TABLE OF CONTENTS
MODEL AND ANALYSIS OF THE COMMUNICATION TOWER ...................................... 1
GEOMETRY OF STRUCTURE: .......................................................................................... 1
LOAD COMBINATIONS: .................................................................................................... 3
EFFECT OF WIND LOADS: ................................................................................................ 3
REACTION AT THE SUPPORTS: ....................................................................................... 3
MAXIMUM FORCES IN THE MEMBERS: ....................................................................... 4
MAXIMUM FORCES IN THE CONNECTIONS: .............................................................. 5
BEHAVIOUR OF STRUCTURE IN CYCLONE: ................................................................ 6
MAXIMUM DISPLACEMENT AT POSITION OF ANTENNA: ....................................... 9
REDUCTION OF DISPLACEMENT BY 25%: ................................................................. 10
LIST OF FIGURES:
Figure 1: GEOMETRY OF OVERALL STRUCTURE ............................................................ 1
Figure 2: GEOMTERY OF MAST ............................................................................................ 2
Figure 3: MAST AND CABLE SECTIONS ............................................................................. 2
Figure 4:LOAD COMBINATIONS ........................................................................................... 3
Figure 5: REACTION AT THE SUPPORTS ............................................................................. 4
Figure 6: MAXIMUM FORCES IN THE MEMBERS ............................................................. 5
Figure 7: MAXIMUM FORCES AT THE END OF CABLES ................................................. 6
Figure 8: APPLICATION OF WIND LOAD ............................................................................ 7
Figure 9: APPLICATION OF ANTENNA LOADING ............................................................. 9
Figure 10: MAXIMUM DISPLACEMENT AT THE POSITION OF ANTENNA .................. 9
ABSTRACT
The design and analysis of a communications tower using SAP2000 are presented in this study.
The goal of this project was to create a tower design that is physically safe and effective while
also meeting the demands of the telecommunications sector. The 60.5m-tall tower was built to
support a number of antennas, ladder systems, mounting steelwork, and feeders.
The tower design sought to maximise materials for strength, flexibility, and effective
construction. It was built on a steel-framed system with reinforced concrete core walls. The
design procedure complied with industry norms by following the design standards provided in
AS3995-1994 and AS4100-1990.
The structural model of the skyscraper, developed using SAP2000, accurately reflected the
structure's geometry and component characteristics. A thorough analysis was performed, taking
into account the dead loads and wind loads on the mast, ladder, antennas, mounting steelwork,
and feeders. Regional and topographic considerations were used to compute the design wind
pressures at various heights.
The structural performance of the tower in terms of strength, stiffness, and stability was proved
by the analysis findings. The member forces and deformations that were measured gave us
important information about how the tower behaved under various load scenarios. To assure
the integrity and safety of the skyscraper, the findings directed the design optimisation process.
The report gives a thorough analysis of the design process with a focus on the unique
considerations and outcomes pertinent to the telecommunication tower.
MODEL AND ANALYSIS OF THE COMMUNICATION
TOWER
GEOMETRY OF STRUCTURE:
Our structure is mast. The terms mast and tower are used interchangeably, but
structurally the difference between them is that tower is self-supporting while mast is supported
by stays or guys or we can say cables. The mast is made of hollow sections. Different hollow
sections have been used for different elements based on the load, they are supporting.
Figure 1: GEOMETRY OF OVERALL STRUCTURE
The blue structure is mast and the green supporting it is guys or cables.
The next picture is showing the geometry of mast itself.
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Figure 2: GEOMTERY OF MAST
Mast and Cable sections
The Sections were selected according to the code AS 4100.
•
•
•
vertical members hollow circular section of 165.1x3.5 CHS was used.
Horizontal and bracing Section 42.4x4 CHS was used.
Cable of diameter 28 mm was used.
Figure 3: MAST AND CABLE SECTIONS
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LOAD COMBINATIONS:
We have applied two main load types.
•
•
Wind Load
Antenna Load
Similarly different load combinations have been used, which were taken from Australian codes.
Figure 4:LOAD COMBINATIONS
EFFECT OF WIND LOADS:
The mast experiences lateral forces from the wind, which deflect it and cause bending
moments. The mast structure may experience severe strains as a result of these lateral loads.
The magnitude of the lateral loads is influenced by variables such wind direction, wind speed,
mast geometry, and the environment.
Dynamic mast vibrations caused by wind loads can result in oscillations and resonance
occurrences. The equipment linked to the mast may experience pain or functional problems as
a result of these vibrations, which may also negatively affect the structural integrity of the mast.
To reduce these dynamic effects, proper analysis and design considerations are crucial. On the
mast, wind loads may cause overturning moments.
REACTION AT THE SUPPORTS:
The stability of a mast's structural system is greatly influenced by the response at its
supports. The supports distribute the mast's weight to the foundation or other structure below.
Depending on the configuration and loading conditions, the reactions at the supports can be
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classified as vertical forces, horizontal forces, and moments. To make sure that the supports are
built to resist the applied stresses, a proper study of these reactions is crucial. The reactions
have an impact on the mast's deflection, stability against overturning, and overall performance
in addition to its structural behaviour. It is essential for the safe and dependable operation of
the mast to carefully take support reactions into account. In the attached picture below, the
reactions at the supports have been shown.
Figure 5: REACTION AT THE SUPPORTS
MAXIMUM FORCES IN THE MEMBERS:
For their design, members like beams, columns, and braces must have their maximum
forces determined. Usually, applied loads like wind, gravity, and dynamic forces cause these
forces to occur. Engineers may make sure that the members are sized correctly and can safely
sustain the applied loads by analysing the maximum forces. In this examination, the member's
ability to withstand compression, tension, bending, and shear forces is assessed. The overall
integrity and safety of the mast are ensured as well as structural integrity by accurately
calculating the maximum forces.
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Figure 6: MAXIMUM FORCES IN THE MEMBERS
MAXIMUM FORCES IN THE CONNECTIONS:
Connections, such as bolts, welds, or fasteners, play a crucial role in the structural
structure of a mast. To ensure the capacity and dependability of connections, the maximum
forces in each must be determined. The design configuration, material qualities, and applied
loads including wind and dynamic forces have an impact on these forces. To ensure that they
can transfer forces between structural parts safely, engineers can choose the right connection
types, sizes, and materials by accurately analysing the maximum forces in connections.
Engineers can avoid connection failures, maintain structural stability, and improve the mast's
overall performance by appropriately accounting for these forces.
Reactions forces at the end of guys are shown below:
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Figure 7: MAXIMUM FORCES AT THE END OF CABLES
BEHAVIOUR OF STRUCTURE IN CYCLONE:
Due to the tremendous wind loads and dynamic pressures it receives in such severe
weather, a mast's behaviour in cyclones is of vital importance. Complex interactions between
the mast's structural elements, such as its beams, columns, and cables, are necessary for the
mast to respond to a cyclone. High wind speeds, gusts, and shifting wind directions, which
result in significant lateral loads and bending moments, must be tolerated by the mast. By
restricting excessive deflections and lowering dynamic vibrations, the cables, which are
frequently utilised for support and stability, are essential in minimising the mast's reaction to
cyclonic forces. To guarantee the mast and cables' capacity to endure cyclonic forces, maintain
structural integrity, and defend against probable failure or collapse, proper design and analysis
are crucial.
We have applied the cyclone loading and the antenna loading on the structure and check its
reaction.
There are different possibilities of direction in which the wind is acting. Let’s say if wind is
coming from the direction that 2 out 3 guys are in tension and are taking the loads but one out
of them will not take any load, which corresponds to different critical cases.
Wind loads:
The wind load was applied according to AS 1170.2. According to this standard the wind load
acting on the lattice tower is:
Fd = Cd x Az x qz
Where
Cd = drag coefficient
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Az = the Area of the members at the front face at a height z projecting normal to the face
The wind load is applied in the form load patches because as with the height of the tower the
load effect also increases. For this model the wind load is applied in the form of patches of 10
m.
Load detail is given as
Highest point
(m)
10
20
30
40
50
60.5
Loads (kN/m)
165.5x3.5 CHS
0.0342
0.16
0.39
0.74
1.25
1.77
42.4 x 4 CHS
0.008
0.046
0.113
0.216
0.365
0.55
Figure 8: APPLICATION OF WIND LOAD
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Figure 9: Wind Load
Figure 10: Wind Load 3
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Antenna loads:
Figure 11: APPLICATION OF ANTENNA LOADING
MAXIMUM DISPLACEMENT AT POSITION OF ANTENNA:
When designing a mast, the maximum displacement at the location of the antenna is a
crucial factor, particularly in regions subject to strong winds or seismic activity. Numerous
variables, including as wind speed, gusts, structural dynamics, and the flexibility of the mast
and its supporting structure, affect this displacement. The performance and operation of the
antenna may be impacted by excessive displacement, which could result in signal loss or
disruption. Engineers therefore carefully examine the maximum displacement to make sure the
antenna stays within reasonable bounds. This analysis looks at the stiffness and damping
properties of the mast as well as the efficiency of vibration control devices or dampers in
preventing excessive movement and preserving the operational integrity of the antenna.
The maximum displacement at the position of antenna in our case has been shown in the picture
that has been extracted from the Sap2000.
Figure 12: MAXIMUM DISPLACEMENT AT THE POSITION OF ANTENNA
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REDUCTION OF DISPLACEMENT BY 25%:
The displacement at the position of antenna can be achieved by 25% using following
techniques:
1. Boost Structural Stiffness:
Make the mast and supporting structure more rigid. Using sturdier materials,
expanding the cross-sectional sizes of parts, or adding more bracing or reinforcing features can
all help achieve this.
2. Enhance Foundation Design:
Make sure the foundation is properly planned to offer adequate stability and reduce
unwarranted movement. This could entail expanding the foundation's size or depth, using
specialised foundation technologies, or applying soil improvement procedures.
3. Damping system:
Install dampening mechanisms such friction dampers, adjusted mass dampers, or
viscous dampers. These systems have the ability to disperse energy and lessen vibrational
amplitude, which reduces antenna displacement.
4. Aerodynamic considerations:
Optimise the mast's aerodynamic design to reduce wind-induced forces and the displacements
they cause. The cross-sectional form may need to be changed, streamline fairings added, or
vortex shedding suppression techniques used.
5. Active Control system:
Implement active control systems, which use sensors and actuators to actively counteract
motions caused by the wind. These devices have the ability to detect vibrations and instantly
apply opposing forces to lessen displacement.
6. Regular examination:
Make sure the mast receives routine examination and maintenance to spot and repair
any deterioration or damage that can compromise its rigidity and performance.
How to do it in sap2000:
Once you model your structure in sap2000, run the model and find the displacement at
the position of antenna. Once you get the displacement, then follow the following steps to
reduce the displacements by 25%:
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1. Implement Structural Modifications:
To raise the overall rigidity of the mast, modify its structural qualities by enlarging its
members, including more bracing, or stiffening its connections. Implement these changes in
the SAP2000 model.
2. Repeat Analysis:
Analyse again to determine the displacement response by running the dynamic analysis
once more with the updated structure. If the displacement has decreased by the necessary 25%,
analyse the results to confirm.
3. Iterative Process:
If the intended displacement reduction is not realised, repeat the analysis and iteratively
tweak the structural alterations until the required displacement reduction is realised.
4. Validate and confirm:
Confirm that the altered structure satisfies the relevant design standards and safety
specifications. To guarantee that the redesigned mast stays within permissible stress and
displacement limits, carry out further testing.
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