bottom
Load case
Description of load
1 Empty Wt. of tank
2 Operating Wt. of tank
=
=
vertical Load KN
4.32 kNm
4
Horizontal load KN Moment KN.m
45
375
0
0
0
0
3 Seismic Load when
tank full
0
22.5
36
4 Seismic Load when
tank empty
0
2.7
4.32
Load combination for stability check
Load combination for design
101
=
Load case 2
102
103
=
=
Load case 1+4
Load case 2+3
201
202
=
=
(Load case 2)*1.5
(Load case 1)*0.9+(4)*1.5
203
=
(Load case 2)*0.9+(3)*1.6
Combation of loads for stability check:
Loads At top of Ring Beam
Load case
vertical Load KN
101
375
102
103
Horizontal load KN
0
45
375
Moment KN.m
0
2.7
22.5
4.32
36
Weight of ring wall
Wrb
=
213.33 kN
Weight of sand mat
Ws
=
387.1937 kN
Loads At botton of Ring Beam
Load case
vertical Load KN
101
975.52
Horizontal load KN
0
102
103
645.52
975.52
2.7
22.5
Overturning Moment KN.m
0
11.1105
92.5875
Calculation of Resisting Moment at bottom of Ring Beam
Loads At botton of Ring Beam
Load case
vertical Load KN
101
975.52
102
103
645.52
975.52
Resisting Moment KN.m
977.32353
647.32353
977.32353
Check for Stability
Check for Overturning
Overturning Safety Factor
=
Resisting Moment
overturning Moment
Load case
Overturning safety factor
101 #DIV/0!
102
58.26
103
10.56
Check for sliding
Sliding Safety Factor
Check
>1.5 hence safe
>1.5 hence safe
>1.5 hence safe
=
u*Vertical Load
Horizontal load
Load case
sliding safety factor
101 #DIV/0!
102
103
Check
>1.5 hence safe
95.63
17.34
>1.5 hence safe
>1.5 hence safe
Check for crushing strength of concrete
Pmax/Pmin
=
P
A
+
where A= Area of Ring beam
=
3.39292 m2
where Z= section modulus of Ring beam
=
2.295522 m3
M
Z
Pmax shouldnot be greater than crushing strengh of Concrete = 25 N/mm2
Pmin shouldnot be less than 0
Load case
Pmax (N/mm2)
Check
Pmin (N/mm2)
Check
101
102
0.29
0.20
<25N/mm2 hence safe
<25N/mm2 hence safe
0.29
0.19
>0 hence safe
>0 hence safe
103
0.33
<25N/mm2 hence safe
0.25
>0 hence safe
Calculation of Reinforcement of Ring beam
Ring beam should be design for case for which factored load at top of ring beam is maximum.
Loads At top of Ring Beam
Load case
vertical Load KN
201
562.5
202
203
40.5
337.5
Pu
Pu
Tu
qu1
qu2
Hoop tension on ring beam due to vertical load qu1
=
21.92217 kN/m2
Hoop tension at ring beam botton due to sand qu2
Avg Hoop tension on ring beam /m
=
22.635 kN/m2
Pu=(qu1+(qu1+qu2))*Dp+Df/2
Pu
=
83.59777 kN/m
Direct tension on ring beam /m
Tu
=
137.9363 kN
Ast req. for ring beam = Tu/0.87*fy
Ast
=
ptmin
=
0.2 %
Astmin
=
1509 mm2
use
cover
d1
spacing of bar
Provide
12 mm
dia. @ 150 mm
317.095 mm2
12 dia. Bar
40 mm
=
=
=
2423 mm
181.6003 mm
C/C as a main reinforcement
Calculation of shear reinforcement
use
spacing
Provide 2 legged
8 mm
dia. @ 200 mm
8 dia. Bar
=
364.4247 mm
C/C as a shear reinforcement
Load calculations for Base Slab
Total load coming on the top of foundation
Weight of ring wall
=
=
375 kN
213.33 kN
Weight of soil
Self weight of foundation
=
=
387.19 kN
287.07 kN
Total weight of foundation
=
1262.60 kN
A
Total weight coming on the foundation P
=
1262.60 kN
B
Moment at base of ring beam
M
=
102.7125 kNm
c
Gross pressure at base
G
=
50
=
P
A
=
1262.60
25.51759
=
49.48
kN/m2
Checking of base pressure
A
Check for max. Gross Pressure
Maximum pressure coming
kN/m2 <Gross pr. of soil
so safe
Calculation of Ast at top
Base slab is designed for max. pressure of 50KN/m2 for simlicity
Maximum Factored B.M. at face of ring beam
=
30.375 kNm
Depth required
d
Depth provided
Area of steel required
Ast
Provide
16 mm dia bar @ spacing
Provide
16 mm dia
=
93.83 mm
=
394 mm
=
788.00 mm2
=
255.1547 mm C/C
O.K.
@200 mm C/C
Calculation of Ast at bottom
Pr. From bottom
Pr. From top due to tank wt. & internal soil wt.
Balance pr.
=
=
=
Maximum Factored B.M. at centre of raft
=
Area of steel required
Ast
Provide
16 mm dia bar @ spacing
Provide
16 mm dia
49.48 kN/m2
100.36 kN/m2
50.88 kN/m2
103.9006 kNm
=
788.00 mm2
=
255.1547 mm C/C
@200 mm C/C
Check for punching shear
Perimeter
=
13.49 m
Area of resisting shear
=
25.13931 m2
Shear force
=
3784.635 KN
Tv
=
0.712059 N/mm2
Bc
Ks
=
=
1
1
Tc
=
1.25 N/mm2
O.K.
pt
M15
Concrete Grade
M25
M30
M20
M35
M40 & above
0.15
0.25
0.5
0.75
1
1.25
1.5
1.75
2
2.25
2.5
0.28
0.35
0.46
0.54
0.6
0.64
0.68
0.71
0.71
0.71
0.71
0.28
0.36
0.48
0.56
0.62
0.67
0.72
0.75
0.79
0.81
0.82
0.29
0.36
0.49
0.57
0.64
0.7
0.74
0.78
0.82
0.85
0.88
0.29
0.37
0.5
0.59
0.66
0.71
0.76
0.8
0.84
0.88
0.91
0.29
0.37
0.5
0.59
0.67
0.73
0.78
0.82
0.86
0.9
0.93
0.3
0.38
0.51
0.6
0.68
0.74
0.79
0.84
0.88
0.92
0.95
2.75
3
0.71
0.71
0.82
0.82
0.9
0.92
0.94
0.96
0.96
0.99
0.98
1.01
0.15
0.25
0.29
0.36
0.1
0.07
#VALUE!
Design Data
1 Dia of tank
2 Height of tank
d
H
=
=
3.6 m
3.2 m
3 Cone height
H1
=
0.5 m
44 m/s
1
Calculation of wind velocity as per IS 875 (P3-1987)
4 Basic wind speed
5 Risk Coefficient
Vb
k1
=
=
6 Terrain, ht, stru. Size Coefficient
as per Class B, terrain category 2
k2
=
7 Topography Factor
Design Wind Speed
k3
Vz
=
=
=
8 Designwind pr
9 Inward drag associated with open tank
as per cl. 3.9.7.1(a)- API 650
10 Total external Pressure
P
0.98
1
43.12 m/s
156 km/hr
1115.601 N/m2
=
240 N/m2
=
1355.601 N/m2
As per cl. 3.9.7.1(a)- API 650 formula for for max. ht. of unstiffened shell is based on total
external pressure of 1720 N/m2 which is result of wind velocity of 160km/hr.
Equivalent wind velocity corresponding to wind pr. Of
1355.601 N/m2
is calculated by
11
V
As a conservative consideration design wind vel.
=
=
142.0436 km/hr
156 km/hr
=
83.33716 Kg/m2
13 Projected area of shell = D*H
=
11.52 m2
14 Wind load on shell
=
960.044 Kg
=
1536.07 Kgm
=
69.77064 Kg/m2
12 wind load on cylindrical shell/m2
of projected area
15 Wind moment due to shell
MWs
16 wind load on cone roof/m2
of projected area
17 Projected area of cone roof
=
0.9 m2
18 wind load on cone roof
=
62.79358 Kg
19 C.G. of cone roof from bottom
=
3.366667 m
20 Wind moment due to cone roof
MWr
21 Total overturning moment due to wind M
=
=
211.405 Kgm
1.748 Tm
Calculation of seismic force as per IS 1893 (1984)
22
b
I
=
1
23
=
1.5
24
ao
=
0.04 for Zone III
25 Horizontal Coefficient
ah
=
0.06
=
=
4.5 T
37.5 T
=
0.27 T
b) when tank is full
29 Overturning moment due to earthquake
=
2.25 T
a)
when tank is empty
=
0.432 Tm
b)
when tank is full
=
3.60 Tm
26 Empty wt. of tank
27 Total operating wt.
28 Seismic Lateral force
a) when tank is empty
Design Data for Ring Beam
1 Grade of concrete
2 Grade of steel
=
=
M25
Fe500
3 Dia of tank
d
=
3.6 m
4 Coefficient of soil pressure at rest
u
=
0.4
5 Density of liquid store
=
10 kN/m3
6 Density of earth considered
=
18 kN/m3
=
=
30 degree
0.33
9 Net safe bearing capacity of soil
10 Self weight of tank
11 Self weight of liquid store
=
=
=
50 kN/m2
45 kN
330 kN
12 Inner dia of ring wall
13 Outer dia of ring wall
=
=
3.3 m
3.9 m
15 Dia of foundation
16 Horizontal Shear at top of ring beam
=
5.7 m
7 Angle of repose
8 Coefficient of active earth pressure
a)
b)
Due to wind force
Due to earthquake force
Ka
=
=
10.228 kN
22.5 kN
17 Overturning Moment at top of ring beam
a) Due to wind
=
17.48 kNm
b)
=
36.00 kNm
Due to earthquake
DF=
300mm
1550mm
DP=
3300mm
965mm
300mm
450
900mm
5700mm
Design of ring wall
loading Data
Seismic moment when tank empty
No. of basic loading cases
Loads At tank bottom
Load case
Description of load
1 Empty Wt. of tank
2 Operating Wt. of tank
=
=
vertical Load KN
4.32 kNm
4
Horizontal load KN Moment KN.m
45
375
0
0
0
0
3 Seismic Load when
tank full
0
22.5
36
4 Seismic Load when
tank empty
0
2.7
4.32
Load combination for stability check
Load combination for design
101
=
Load case 2
102
103
=
=
Load case 1+4
Load case 2+3
201
202
=
=
(Load case 2)*1.5
(Load case 1)*0.9+(4)*1.5
203
=
(Load case 2)*0.9+(3)*1.6
Combation of loads for stability check:
Loads At top of Ring Beam
Load case
vertical Load KN
101
375
102
103
Horizontal load KN
0
45
375
Moment KN.m
0
2.7
22.5
4.32
36
Weight of ring wall
Wrb
=
213.33 kN
Weight of sand mat
Ws
=
387.1937 kN
Loads At botton of Ring Beam
Load case
vertical Load KN
101
975.52
Horizontal load KN
0
102
103
645.52
975.52
2.7
22.5
Overturning Moment KN.m
0
11.1105
92.5875
Calculation of Resisting Moment at bottom of Ring Beam
Loads At botton of Ring Beam
Load case
vertical Load KN
101
975.52
102
103
645.52
975.52
Resisting Moment KN.m
977.32353
647.32353
977.32353
Check for Stability
Check for Overturning
Overturning Safety Factor
=
Resisting Moment
overturning Moment
Load case
Overturning safety factor
101 #DIV/0!
102
58.26
103
10.56
Check for sliding
Sliding Safety Factor
Check
>1.5 hence safe
>1.5 hence safe
>1.5 hence safe
=
u*Vertical Load
Horizontal load
Load case
sliding safety factor
101 #DIV/0!
102
103
Check
>1.5 hence safe
95.63
17.34
>1.5 hence safe
>1.5 hence safe
Check for crushing strength of concrete
Pmax/Pmin
=
P
A
+
where A= Area of Ring beam
=
3.39292 m2
where Z= section modulus of Ring beam
=
2.295522 m3
M
Z
Pmax shouldnot be greater than crushing strengh of Concrete = 25 N/mm2
Pmin shouldnot be less than 0
Load case
Pmax (N/mm2)
Check
Pmin (N/mm2)
Check
101
102
0.29
0.20
<25N/mm2 hence safe
<25N/mm2 hence safe
0.29
0.19
>0 hence safe
>0 hence safe
103
0.33
<25N/mm2 hence safe
0.25
>0 hence safe
Calculation of Reinforcement of Ring beam
Ring beam should be design for case for which factored load at top of ring beam is maximum.
Loads At top of Ring Beam
Load case
vertical Load KN
201
562.5
202
203
40.5
337.5
Pu
Pu
Tu
qu1
qu2
Hoop tension on ring beam due to vertical load qu1
=
21.92217 kN/m2
Hoop tension at ring beam botton due to sand qu2
Avg Hoop tension on ring beam /m
=
22.635 kN/m2
Pu=(qu1+(qu1+qu2))*Dp+Df/2
Pu
=
83.59777 kN/m
Direct tension on ring beam /m
Tu
=
137.9363 kN
Ast req. for ring beam = Tu/0.87*fy
Ast
=
ptmin
=
0.2 %
Astmin
=
1509 mm2
use
cover
d1
spacing of bar
Provide
12 mm
dia. @ 150 mm
317.095 mm2
12 dia. Bar
40 mm
=
=
=
2423 mm
181.6003 mm
C/C as a main reinforcement
Calculation of shear reinforcement
use
spacing
Provide 2 legged
8 mm
dia. @ 200 mm
8 dia. Bar
=
364.4247 mm
C/C as a shear reinforcement
Load calculations for Base Slab
Total load coming on the top of foundation
Weight of ring wall
=
=
375 kN
213.33 kN
Weight of soil
Self weight of foundation
=
=
387.19 kN
287.07 kN
Total weight of foundation
=
1262.60 kN
A
Total weight coming on the foundation P
=
1262.60 kN
B
Moment at base of ring beam
M
=
102.7125 kNm
c
Gross pressure at base
G
=
50
=
P
A
=
1262.60
25.51759
=
49.48
kN/m2
Checking of base pressure
A
Check for max. Gross Pressure
Maximum pressure coming
kN/m2 <Gross pr. of soil
so safe
Calculation of Ast at top
Base slab is designed for max. pressure of 50KN/m2 for simlicity
Maximum Factored B.M. at face of ring beam
=
30.375 kNm
Depth required
d
Depth provided
Area of steel required
Ast
Provide
16 mm dia bar @ spacing
Provide
16 mm dia
=
93.83 mm
=
394 mm
=
788.00 mm2
=
255.1547 mm C/C
O.K.
@200 mm C/C
Calculation of Ast at bottom
Pr. From bottom
Pr. From top due to tank wt. & internal soil wt.
Balance pr.
=
=
=
Maximum Factored B.M. at centre of raft
=
Area of steel required
Ast
Provide
16 mm dia bar @ spacing
Provide
16 mm dia
49.48 kN/m2
100.36 kN/m2
50.88 kN/m2
103.9006 kNm
=
788.00 mm2
=
255.1547 mm C/C
@200 mm C/C
Check for punching shear
Perimeter
=
13.49 m
Area of resisting shear
=
25.13931 m2
Shear force
=
3784.635 KN
Tv
=
0.712059 N/mm2
Bc
Ks
=
=
1
1
Tc
=
1.25 N/mm2
O.K.
pt
M15
Concrete Grade
M25
M30
M20
M35
M40 & above
0.15
0.25
0.5
0.75
1
1.25
1.5
1.75
2
2.25
2.5
0.28
0.35
0.46
0.54
0.6
0.64
0.68
0.71
0.71
0.71
0.71
0.28
0.36
0.48
0.56
0.62
0.67
0.72
0.75
0.79
0.81
0.82
0.29
0.36
0.49
0.57
0.64
0.7
0.74
0.78
0.82
0.85
0.88
0.29
0.37
0.5
0.59
0.66
0.71
0.76
0.8
0.84
0.88
0.91
0.29
0.37
0.5
0.59
0.67
0.73
0.78
0.82
0.86
0.9
0.93
0.3
0.38
0.51
0.6
0.68
0.74
0.79
0.84
0.88
0.92
0.95
2.75
3
0.71
0.71
0.82
0.82
0.9
0.92
0.94
0.96
0.96
0.99
0.98
1.01
0.15
0.25
0.29
0.36
0.1
0.07
#VALUE!
