STATIC & DYNAMIC ANALYSIS OF HYPERBOLIC COOLING TOWERS

STATIC & DYNAMIC ANALYSIS
OF HYPERBOLIC COOLING
TOWER

 Natural Draught cooling towers (NDCT) are very
common in modern day thermal and nuclear power
stations.
 Hyperbolic Reinforced concrete cooling towers are
widely used for cooling large quantities of water in
thermal power stations.
 Reinforced concrete natural draught cooling tower
(NDCT) are essential components of a power plant and
industrial set ups.

 NDCT are provided to evacuate the heat generated
during various processes in a thermal and nuclear power
plant into the atmosphere.
 With the advancement in the industrial sector and the
strict conformity to the pollution control regulations, the
cooling towers are becoming taller and NDCT of
greater than 150m have been constructed in our country.

 These structures being flexible are prone to earthquake
and wind forces.
 The static and dynamic characteristic of these
structures is therefore, a pre- requisite for their rational
and safer design.
 R/C cooling towers are huge structures and also show
thin shell structures.
 R/C cooling towers are subjected to its self-weight and
the dynamic load such as an earthquake motion and a
wind effects.

 Hyperbolic cooling towers are large, thin shell reinforced
concrete structures which contribute to environmental protection
and to power generation efficiency and reliability.
 Cooling tower is a device which converts hot water into cold
water due to direct air contact. It works on the temperature
difference between the air inside the tower and outside the tower.
 Natural draft cooling tower is one of most widely used cooling
tower. Hyperbolic shape of cooling tower is usually preferred
because of its strength and stability and large available area at the
base due to shape.

The most prominent component
of a natural draft cooling
tower is the huge towering
shell and columns.
Most commonly considered loads are;
Dead load(D)
Wind load(W)
Earthquake load(E)
Temperature variations(T)
Construction loads(C)
Settlement(S)

I Important elements of the shell include
 The columns at the base, which provide
the necessary opening for the air.
 The lintel, either a discrete member or
more often a thickened portion of the
shell, which is designed to distribute the
concentrated column reactions into the
shell wall.
 The shell wall or veil, which may be of
varying thickness and provides the
enclosure.
 The cornice, which like the lintel may be
discrete or a thickened portion of the wall
designed to stiffen the top against ovaling.

Bellary thermal power station (BTPS, Karnataka) is a power generating
unit near Kudatini village in Bellary district, Karnataka state.
 Two existing cooling towers are considered for case study. BTPS is
geographically located at 15º 11’58” N latitude and 76º 43’23” E
longitude.
 The Total height of the tower is 143.50 m. The tower has a base, throat
and top radii of 55 m, 30.5 m and 31.85 m respectively, with the throat
located 107.75 m above the base. (Unit No- 2 cooling tower, year of
construction= 2002).
 The Total height of the tower is 175.50 m. The tower has a base, throat
and top radii of 61 m, 34.375 m and 41.00m respectively, with the throat
located 131.60 m above the base. (Unit No- 3 cooling tower, under
construction).

1) To Study the linear static analysis of existing cooling
towers and intermediates cooling towers ( CT1, CT2,
CT3, CT4, CT5 ) for maximum principal stress with
varying the height and thickness.
2) To Study the comparison between two existing cooling
towers CT 1 (143.5m) & CT 5 (175.5m) height of
Bellary Power plant for different element types (8
noded SHELL 93 & 4 noded SHELL 63), and also by
varying mesh ratio.
3) To Study the Free vibration analysis for two existing
cooling towers CT 1(143.5m) & CT 5 (175.5m) height
with varying thickness.

4) To Study the Natural frequencies, modes of vibration (selected
modes) for both existing cooling towers CT 1 (143.5m) & CT 5
(175.5m) height.
5) To Study the frequencies, maximum principal stresses for two
existing cooling towers CT 1 (143.5m) & CT 5 (175.5m) height
subjected to earthquake excitation (ground acceleration).
6) To Study the deflection pattern, stress induced for both existing
cooling towers CT 1(143.5m) & CT 5 (175.5m) height subjected
to wind load for varying thickness.
7) To Study buckling pattern of two existing cooling towers CT
1(143.5m) & CT 5 (175.5m) height due to its self weight of the
towers for different modes of buckling with varying thickness.

8)To Compare all the analysis methods for both existing
cooling towers CT 1 (143.5m) & CT 5 (175.5m) height and
arriving at feasible method which shows less stress
concentration.
9) To Study the effect of earthquake and wind loads acting on
these existing cooling towers, and finding out the dominant
load.
10) To Find optimum (best suited) cooling tower among these
two existing cooling towers for different loads, stresses, &
keeping in mind the environmental protection.

Based on Objectives of the study. The following methodology has been set
for the project
1) Linear Static analysis (self weight or dead load)
2) Dynamic analysis (Earthquake & wind loading)
The cooling towers are analyzed using FEA (Finite element analysis).
ANSYS V.10 & ANSYS V 13.0 software is used for the analysis of these
shell structures. The element types used in the analysis are
1) 8 node SHELL 93
2) 4 node SHELL 63
 Seismic analysis is carried out for 0.5g, 0.6g, 0.7g ground acceleration in accordance
with IS codes. Wind loads on these cooling towers have been calculated in the form of
pressure by using the design wind pressure co-efficient and design wind pressure at
different levels as per IS codes.

1) G. Murali, C. M. Vivek Vardhan and B. V. Prashant Kumar Reddy
Vel Tech High Tech Dr. Rangarajan Dr. Sakunthala Engineering Colleges, Chennai, Tamil Nadu, India ARPN
Journal of Engineering and Applied Sciences VOL. 7, NO. 1, JANUARY 2012 “RESPONSE OF COOLING
TOWERS TO WIND LOADS”
2) Esmaeil Asadzadeh1 PROF. Mrs. A. RAJAN2 Mrudula S. Kulkarni3 SahebaliAsadzadeh4
“FINITE ELEMENT ANALYSIS FOR STRUCTURAL RESPONSE OF RCC COOLING TOWER SHELL
CONSIDERING ALTERNATIVE SUPPORTING SYSTEMS”
3) Prabhakar N. Technical Manager Gammon India, Prabadevi Bombay 18 January (1990) Technical session 4
paper no 9 in his paper “ STRUCTURAL DESIGN ASPECTS OF HYPERBOLIC COOLING TOWER”
MENTIONED DIFFERENT FEATURES OF R. C. HYPERBOLIC COOLING TOWER”.
4) Prashant N, Sayeed sulaiman
PG Student, Dept. of Civil Engg., Ghousia College of Engineering, Ramanagaram & Sayeed sulaiman
Asst Professor, Dept. of Civil Engg., Ghousia College of Engineering, Ramanagaram- Bangalore International
Journal of Emerging Trends in Engineering and Development Issue 3, Vol.4 (June-July 2013) in his paper “ TO
STUDY THE EFFECT OF SEISMIC LOADS AND WIND LOAD ON HYPERBOLIC COOLING TOWER
OF VARYING DIMENSIONS AND RCC SHELL THICKNESS”
5) A. M. El Ansary, A. A. El Damatty, and A. O. Nassef “OPTIMUM SHAPE AND DESIGN OF COOLING
TOWERS

4) Prashant N, Sayeed sulaiman
PG Student, Dept. of Civil Engg., Ghousia College of
Engineering, Ramanagaram & Sayeed sulaiman Asst Professor,
Dept. of Civil Engg., Ghousia College of Engineering,
Ramanagaram- Bangalore International Journal of Emerging
Trends in Engineering and Development Issue 3, Vol.4 (June-July
2013) in his paper “ TO STUDY THE EFFECT OF SEISMIC
LOADS AND WIND LOAD ON HYPERBOLIC COOLING
TOWER OF VARYING DIMENSIONS AND RCC SHELL
THICKNESS” carried out

1) This paper deals with study of hyperbolic cooling tower of
varying dimensions and RCC shell thickness, for the purpose of
comparison a existing tower is consider, for other models of
cooling tower the dimensions and thickness of RCC shell is
varied with respect to reference cooling tower.
2) The boundary conditions should be consider as been top end
free and bottom end is fixed. The material properties of the
cooling tower are young’s modulus 31GPa, Poisson's Ratio 0.15
and density of RCC 25 kN/m3 .

3) These cooling towers have been analyzed for seismic loads &
wind load using Finite Element Analysis. The seismic load will
be carried out for 0.5g, 0.6g& 0.7g in accordance with IS: 1893
(part 1)-2002 and by modal analysis and wind loads on these
cooling towers have been calculated in the form of pressures by
using the design wind pressure coefficients as given in IS: 11504-
1985 code along with the design wind pressures at different
levels as per IS: 875 (Part 3) - 1987 code.
4) The analysis has been carried out using 8-noded 93 Shell
Element. The outcome of the analysis is max deflection, max
principal stress & strain, max von mises stress & strains.

The main aim of analysis works on CT as follows. In the present
study FEA of 3CT viz CT1, CT2, CT3 has been carried out to
evaluate principle stress and strain, Von mises stress and strain
and deflection.
1) If dimension is less, deflection is also less and if dimension is
more, deflection also more.
2) The deflection in static analysis is least for CT2 comparison to
reference tower CT1 and CT3.
3) The principal stresses in static analysis i.e. (self weight) are
observed to be less for CT2 then the reference tower CT1.

4) In the free vibration analysis it has been observed that the
principal stress for the 1st mode is greater for CT1 than CT2 and
CT3.
5) It is evident from the seismic analysis. The principal stress
observed to be least for CT2 & CT3 comparison to reference
tower CT1.
6) It is evident from the seismic analysis that the deflection is the
least in CT2 & CT3 compare to reference tower CT1.
7) It is evident from the wind load analysis that the deflection is the
least in CT2. &principal stress is least in CT2 compare to the
reference tower CT1and CT3.

A thin shell is a curved slab whose thickness ‘h’ is small compared with its
other dimensions and compared with its principal radius of curvature.
The surface that bisects the shell is called the middle surface. It specifies
the form of this surface and the thickness ‘h’ at every point.
Analysis of thin shells consists the following steps:
 Establish equilibrium of a differential element cut from the shell
Achieve strain compatibility so that each element remains continuous with
each adjacent element after deformation.
Stress resultants and stress couples

1. Paraboloid of revolution
2. Hyperboloid of revolution
3. Circular cylinder
4. Elliptic paraboloid
5. Hyperbolic paraboloid
6. Circular cone

Introduction to fem
package
(ansys software)

 8 noded SHELL 93 element (ANSYS V 10 )
 4 noded SHELL 63 element (ANSYS V 13.0)
SHELL93 is particularly well suited to model curved shells. The
element has six degrees of freedom at each node: translations in the
nodal x, y, and z directions and rotations about the nodal x, y, and z-
axis.
The deformation shapes are quadratic in both in-plane directions.
The element has plasticity, stress stiffening, large deflection, and large
strain capabilities.

contd
The geometry, node
locations, and the
coordinate system for
this element.
The element is
defined by eight
nodes, four
thicknesses, and the
orthotropic material
properties. Mid side
nodes may not be
removed from this
element.
SHELL 93 geometry

1) Nodes: I, J, K, L, M, N, O, P.
2) Degrees of Freedom: UX, UY, UZ, ROTX, ROTY, ROTZ.
3) Real Constants: TK (I), TK (J), TK (K), TK (L), THETA, ADMSUA.
4) Material Properties: EX, EY, EZ, ALPX, ALPY, ALPZ (or CTEX, CTEY, CTEZ or THSX,
THSY, THSZ), (PRXY, PRYZ, PRXZ or NUXY, NUYZ, NUXZ), DENS, GXY, GYZ,
GXZ, DAMP.
5) Surface Loads: Pressures - Face 1 (I-J-K-L) (bottom, in +Z direction), face 2 (I-J-K-L)
(top, in -Z direction), face 3 (J-I), Face 4 (K-J), face 5 (L-K), face 6 (I-L).
6) Body Loads: Température – T1, T2, T3, T4, T5, T6, T7, T8
7) Special Features: Plasticity, Stress stiffening, large deflection, large strain, birth and death,
Adaptive descent

 SHELL63 has both bending and membrane capabilities.
Both in-plane and normal loads are permitted.
 The element has six degrees of freedom at each node:
translations in the nodal x, y, and z directions and
rotations about the nodal x, y, and z-axes. Stress
stiffening and large deflection capabilities are included.

1) Nodes I, J, K, L
2) Degrees of Freedom UX, UY, UZ, ROTX, ROTY, ROTZ
3) Real Constants TK(I), TK(J), TK(K), TK(L), EFS, THETA, RMI, CTOP, CBOT, (Blank),
(Blank), (Blank), (Blank), (Blank), (Blank), (Blank), (Blank), (Blank), ADMSUA See
Table 63.1: SHELL63 Real Constants for a description of the real constants
4) Material Properties EX, EY, EZ, (PRXY, PRYZ, PRXZ or NUXY, NUYZ, NUXZ), ALPX,
ALPY, ALPZ (or CTEX, CTEY, CTEZ or THSX, THSY, THSZ), DENS, GXY, DAMP
5) Surface Loads Pressures -- face 1 (I-J-K-L) (bottom, in +Z direction), face 2 (I-J-K-L) (top,
in -Z direction), face 3 (J-I), face 4 (K-J), face 5 (L-K), face 6 (I-L)
6) Body Loads Temperatures -- T1, T2, T3, T4, T5, T6, T7, T8
7) Special Features Stress stiffening, large deflection, Birth and death

ANALYSIS
PROCEDURE
AND
CALCULATIONS

Two Existing cooling towers are considered as case study
chosen from (BTPS, Karnataka).
Details of existing cooling towers
1) The Total height of the tower is 143.50 m. The tower has a
base, throat and top radii of 55 m, 30.5 m and 31.85 m
respectively, with the throat located 107.75 m above the
base.
2) The Total height of the tower is 175.50 m. The tower has a
base, throat and top radii of 61 m, 34.375 m and 41.00m
respectively, with the throat located 131.60 m above the
base.

 Boundary condition of the cooling tower has been
taken as: top end free and bottom end fixed.
 Material properties: young’s modulus 31GPa
 Poisson’s Ratio: 0.15
 Density of RCC: 25 kN/m3
 Shell element :
 8 node SHELL 93 &
 4 node SHELL 63

Where,
Ro is the horizontal radius at any vertical coordinate,
Y with the origin of coordinates being defined by the center of the
tower throat,
ao is the radius of the throat &
b is some characteristic dimension of the hyperboloid.

The seismic analysis are carried out for 0.5g, 0.6g & 0.7g ground acceleration in
accordance with IS: 1893 by modal analysis of the hyperbolic cooling towers, the earthquake
analysis of the shell is carried out by response spectrum method.
For the Calculation of the Design Spectrum, the following Factors were considered as per
IS 1893(Part I)-2002.
Zone factor: For Zone III = 0.16, as per table 2, pg16 IS 1893 (part 1):2002
Importance factor I = 1.75, as per table 2 & 5, pg 8 IS 1893 (part 4):2005
Response reduction factor R = 3, as per table 7, pg 23 IS 1893 (part 1):2002
Average réponses acceleration coefficient Sa/g =Soft soil site condition, as per clause 6.4.5,
pp16 IS 1893 (part 1):2002

0.5 g 0.6 g
0.7 g
RESPONSE SPECTRA GRAPHS

VARIATION OF HOURLY MEAN WIND SPEED WITH HEIGHT
CT 1
CT 5

GUST FACTOR AND WIND PRESSURE CALCULATIONS:
CT 1: Existing Cooling tower (BTPS)
Cy =10, as per clause 8.3, pp 52 IS 875 (part 3)-1987.
Cz =12m, as per clause 8.3, pp 52 IS 875 (part 3)-1987.
Lh = 1700, from fig 8, pp50 IS 875 (part 3)-1987.
gfr = 0.85, from fig 8, pp50 IS 875 (part 3)-1987.
fo = natural frequency = 0.8210858, as per clause 7, pp48, IS 875 (part 3)-1987.
Damping Value (β) = 0.016, as per table 34, pp52 IS 875 (part 3)-1987.
Table: Gust factor result for CT1
H B X, Fo S Cz x h/
Lh
B Ф fo x Lh/ E SE/p GF
9.2 103.6 9.4 3.24 0.04 0.065 0.71 0.1791 49.84 0.04 0.1 1.886
29.2 90.4 2.6 8.75 0.041 0.206 0.7 0.1778 42.44 0.042 0.107 1.883
49.2 78.7 1.3 13.68 0.044 0.347 0.7 0.1778 39.39 0.045 0.123 1.889
69.2 69.3 0.8 18.6 0.045 0.488 0.68 0.1752 38.08 0.047 0.132 1.88
89.2 63 0.6 23.24 0.03 0.63 0.65 0.1713 36.9 0.048 0.09 1.842
108.47 61.9 0.5 27.59 0.025 0.766 0.61 0.166 36.03 0.048 0.075 1.808
134.33 63.7 0.4 33.42 0.03 0.948 0.61 0.166 35.24 0.05 0.093 1.817

Table: ANSYS input result of wind pressure for CT1
Degrees
(θ)
F(N/mm2)
Height (m)
9.2 29.2 49.2 69.2 89.2 108.475 134.33
0 0.000434 0.00023 0.000278 0.000296 0.000773 0.000319 0.000334
15 0.00026 0 0 0 0.000464 0 0
30 -0.00035 -0.00084 -0.00097 -0.00104 -0.00062 -0.00111 -0.00117
45 -0.00104 -0.00179 -0.00209 -0.00222 -0.00186 -0.00239 -0.00251
60 -0.00148 -0.00239 -0.00278 -0.00296 -0.00263 -0.00319 -0.00334
75 -0.00182 -0.00287 -0.00334 -0.00356 -0.00325 -0.00382 -0.00401
90 -0.00191 -0.00299 -0.00348 -0.00371 -0.0034 -0.00398 -0.00418
105 -0.00148 -0.00239 -0.00278 -0.00296 -0.00263 -0.00319 -0.00334
120 -0.00061 -0.0012 -0.00139 -0.00148 -0.00108 -0.00159 -0.00167
135 -0.00087 -0.00155 -0.00181 -0.00193 -0.0015 -0.00207 -0.00217
150 -0.00078 -0.00143 -0.00167 -0.00178 -0.00139 -0.00191 -0.00201
165 -0.00078 -0.00143 -0.00167 -0.00178 -0.00139 -0.00191 -0.00201
180 -0.00078 -0.00143 -0.00167 -0.00178 -0.00139 -0.00191 -0.00201

CT 5 (175.5m): Existing cooling tower (BTPS)
Cy =10, as per clause 8.3, page no-52 IS 875 (part 3)-1987.
Cz =12, as per clause 8.3, page no- 52 IS 875 (part 3)-1987.
L h = 2000, from fig 8, page no-50 IS 875 (part 3)-1987.
Gfr = 0.8, from fig 8, page no-50 IS 875 (part 3)-1987.
fo = natural frequency = 0.699320, as per clause 7, page no-48, IS 875 (part 3)-1987.
Damping Value (β) = 0.016, as per table 34, page no-52 IS 875 (part 3)-1987.

Table: ANSYS input result of wind pressure for CT 5

ANALYSIS STEP INVOLVED IN FINITE ELEMENT
MODELLING:
PREPROCESSING: DEFINING THE PROBLEM
1. Give example a Title
Utility Menu > File > Change Title ...
/title, CT
2. Create Key points
Preprocessor > Modeling > Create > Key points > In Active CS
3. Define Lines
Preprocessor > Modeling > Create > Lines > Lines > splines Line
4. Symmetrical model
Preprocessor> Modeling>Operate>Extrude>line>About Axis
5. Define Element Types
we have used 8 noded shell93.
6. DEFINE REAL CONSTANT
Preprocessor > Real Constants... > Add...

7.DEFINE ELEMENT MATERIAL PROPERTIES
Preprocessor > Material Props > Material Models > Structural >
Linear > Elastic > Isotropic
In the window that appears, enter the following geometric properties
Young's modulus EX:
Poisson's Ratio PRXY:
Density:
8.MESH
1. Define Mesh Size
Preprocessor > Meshing > Manual Size > Size Controls > Lines > picked
Lines...
2. Mesh the frame
Preprocessor > Meshing > Mesh > Area > click 'Pick All'.

SOLUTION: ASSIGNING LOADS & SOLVING
1. Define Analysis Type
For Static analysis:
Solution > New Analysis > Static
For Modal analysis:
Solution > New Analysis > modal
For Spectrum analysis:
Solution > New Analysis > spectrum
2. Apply Constraints
Solution > Define Loads > Apply > Structural > Displacement > On Nodes
3. Apply Loads
Solution > Define Loads > Apply > Structural > Force/Moment > Inertia
force> Gravity> Global
4. Apply Pressure
Solution > Define Loads > Apply > Structural > Pressure > Elements
5. Solve the System
Solution > Solve > Current LS

GENEREL POSTPROCESSING: VIEWING THE
RESULTS
1. To view the element in 3D rather than a line:
Utility Menu > Plot Ctrls > Style > Size and Shape
2. View the deflection contour plot.
3. View the stress and strain in contour plot

 Comparison of cooling towers (CT 1, CT 2, CT 3, CT 4,
and CT 5) with varying heights and thicknesses.
 Comparison of cooling towers (CT 1, CT 2, CT 3, CT 4,
and CT 5) with varying heights & thicknesses along with
varying mesh ratio.
 Comparison between two existing cooling towers (CT 1 &
CT 5) for different element types (8 node SHELL 93 & 4
node SHELL 63).

Fig -Key points to create CT Fig –Nodes numbering in CT
Fig -Element numbering Fig -Geometric model with BC
Fixed at
base

UNDEFORM EDGE
DEFORM EDGE
MAX
DEFLECTION
VALUE
Deflection of CT 1 for 200mm shell thickness

MAX
PRINCIPAL
STRESS
VALUE
MAX
PRINCIPAL
STRAIN
VALUE

MAX VON
MISES
STRESS
VALUE
MAX VON
MISES
STRAIN
VALUE

MAX DEFLECTION
VALUE
UNDEFORM EDGE DEFORM EDGE
Deflection of CT 5 for 200mm shell thickness

Graphical Representation of Stress v/s Height for Maximum principal
stress for CT 1, CT 2, CT 3, CT 4, and CT 5 for 200mm shell thickness

Graphical Representation of Height v/s Element types for various
principal stresses between CT 1& CT5 for 200mm shell thickness

Fig: Max Principal Stress for CT1 Fig: Max Principal Strain for CT1
Fig: Von Mises Stress for CT 1 Fig: Von mises Stress for CT1

Results of Modal Analysis for CT 1 (143.50 m)

Results of Modal Analysis for CT 5 (175.50 m)

Graphical Representation of stress v/s thickness between CT 1
and CT 5 (Mode 1)

SEISMIC ANALYSIS
SEISMIC ANALYSIS FOR 0.5g FOR CT 1 (143.50 m)
DEFORM
EDGE
UNDEFORM EDGE

Fig: Max Principal Stress for CT1 Fig: Max Principal Strain for CT1
Fig: Von mises Stress for CT1 Fig: Von mises Stress for CT1

SEISMIC ANALYSIS FOR 0.5g FOR CT 5 (175.50 m)

Fig: Max Principal Stress for CT 5 Fig: Max Principal Strain for CT 5
Fig: Von Mises Stress for CT 5 Fig: Von Mises Strain for CT 5

Results of spectrum analysis for CT 1 (143.50 m)

Results of spectrum analysis for CT 5 (175.50 m)

Graphical Representation of stress v/s thickness between CT 1& CT 5 for 0.5g,0.6g ,0.7g
0.5g 0.6g
0.7g

Graphical Representation
of stress v/s thickness for
CT 5 for 0.5g, 0.6g, 0.7g
Graphical
Representation of stress
v/s thickness for CT 1 for
0.5g, 0.6g, 0.7g

WIND ANALYSIS Wind pressure applied on CT 1 (200mm
thickness)

Fig: Max Principal Stress for CT 1 Fig: Max Principal Strain for CT 1
Fig: Von Mises Stress for CT 1 Fig: Von Mises Strain for CT 1

Fig -Deflection at Top for CT 1 Fig -Deflection at bottom for CT 1
Fig -Deflection at Top for CT 5 Fig -Deflection at bottom for CT 5

Results of Wind Analysis for CT 1 & CT 5

Graphical
Representation of
stress v/s thickness for
CT 1 & CT 5 for wind
analysis
Graphical
Representation of
Deflection v/s
thickness between
CT1 & CT 5 for
wind analysis

BUCKLING ANALYSIS FOR CT 1(143.50 m)

Fig -Max Principal Stress (Mode 1) Fig -Max Principal strain (Mode 1)
Fig -Von mises stress (Mode 1) Fig -Von Mises Strain (Mode 1)

BUCKLING ANALYSIS FOR CT 5 (175.50 m)

Graphical
Representation of
stress v/s
thickness between
CT1 &CT5 for
buckling (Mode 1)
Graphical
Representation of
stress v/s thickness
between CT 1 & CT 5
for buckling (Mode 3)

Graphical
Representation of
stress v/s
thickness between
CT1 &CT5 for
buckling (Mode 5)
Graphical Representation
of stress v/s thickness
between CT 1 & CT 5
for buckling (Mode 10)

Graphical
Representation of
for Static, Modal,
Spectrum (0.5g), and
Buckling analysis for
cooling tower 1
(143.5m) for 200mm
thickness
Graphical
Representation of
for Static, Modal,
Spectrum (0.5g),
and Buckling
analysis for cooling
tower 5 (175.5m)
for 200mm
thickness

1) On Comparing all cooling towers (i.e. CT 1, CT 2, CT 3, CT 4, CT 5)
in static analysis (self weight of tower), CT 3 & CT 4 shows least
Maximum Principal stress among all cooling towers and prove to be
the optimum cooling towers for shell thickness of 200mm.
2) The Maximum Principal stress for two existing cooling towers (CT 1 &
CT 5) shows high value by using 4 noded SHELL 63 element as
compared to 8 noded SHELL 93 element.
3) In free vibration analysis for both existing cooling towers
a) As thickness of shell increases, Maximum Principal Stress goes on
increasing for CT 1 at TOP region in mode 1.
b) As thickness of shell increases, Maximum Principal Stress gradually
decreases from throat to bottom region for CT 5 in and TOP remains
minimum.

4) In Modal analysis, On comparing CT 1(143.5m) & CT 5 (175.5m) cooling towers,
CT 5 shows less maximum principal stress with increasing thickness (mode 1), and
stress shifts from throat to bottom region.
5) In Modal analysis, the Natural frequencies for CT 1 are more as compared to CT 5
with increasing thickness and for selected modes. (Mode1, Mode 5, Mode 10).
6) In Response spectrum analysis for 0.5g, 0.6g, 0.7g ground acceleration
a) The variation of Maximum Principal Stress for CT 1 of 200mm and 250mm
thicknesses are minimum and maximum respectively whereas, CT 5 behaves
conversely.
b) The variation of Maximum Principal Stress for CT 1 of 300mm, 350mm
thicknesses are maximum & minimum respectively whereas, CT 5 behaves
conversely.
7) In Response spectrum analysis maximum principal stress for CT 1& CT 5 are same
for 400mm thickness and shows optimality.
8) In Wind analysis, as thickness increases, deflection & maximum principal stress
decreases for both existing cooling towers (CT 1 & CT 5).

9) In Wind analysis, the degree of distortion increases with height of tower, hence
deflection is maximum in CT 5.
10) In Buckling analysis, the buckling of CT 1 is maximum as compared to CT 5, CT 5
shows less buckling due to its size, symmetric geometry of shell ( for increasing
thickness).
11) In Dynamic analysis, wind loads are dominating as compared to earthquake forces
in zone III.
12) On Comparing CT 1 & CT 5 for all analysis (methods) CT 5 gives optimum results
for all analysis and is best suited cooling tower.

RECOMMENDATIONS FOR FURTHER STUDIES
1) Thickness greater than 500mm can be selected and analyzed.
2) Thermal stresses and its variation along thickness and height can be analyzed.
2) Non linear analysis can be applied to the above studies.
3) Time history analysis can also be carried out for the earthquake analysis for
cooling towers considered in this project.

REFERENCES
1) G. Murali, C. M. Vivek Vardhan and B. V. Prasanth Kumar Reddy “RESPONSE OF
COOLING TOWERS TO WIND LOADS”, ARPN Journal of Engineering and
Applied Sciences, VOL 7, NO 1, JANUARY 2012 ISSN 1819-6608.
2) Esmaeil Asadzadeh, Prof Mrs A Rajan, Mrudula S Kulkarni, Sahebali Asadzadeh
“Finite element analysis for structural Response of cooling tower shell considering
alternative supporting systems” ,IJCIET, Volume 3, Issue 1, January- June (2012), pp.
82-98
3) N Prabhakar (Technical Manager), Bombay “Structural aspects of hyperbolic
cooling tower”, National seminar on Cooling tower, jan1990, Technical session IV,
paper no 9
4) Prashanth N, Sayeed sulaiman, “To study the effect of seismic loads and wind load
on hyperbolic cooling tower of varying dimensions and RCC shell thickness” :
International Journal of Emerging Trends in Engineering and Development Issue 3,
Vol.4 (June-July 2013) ISSN 2249-6149.

5) A. M. El Ansary, A. A. El Damatty, and A. O. Nassef, “Optimum Shape and Design
of Cooling Towers”, World Academy of Science, Engineering and Technology 60 2011.
6) Dr. S. N Tande Associate Professor & Head, Department of Applied Mechanics,
Walchand College of Engineering, Sangli, Maharashtra, India. Snehal. S. Chougule
Research Scholar, Department of Applied Mechanics, Walchand College of
Engineering, Sangli, Maharashtra, India. “Linear and Non linear Behavior of RC
Cooling tower under Earthquake loading”, International Journal of Latest Trends in
Engineering and Technology (IJLTET), VOL 2 Issue 4 July 2013, ISSN: 2278-621X
7) Shailesh S. Angalekar, Dr. A. B. Kulkarni, “Analysis of Natural Draught Hyperbolic
Cooling tower by Finite element method using Equivalent plate method”, International
Journal of Engineering Research and Applications (IJERA) ISSN:2248-9622
WWW.ijera.com vol 1, Issue 2, pp.144-148
8) Sabouri-Ghomi, Farhad Abedi Nik, Ali Roufegarinejad, Mark A Bradford,
“Numerical study of the Nonlinear Dynamic behavior of RCC towers under Earthquake
Excitation” ,Received: 8 September 2005; Received revised form: 17 January 2006;
Accepted: 17 January 2006.
9) D. Makovicka, “Response Analysis of RC cooling tower under seismic and wind
storm effect”, Acta Polytechnic Vol. 46 No. 6/2006.

10) Dynamic of structures by Anil .K .Chopra.
11) Design of Reinforced Concrete shells and folded plates by P.C. Varghese.
12) Advance reinforced concrete design by N Krishnaraju.
13) ANSYS Mechanical APDL Structural Analysis guide & ANSYS Reference Guide
14) Structural Engineering Handbook by Gould, P. L and Kratzig, W.B, “Cooling Tower
Structures” Ed Chen Wai-Fah Baco Raton: CRC Press LLC, 1999
15) Technical Specification for cooling water ozone generation plant REV00,
VOLUME II B & III, 1×700 MW Bellary 3 STPP, Specification n0- PE-TS-367-174-
14000-A001, Bharat Heavy Electrical limited

1) IS: 11504:1985.CRITERIA FOR STRUCTURAL DESIGN OF
REINFORCED CONCRETE NATURAL DRAUGHT COOLING
TOWER, New Delhi, India: Bureau of Indian standards.
2) IS: 875 (Part3):1987. CODE OF PRACTICE FOR DESIGN
LOADS (OTHER THAN EARTHQUAKE LOADS) FOR
BUILDINGS AND STRUCTURES. New Delhi, India: Bureau of
Indian Standards.
3) IS 1893 (part 1): 2002 CRITERIA FOR EARTHQUAKE
RESISTANT DESIGN OF STRUCTURES.
4) IS 1893 (part 4):2005 CRITERIA FOR EARTHQUAKE
RESISTANT DESIGN OF STRUCTURES. PART-4 INDUSTRIAL
STRUCTURES INCLUDING STACK-LIKE STRUCTURES

STATIC & DYNAMIC ANALYSIS OF HYPERBOLIC COOLING TOWERS

STATIC & DYNAMIC ANALYSIS OF HYPERBOLIC COOLING TOWERS

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