Adopt M$_{20}$ concrete and Fe$_{415}$ steel. The height of tank in limited to 3 m. draw the reinforcement details. Use tables for IS coefficients.

$V=400 KL=\cfrac{ (400×10^{3})}{10}^{3} =400 m^{3}$ $H_{t}$=3 m (Excluding free board assumed) $M_{20}, M_{415}$ $V=\cfrac{(πD^{2})}{4}×H=400= \cfrac{(πD^{2})}{4}×3$ D=13 Assume; $t_{1}$ = 150 mm $t_{2}$=30 H+50=30×3+50=140 mm Whichever greater should be used as thickness $\cfrac{H^{2}}{Dt}=\cfrac{3^{2}}{(13×150)}=4.61

Form IS code: 3370: 1967 :- page no.-35 table no 9

T= Coefficient × WHR

T= Hoop tension

Evaluate the coefficient for the particular value of $\cfrac{H^{2}}{Dt}$ = 4.61

Hoop tension (T)=0.458 ×9810×3×13/2=87613.11 N/mm.

Astr= $\cfrac{T}{σ_{st}} =\cfrac{87613.11}{150}=585 mm^{2}$

Since for hoop tension, the reinforcement is done inner as well as outer side of reinforcement.

∴Astr=585/2=292.5 $mm^{2}$

Now for calculation of Astmin , evaluate the min % reinforcement with help of t=150 mm. Using the relation

Ast min= 0.285/100×1000×150 =427.5〖mm〗^2<585 〖mm〗^2 Astr(total) Assume 10 mm ∅ base. Spacing= (1000×78.5)/292.5=268.37 mm≈250mm Astp=(1000×78.5)/250=314 〖mm〗^2 Total Astp=314×2=628〖mm〗^2

Check

$σ_{ct}=\cfrac{T}{((1000 t)+(m-1)Astp)}$

$m=\cfrac{280}{(3σ_{cbc} )}=\cfrac{280}{(3×7)}=13.33$

$σ_{ct}=\cfrac{87613.11}{((1000×150)+(13.33-1)×628)}$

$σ_{ct}=\cfrac{87613.11}{((1000×150)+12.33×628)}=0.55 N|mm^{2}\lt1.2 N| mm^{2}$

∴ Safe

Vertical Steel:

Form IS code : 3370:1967, page 36 table 10

B.M. = Coefficient × wH$^{3}$

Both are less than Astmin i.e. 427.5 mm$^{2}$

∴Provide Ast=427.5 mm$^{2}$

Assume 10 mm ∅ steel

∴Spacing=(1000×78.5)/427.5=183.62≈175 mm c/c

For Shear :

From IS code 3370: 1967 page 37.

V=Coefficient × WH$^{2}$ (triangular) = 0.222×9810×33 =19.6 KN.(V$_{UD}$)

Ast=$\cfrac{(1000×78.5)}{175}=448.57mm^{2}$

Ast= $\cfrac{100Astp}{(1000×120)}=\cfrac{(1000×448.57)}{(1000×120)}$=0.37%

From page 84 of IS 456: 2000 by interpolation

Zuc= ?

$V_{us}= KZ_{uc}bd$ = (for k value page 72)=$1.3×0.27×1000×120=42.12 KN\gtV_{UD}$

∴Safe

Base reinforcement details :-

Ast min =427.5 mm$^{2}$

Provide 8 mm ∅

Spacing=$\cfrac{(1000×50)}{427.5}$=116.95mm≈100 mm

Reinforcement details:

Type 6: Rectangular water tank