“Oh GOSH! Reflecting on Hackteria's Collaborative Practices in a Global Do-It...
Assignment 3 6504
1. ASSIGNMENT/ASSESSMENT ITEM COVER SHEET
Student Name: Donald HEATHER
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Student Number: Email: donald.heather@det.nsw.edu.au
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E D U C 6 5 0 4 Engineering Education Studies 1
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Campus of Study: Callaghan (eg Callaghan, Ourimbah, Port Macquarie)
Assessment Item Title: Engineering Scenario Due Date/Time:
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Lecturer/Tutor Name: C Hollis
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2. D. HEATHER - C2008809
CONTENTS PAGE
RESEARCH
Current pylon technology-P3
Types of trusses-P3
Types of pylons-P5
Forces on pylons-P6
Why use a truss-P6
Joining methods-P7
Test methods-P7
Design and development-P8
Results and conclusion-P17
Bibliograpthy-P18
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3. D. HEATHER - C2008809
RESEARCH
Current Pylon Technology
Pylon is the Greek term for monumental gateway of an Egyptian temple. A pylon is usually
tapered from bottom to top to support something like power lines. A transmission tower is a tall
structure used to support power lines usually made out of steel lattice. The four main functions of
towers are suspension, terminal, tension and transposition towers. The towers have prototypes
tested at tower-testing stations. The towers can be assembled on the ground and then erected using
push pull cables. Assembled vertically helicopters can be utilised as aerial cranes.
Pylons can also be used to support bridges, and can reach heights that rival some of the tallest
buildings. They are used in suspension bridges and cable staged bridges. The use of the pylon, as
a simple tower structure, has also been used to build rail road bridges.
TYPES OF TRUSSES
Warren Truss
The warren truss was patented by James Warren in 1948. It is one of the most popular designs
which use equilateral triangles to spread out the load on the bridge. The forces on the members
are minimalised due to the triangles being in compression and tension. As a load moves over the
bridge sometimes the forces switch in the members from compression to tension. This happens
especially to the members near the centre of the bridge.
.
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4. D. HEATHER - C2008809
Pratt Truss
Pratt trusses have the vertical compression members and diagonal tension members. The end
members are the only ones that do not slope towards the centre of the truss configuration. The
diagonal members are subjected to tension forces only so they can be thinner allowing for a more
economical design.
Howe Truss
The Howe Truss is the opposite of the Pratt Truss with the diagonal members slanting towards the
closest bridge end. These members are subjected to compressive forces which necessitate large
steel members. This makes this type of truss uneconomical for steel construction.
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5. D. HEATHER - C2008809
TYPES OF PYLONS
Pylons are tower-like structures that support antennas or electrical cables, or used as the vertical
support for a bridge or a tower.
Lattice Tower
These towers are made from steel and are a very practical type of pylon. They can be climbed by
hand to be serviced or modified and are easy to maintain. Different types of pylons do not allow
for climbing so the need to service the pylon must be done by crane or by lifts.
Monopole.
A monopole pylon is a single tall pole with an antenna on the top.
Wired Pylons
If a single pole pylon becomes extremely tall then supporting cables are connected in each
direction around the pole to stabilise it. Wired pylons are also called guyed towers.
Electric Pylon
Electric pylons are designed on the lattice tower model, with two or three sets of vertical arms to
hold the wires.
Bridge Pylons
Suspension bridges use the pylons as tall supports that hold up the cables of the bridge. They are
constructed deep into the ground, with large concrete foundations. Pylons may be positioned at
either side of the bridge providing a formal entrance.
Egyptian Pylons
Pylons in Egypt were large structures that marked the entrance to temples. They were strong
enough and high enough to provide a defensive barrier.
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6. D. HEATHER - C2008809
PYLONS IN CIVIL STRUCTURES
Pylons are utilised on civil structures to support a variety of needs.
Bridges: used to support the base of the bridge or be utilised to hold cables to support the bridge.
Power Lines: used to support power lines in different configurations and quantities of lines.
Aeronautics: used to support structures on aircraft such as navigation equipment.
Telecommunication: used for many types of electronic communication including radio, EMS
services, cellular and global positioning satellite technology.
FORCES ON PYLONS
Axial force – is the tension or compression force acting on a member. The axial force acts
through the centroid of the member and is called concentric loading. If the force does not act
through the centroid it is called eccentric loading. Eccentric loading produces a moment in the
beam because the load is a distance away from the centroid.
Radial Forces-This is a force that is exerted perpendicular to the centreline, or axis of an object.
WHY USE A TRUSS
A truss is a frame made up of a number of members, generally arranged in triangular units,
through which forces are transmitted to the joints called nodes. (Rochford, 2011)
Truss members need to be long and slender, the moments transmitted to these joints are negligible
and the nodes can be considered as hinges. Trusses are stronger than other structures because
nearly every material is much stronger in compression and tension than shear, torsion or bending.
Truss design pylons can be constructed on the ground and then lifted into position which is cost
effective.
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7. D. HEATHER - C2008809
JOINING METHODS OF TRUSSES
Gussit plate-A gusset plate is a steel sheet that is used to connect beams and girders to a column or
to connect truss members to the top or bottom plate. They can be fastened to a permanent member
by rivets, bolts or welding. They serve to join the members together and strengthen the joint in the
process.
Gang nails-Roof trusses can have gang nails in the nodes. These are made out of galvanised steel
to resist rusting and are hammered into members at the join.
TEST METHOD
I used a piece of steel clamped to the table with a long range dial indicator. The dial had a
magnetic base to secure it in position. I placed a piece of wood on the moveable jaw of the vice to
give me some height to allow indicators to rest up against. I then fitted the pylon, set the dial on
both zeros. The dial was set on zero and the clock dial was also on zero. As the vice was wound
in I could measure how far and feel the pressure needed to overcome the initial resistance, the
flexibility of the structure and finally failure length in mm. When I was winding I could feel the
resistance in the pylon, when the pylon members began to bent I could feel the pressure needed on
the vice handle decrease until the structure finally fractured. I had time to stop winding the vice
and read the measurement on the dial indicator at these three points in the exercise.
Vice with dial set up to take reading.
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8. D. HEATHER - C2008809
DESIGN AND DEVELOPMENT
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14. D. HEATHER - C2008809
DESIGN 1
I tried to construct a simple design
to complete the task. Difficult to
assemble with little room left in the
top of the caps. The result was a
very sturdy structure. Materials
were 10 Popsicle sticks, 2 caps and
5 pins. I am concerned about the
pins splitting the sticks which
would weaken the structure.
When the vice was tightened it
became hard to compress the pylon.
With extra force the members
cracked below the pins. There was
little flexibility in this pylon as it
was sturdy up until fracture.
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15. D. HEATHER - C2008809
DESIGN 2
The 3 sets of sticks were easy to assemble. The result was a sturdy
structure which I was hoping the axial force could be centred
between the 3 vertical pairs. Materials were 10 Popsicle sticks and
2 caps.
When the vice was tightened it was hard to compress, then the structure began to fail with less
pressure needed. This was compressing the structure resulting in bowing of vertical members in
an outwards direction. Continued winding of the vice resulted in fracture in middle of exposed
vertical member.
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16. D. HEATHER - C2008809
DESIGN 3
Attempted to construct a pylon design which utilised four vertical members. This made it difficult
to add supporting members between verticals because of a lack of material. This was difficult to
assemble as the four joint members had to be exactly a square to fit into cap. Materials used were
10 Popsicle sticks and glue.
When the vice was tightened it was hard to compress, then the structure began to fail with less
pressure needed. The structure continued to bow until failure in the middle of vertical member.
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17. D. HEATHER - C2008809
RESULTS AND CONCLUSIONS
DESIGN 1 DESIGN 2 DESIGN 2
INITIAL RESISTANCE 3mm 2mm 2mm
FLEXABILITY 3mm-5mm 2mm-11mm 2mm-8mm
COMPRESION FRACTURE 5mm 11mm 8mm
These results allow me to work out the percentage distance each design allowed before fracture.
Strain=compression length x 100
original length 1
Design 1
5/120 x 100/1=4.16%
Design 2
11/120 x 100/1= 9.16%
Design 3
8/120 x 100/1=6.66%
The construction of the 3 pylons in different configurations led me to believe Design 1 would be
the best. Design 2 and 3 were similar and I believed they would be less stable. The results were
design 1 was the hardest to wind in, resisted more force, however, it had no flexibility and
fractured quickly with no allowance to absorb the axial force. Designs 2 & 3 resisted at first then
allowed the vice to be wound in with less effort. This was absorbed by the members in
compression which resulted in the members bending until failure. The design 3 four member
pylon bowed in and out where the 3 member pylon all members bowed out from the centre which
allowed more travel on the axial plane.
In conclusion I can see a use for all types for different reasons. Design 1 could resist a greater
force and Design 2 & 3 could absorb forces that could be calculated so the pylon would be elastic
and return to original condition.
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