Reinforced Concrete Tanks 4 Year Civil: Rectangular Tanks By: Abdel Hamid Zaghw

Reinforced Concrete Tanks
4th year Civil
Lecture 1
Rectangular Tanks
By: Abdel Hamid Zaghw
2
Cracking Prof. Abdel Hamid Zaghw
Structure Categories
Structures are divided into 4 categories:
• Category (1) : Tension Side protected
• Category(2) : Tension Side unprotected
• Category(3) : Tension Side subjected to damaging effects
• Category(4) : Tension Side subjected to severe conditions
Water Side sections are Category 3

Air Side sections are Category 2
3
Design of Water Side Sections

Depth Calculation
• Calculate the concrete stress under working loads
• From this step calculate the concrete stress due to Nw
and the concrete stress due to Mw
N 1000 N w 1000 Nw
f ct N w (kN)   w 
1000  t
 N/mm 2
bt t
6M w 106 6M w 106 6M w 103
f ct M w (kN.m)     N/mm 2
bt2 1000  t 2 t2
  f ct ( N ) 
• Calculate tv  t 1   
  f ct ( M ) 
4
• Calculate η from the following table

tv mm η
< 100 (0 - 100) 1
< 200 (100 - 200) 1.3
< 400 (200 - 600) 1.6
> 600 (600 - ) 1.7
• Calculate the concrete cracking stress

f ctr  0.6 f cu N/mm 2
• Check that
f ct   f ct ( N w )  f ct ( M w ) 
f ctr

5
Important Note
• An Air Side Section subjected to small
eccentricity tension shown be treated as a water
side section if concrete stress on the water side
is tensile.
f ct   f ct ( N w )  f ct (M w )  0
N w 6M w 6M w t
f ct   0 Nw  ew 
b t b t 2
t 6
6
Design of Water Side Sections

Reinforcement Calculation
• Calculate the stresses under ultimate loads.
• Calculate βcr from code tables 4-14 or 4-15
• Multiply fy by βcr calculated in step (1) and use
this reduced value in calculating the required As
• The maximum diameter of used steel should not
exceed that given in code tables 4-14 or 4-15.
• The minimum cover is given in the code table
4-13
7
βcr and Bar Diameter

Code Table 4-15
fs N/mm2 Reduction Factor βcr Largest Bar Diameter in mm φmax
WSD Steel 36/52 Steel 40/60 Category 1 Category 2 Category

3&4
220 1.00 .92 18 12 8
200 .93 .83 22 16 10
180 .85 .75 25 20 12
160 .75 .67 32 22 18
140 .65 .58 --- 25 22
120 .56 .5 --- --- 28
8
Type
Minimum cover
Code Table 4-13
Category Slabs and Walls All other

fcu <250 fcu >250 fcu <250 fcu >250
1 20 20 25 20
2 25 20 30 25
3 30 25 35 30
4 40 35 45 40
9
Approximate Depth Estimation

• Assume fcu = 25 N/mm2 f ctr  0.6 f cu  0.6 25  .6  5  3 N/mm 2
• Axial Tension Nw in kN:

  f ( N )    f ( N )  η = 1.7
tv  t 1   ct w   t 1   ct w   
  f ct ( M w )    0 
N w f cr 3 1.7
  t N w  0.6 N w mm
t  1.7 3
• Pure Bending Mw in kN.m:
  f ( N )    0 
tv  t 1   ct w   t 1     t η = 1.6
  ct w    ct w 
f ( M ) f ( M )
6M w 103 f cr 3 1.6 Mw
  t  6M w 103  104 mm
t2  1.6 3 3
10
• Eccentric Tension Mw in kN.m, Nw in kN :
Mw
t 10 4  30 mm
3
• Eccentric Compresion Mw in kN.m, Nw in kN :
Mw
t 10 4  30 mm
3
take t = 400mm 11
Example
Mw =23.3 kN.m Nw = 37.0 kN
Mu =35.0 kN.m Nu = 55.5 kN
Mw 23.3
t 10  30 
4
104  30  309 mm , take t = 400mm
3 3
6  23.3 103
f ct M w    0.874 N/mm 2
4002
f ct N w  
37
 0.0925 N/mm 2
400
  f ct ( N w )   .0925 
tv  t 1     4001     442.3 mm η = 1.6
  f ct ( M w )    0.874 
12
fctr  0.6 fcu  0.6 25  3

f ct   f ct ( N w )  f ct ( M w )  ctr
f

fct  0.0925  0.874 
3
1.6
• Reinforcement Calculations
M 35  1000
e u   630
Nu 55.5
• es = e – t/2 + cover = 630 – 200 + 30 = 460 mm
• Mus = N . es = 25.53 kN.m   0.01
• Assume φmax = 12 mm  cr  0.85
f cu Nu 25 55.5 1000 1.15
As  bd   0.011000  370 
 cr f y fy 0.85  360 0.85  360
 cr
s
= 510 mm2
13
Deep Beams Prof. Abdel Hamid Zaghw
Design of Deep Beams

• Deep Beams have Le/d less than
1.25 for Simply Supported beams
2.50 for Continuous beams
where Le = smaller of (1.05 Lclear and Lcl-cl )
• Design of Deep Beams M
Tu  u
yct
where yct = 0.87 d and not more than:
0.86Le for Simply Supported
0.43Le for Continuous – Mid Span
0.37Le for Continuous – at Support
T
As  u
fy /  s
14
Deep Beam Detailing
Simple Deep Beam

15
Simple Deep Beam Detailing

16
Deep Beam Detailing
Continuous Deep Beam

17
Continuous Deep Beam Detailing

18
Tanks General Prof. Abdel Hamid Zaghw
Type of Tanks
a - According to Position
Elevated
Resting on Soil Under Ground
b- According to Cross-Section
Rectangular Circular
19
Type of Rectangular Tank Walls

One way Two way
h
h
L h
In the vertical direction L

L/h > 2 Shallow Tank
1 < L/h or h/L < 2
Medium Tank
In the Horizontal direction
h/L > 2 Deep Tank L
20
Shallow Tank
Medium Tank
Deep Tank
21
Important Notes:
• The tank classifications: shallow, deep, and medium refer to one
wall of the tank only and not the whole tank.
• A rectangular tank can have walls belonging to different types
present next to each other
Medium
Shallow
22
Shallow Tanks Prof. Abdel Hamid Zaghw
Design of Shallow Tanks

Cantilever Wall
strip 1 m width
23
Cantilever Wall Cont.

24

Hinged Fixed Wall
strip 1 m width
25
Moment Distribution
Carry over = 0.5
Carry over = 0.0
Carry over = 0.0

26
Hinged Fixed Wall Cont.
Fixed End Moments After Moment Distribution

27

28

Fixed Fixed Wall
strip 1 m width
29
Fixed Fixed Wall Cont.

30
BMD – Case 1
NFD
Note :
BMD could be either Case 1 or Case 2
depending on the height to span ratio of the
tank
BMD – Case 2

Reinforced Concrete Tanks 4 Year Civil: Rectangular Tanks By: Abdel Hamid Zaghw

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Reinforced Concrete Tanks 4 Year Civil: Rectangular Tanks By: Abdel Hamid Zaghw

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Reinforced Concrete Tanks

4th year Civil

Water Side sections are Category 3

Design of Water Side Sections

• Calculate η from the following table

• Calculate the concrete cracking stress

Design of Water Side Sections

βcr and Bar Diameter

fs N/mm2 Reduction Factor βcr Largest Bar Diameter in mm φmax

WSD Steel 36/52 Steel 40/60 Category 1 Category 2 Category

Category Slabs and Walls All other

Approximate Depth Estimation

• Axial Tension Nw in kN:

• Eccentric Tension Mw in kN.m, Nw in kN :

• Eccentric Compresion Mw in kN.m, Nw in kN :

fctr  0.6 fcu  0.6 25  3

Design of Deep Beams

Deep Beam Detailing

Simple Deep Beam

Simple Deep Beam Detailing

Deep Beam Detailing

Continuous Deep Beam

Continuous Deep Beam Detailing

Type of Rectangular Tank Walls

In the vertical direction L

Design of Shallow Tanks

Cantilever Wall Cont.

Design of Shallow Tanks

Carry over = 0.5

Carry over = 0.0

Carry over = 0.0

Hinged Fixed Wall Cont.

Fixed End Moments After Moment Distribution

Hinged Fixed Wall Cont.

Design of Shallow Tanks

Fixed Fixed Wall Cont.

Hinged Fixed Wall Cont.

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