SUPER CHIMNEY
SUPER CHIMNEY

 


How to build the Super Chimney?

Author of the Design is Brajesh Chandra, M.S., ME retired Chief Engineer from KANPUR , India

The concept design was done using ETABS structural design software . The purpose was to see whether it is possible to build the chimney using conventional materials such as cement.

 

While the design is not ideal, it shows that chimney can be constructed with today’s technology from the materials that are commercially available now.

Download ETAB software file 1 for the design : please click here

A 5000m high chimney is designed with internal diameter 100m using different thicknesses on different height as shown in below ‘image 01’ .

Image 01

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MATERIAL USED

The materials used M400 grade concrete up to 2100m from bottom and M200 grade from 2100m to 5000m as shown in below’ image 02’.

 

 

 

                                                                                                         

 

 

 

Image 02

 

 

PHYSICAL PROPERTIES OF MATERIAL,

For M200 grade concrete,

 

 

For M400 grade concrete,

VERIFICATION OF PHYSICAL PROPERTIES,

The Modulus of Elasticity, E of the concrete can be verified as per codal provisions given in IS 456, clause no 6.2.3.1, pg no 16,

6.2.3.1 The modulus of elasticity of concrete can be

assumed as follows:

where

E, is the short-term static modulus of elasticity in

N/mm*.

 

The support conditions used in model are bottom fixed as shown in ‘image 03’   

Image 03


 

The wind load assigned in the analysis file is shown in the figure below ‘image 04’

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

WIND LOAD ASSINGED USING “USER LOAD” IN “AUTO LATERAL LOAD” DROPDOWN LIST AND ASSIGNED MANUALLY AS PER HEIGHT MENTIONED ABOVE.

Wind load is calculated   using formulae

Wind loading in N/m2 = 0.5*Air density ( Kg/m3)*(V m/s)2 * Drag coefficient for cylinder

Drag coefficient for cylinder = 0.7

Air density varies with height


 

Now, the thicknesses were updated many times and columns are provided for bottom 100 m part for stresses to come under the limit of factor of safety of 2,

The final physical form of the chimney is shown below with parts exploded for clarity

 

 

 

ANALYSIS DATA: -

After finishing the analysis and re doing it several times to reach our desired goal, we got following analysis results.

DEFLECTION RESULTS

HEIGHT (m)

DEFLECTION IN X- DIR(m)

DEFLECTION IN Y- DIR(m)

100

0.103

0.066

200

0.508

0.408

300

0.368

0.655

400

0.488

0.88

500

0.641

1.14

1000

2.067

3.07

1500

4.33

5.84

2000

7.47

8.2

2500

11.5

11.8

3000

14.7

15.4

3500

19.4

20

4000

24.7

25.4

4500

30

30.7

5000

35.4

36.7

 

 

 

SHELL STRESSES

HEIGHT (m)

Smax (MPa)

Smin (MPa)

SV   (MPa)

5000

11.35

-11.35

10.6

4500

8.73

-14.4

17.06

4000

7.23

-24.67

25.467

3500

7.23

-39.2

40

3000

6.267

-48.67

48.21

2500

6.37

-64.74

65.33

2000

5.16

-73.47

74

1500

5.2

-91.33

91.4

1000

2

-76.67

76

500

9

-70.7

72.7

200

12

-82.7

83

190

12.8

-85

84.2

180

14

-86

86

170

14.87

-88

88

160

16.7

-90

89.34

150

17.34

-94

92

140

22

-99.34

93.33

130

27.34

-101.4

98

120

39.34

-108

112

110

58

-143

148

100

67

-150

138

80

26

-81.34

77.4

60

18.6

-46

40.7

40

12

-32.7

30

20

12

-26.7

24.7

 

FINAL RENDER IMAGES

 

Untitled

Untitled3

Untitled2


 

Untitled1

 

Full Chimney  view

 

Old Flexible design: To see flexible design