How to build the Super Chimney?
Author of the Design is Brajesh Chandra, M.S., ME retired Chief Engineer from KANPUR , IndiaThe 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
Full Chimney view
Old Flexible design: To see flexible design
 |