# Chapter 13:Water Tanks¶

## Ex13.1:pg-702¶

In [3]:
import math
sigma_cbc=7 #in MPa
sigma_ct=1.2 #in MPa
sigma_st=100 #in MPa
m=13.33 #modular ratio
V=200000 #capacity, in L
V=V/10**3 #in cu m
h=2.5 #assumed depth of water in tank, in m
A=V/h #area of tank, in sq m
B=math.sqrt(4/math.pi*A) #diameter, in m
B=10.1 #assume, in m
H=h+0.5 #including freeboard, in m
w=10 #unit weight of water, in kN/cu m
T=w*H*B/2 #hoop tension, in kN
Ast=T*10**3/sigma_st #in sq mm
s1=10**3*0.785*16**2/Ast #in mm
s1=130 #assume, in mm
t=(T*10**3/sigma_ct-(m-1)*Ast)/1000 #in mm
t=110 #assume, in mm
#hoop tension steel at 1.5 m below top of wall
h=1.5 #in m
T=w*h*B/2 #in kN
Ast=T*10**3/sigma_st #in sq mm
s2=10**3*0.785*16**2/Ast #in mm
s2=260 #assume, in mm
Ads=0.3/100*t*10**3 #vertical steel as distribution steel, in sq mm
s3=235 #in mm
#design of tank floor
D=150 #in mm
Ast=0.3/100*D*1000 #in sq mm
s4=1000*0.785*10**2/Ast #in mm
s4=170 #in mm
print "Summary of design\nDiameter of tank=",B," m\nDepth of tank=",H," m\nTank wall thickness=",t," mm\nSteel-hoop steel; 3 m to 1.5 m below top=16 mm dia @ ",s1," mm c/c\n1.5 m to 0 m below top=16 mm dia @ ",s2," mm c/c\nvertical steel=10 mm dia @ ",s3," mm c/c\nTank floor: Thickness ",D," mm\nSteel=10 mm dia @ ",s4," mm c/c"
#answer in textbook for spacing of 16 mm dia bars from 1.5 m to 0 m below top is incorrect

Summary of design
Diameter of tank= 10.1  m
Depth of tank= 3.0  m
Tank wall thickness= 110  mm
Steel-hoop steel; 3 m to 1.5 m below top=16 mm dia @  130  mm c/c
1.5 m to 0 m below top=16 mm dia @  260  mm c/c
vertical steel=10 mm dia @  235  mm c/c
Tank floor: Thickness  150  mm
Steel=10 mm dia @  170  mm c/c


## Ex13.2:pg-703¶

In [1]:
import math

sigma_cbc=7 #in MPa
sigma_ct=1.2 #in MPa
sigma_st=170 #in MPa
m=13.33 #modular ratio
V=400000 #capacity, in L
V=V/10**3 #in cu m
h=3 #assumed depth of water in tank, in m
A=V/h #area of tank, in sq m
B=math.sqrt(4/math.pi*A) #diameter, in m
B=13 #assume, in m
H=h+0.5 #including freeboard, in m
w=10 #unit weight of water, in kN/cu m
T=w*H*B/2 #hoop tension, in kN
Ast=T*10**3/sigma_st #in sq mm
s1=10**3*0.785*12**2/Ast #in mm
s1=80 #assume, in mm
t=(T*10**3/sigma_ct-(m-1)*Ast)/1000 #in mm
t=175 #assume, in mm
#steel at 2 m below top of wall
h=2 #in m
T=w*h*B/2 #in kN
Ast=T*10**3/sigma_st #in sq mm
s2=10**3*0.785*12**2/Ast #in mm
s2=145 #assume, in mm
Ads=0.3/100*t*10**3 #vertical steel as distribution steel, in sq mm
s3=150 #assume, in mm
#design of tank floor
D=190 #in mm
Ast=0.3/100*D*1000 #in sq mm
s4=1000*0.785*10**2/Ast #in mm
s4=135 #assume, in mm
print "Summary of design\nDiameter of tank=",B," m\nDepth of tank=",H," m\nTank wall thickness=",t," mm\nSteel-hoop steel; 4 m to 2 m below top=12 mm dia @ ",s1," mm c/c\n2 m to 0 m below top=12 mm dia @ ",s2," mm c/c\nvertical steel=10 mm dia @ ",s3," mm c/c\nTank floor: Thickness ",D," mm\nSteel=10 mm dia @ ",s4," mm c/c both ways"

Summary of design
Diameter of tank= 13  m
Depth of tank= 3.5  m
Tank wall thickness= 175  mm
Steel-hoop steel; 4 m to 2 m below top=12 mm dia @  80  mm c/c
2 m to 0 m below top=12 mm dia @  145  mm c/c
vertical steel=10 mm dia @  150  mm c/c
Tank floor: Thickness  190  mm
Steel=10 mm dia @  135  mm c/c both ways