1. 3
Bachelor of Science (Hons) (Architecture)
Building Structures
(ARC 2523)
Project 1:
Fettuccine Truss Bridge
Nadia Othman 0303423
Siti Munirah Zazarin 0312710
Tan Lo Ming Marvin 0302352
Tan Woan Tyng 0312725
Wong Ai Ling 0303742
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Introduction
General Purpose of the Project
This project aims at evaluating, exploring and improving attributes of construction through designing an
efficient truss bridge. This is done through the exploration of different truss systems and construction
material (fettuccine), adhesives, as well as types of joints. By applying our understanding of tensile and
compressive strengths of the construction material, we then simultaneously gain a better understanding
of force distribution in the bridge constructed. Throughout the project, we are able to calculate load
distribution in a truss system. By doing so, we are then able to identify which members need to be
strengthened in terms of either tension or compression.
Project Outline
In a group of 5, we are to construct a bridge using only fettuccine and adhesive materials
(glue). The bridge constructed has a limitation of maximum weight 150g and 600mm clear
span. It is then tested using a point load. The hypothesis is that the higher the amount of load
carried, the more efficient the bridge. Also, the lighter the bridge, the higher its efficiency.
These are what we aim to achieve for maximum efficiency. This report consists of a precedent
study - The Taylor-Southgate Bridge. In this case study, we look the bridge’s connections,
arrangement of each member and how forces are transferred throughout the truss bridge. Sets
of testing results and development of our designated bridge through several trial-and-error
experiments and failure analyses are included.
Furthermore, calculations on the given questions and of the truss bridge itself are also
included.
Bridge Requirements
600mm clear span and maximum weight of 150g.
Only fettuccine and glue are allowed.
Loads have to be point load; focus on one specific point of the bridge.
Must be able to withstand each weight that is put on for 10 seconds.
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Methodology
In completing this project, the following methods are carried out:
Precedent Study
To give us a better understanding of a truss bridge, precedent studies are referred to. The
connections, arrangement of members and truss type are focused on. Based on our precedent
study findings, we then adopt desired features into our own truss design.
Material and Adhesive Strength Testing
Before constructing the bridge, we must first understand the physical properties of fettuccine.
Hence, we have tested the behaviour of the materials when subjected to either tension or
compression. These attributes are taken into consideration when designing our bridge.
Model Making
At the beginning of the designing process, simple sketches of the truss are made. Once a
design is decided on, we then generated it on AutoCAD. In constructing the bridge, these CAD
drawings of 1:1 scale are printed out to ease the process other than helping create a more
accurate model.
Structural Analysis
The truss is analysed by defining which members are tension and which are compression. The
structural analysis of our bridge is done using the same method as that of the truss analysis
exercises (appendix). Alternatively, we have also used bridge simulator softwares to calculate
the forces.
Working Schedule:
24 March 2014 Forming a group
5 April 2014 Testing on the strength of material (fettuccine) and
different adhesives
7 April 2014 Begin to design truss
12 April 2014 Final decision of design and first model making
16 April 2014 First model making
19 April 2014 First model making and testing
23 April 2014 Second model making
26 April 2014 Second model making and testing
27 April 2014 Final model making and strengthening
28 April 2014 Final fettuccine bridge testing and submission
Table 1: Working Schedule
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Equipment & Materials:
Fettuccine
Fettuccine is the main material used in making the bridge.
A ‘quality check’ is done on the material by separating the flat
fettuccine pieces with deformed ones. This enabled us to work
more efficiently.
Weights
Weights are used to determine the strength of the fettuccine bridge by
applying it as the point load on the bridge when testing the final
model.
Water bottles
Water bottles of two different sizes (500ml and 1.5l) are used as loads in the
test models. These are equivalent to 500g and 1.5kg.
S hook
The S hook is used to connect the fettuccine bridge
to the load (weights/water bottle) at the center of
the bridge. In our test models, a plastic bag is used
to hold the water bottles (load).
Plastic bag
Attached to S-hook to hold load.
Super glue
Use to hold fettuccine together. The reason we
have chosen this glue is because it can
adhesive in instant and also its high strength.
Kitchen Balance and Electronic Balance
Measuring equipment used for weighing our bridge to ensure it does not exceed the allowed
weight. Initially, a kitchen balance was used. However, we found that the recordings were
inaccurate, hence ended up weighing the bridge electronically.
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Precedent Study
Taylor-Southgate Bridge
To help give us a better understanding of a truss bridge, we have carried out a
precedent study on the Taylor-Southgate Bridge.
Main span length: 850 feet
Total length: 1,850 feet
Number of lanes: 4
Type of truss: Warren through truss with verticals
History
The Taylor-Southgate Bridge connects Newport, Kentucky to Cincinnati, Ohio and
spans the Ohio River. It carries U.S. Route 27. It opened in 1995, replacing the old Central
Bridge. The Taylor-Southgate Bridge was first proposed in the mid-1980s as a connection
between Main Street in Covington, Kentucky and Third Street Cincinnati, Ohio. It was designed
to relieve traffic from the adjacent Roebling Suspension Bridge. The crossing was named after
James Taylor, Jr. and Richard Southgate, two early settlers of Newport. It has four automobile
lanes an 850ft. central span, two pedestrian sidewalks, two approach spans of slightly different
lengths, and two piers in the river.
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Taylor’s Southgate Bridge is a prime example of a warren truss with verticals. A warren
truss consists of equilateral or isosceles triangles which minimizes the forces to only
compression and tension. Warren trusses commonly range from 150 ft. to 300 ft. When a load
moves through across a bridge, the forces on the members switch from compression to
tension. Most Warren trusses consist of verticals to limit the length of the floor system panels
and the unsupported length of the top chord. The verticals alternate in being tension members
and compression members. They carry insignificant load in a through truss but full live load in a
deck truss.
Figure: K-truss top chordFigure: Warren truss portal bracing
Figure: Interior view of bridge
Figure: Exterior View of bridge from afar
Warren Through Truss
Figure: Interior View of bridge from afar
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Joints
Taylor’s-Southgate Bridge mainly makes use of rigid connections with gusset plates.
Figure: Warren truss with verticals
Figure: Connection of web members to chord via gusset plates
Figure: Connections of portal bracing Figure: Connections for bracings of bottom chord
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Analysis
Strength of Material
i. Experimenting with Fettuccine
Experiments were conducted to determine the strength of the
fettucine. Different beam types as well as laminations were tested at a
minimum load of 500g, as seen in the table below. Different types of
adhesives were also tested in order to decide which be the best choice when
constructing the bridge.
Looking at the results, it can be concluded that the I-beam made up of 5 pieces of fettuccine is
strongest among all as it did not break, even after one minute. The laminated 4-layered fettuccine also
proved quite sturdy. The C-beam, L-beam and joists, on the other hand, either buckled or twisted when
tested. From this, we have chosen to use I-beams and laminated fettuccine in our bridge.
Out of the three types of adhesive tested, super glue turned out to be the best option, hence it
is what we have opted for in our construction process.
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Mock-Up Trusses
Before deciding on which truss type to apply in our design, we have tested out miniature trusses of the
same scale to see how they perform under a minimum load of 500g.
Howe Truss
500g - did not break
800g - bends and breaks at connections
Pennsylvania Truss
500g – bends, very bad deflection
Slanted Warren Truss
500g – breaks at 7 seconds
The type of trusses we decided to work on are the Howe truss and the Warren truss combined. Though
we feel that the Pennsylvania truss is high in aesthetic value, it is low in tension as its tension members
deflected upon testing. After much consideration, the following truss design is generated:
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Mockup Façade 1
The very first façade we made was constructed
by overlapping pieces of fettuccine on top of one
another. Instead of using whole strands of
fettuccine, they were cut short as separate
pieces. This turned out to be an unsuccessful
joint solution as it made the facade fragile,
making it difficult for force to be distributed. To
solve this problem, we came up with the following
solution.
The Solution:
Butt Joints
We resolved that each member should be joined with one another
using butt joints as it allows the façade to become levelled, hence
enabling force to be distributed evenly along the members. Also,
we found that the fettuccine is stronger when in Elevation B (image
below) rather than Elevation A, especially once laminated.
Therefore, we made this modification to help strengthen our bridge.
Mockup Façade 2
After completing one of the bridge facades, we
encountered a problem. We found that the
weight of that one façade itself was already
70g. Assuming the other façade is of the same
weight, we predict that the bridge altogether
would be >150g. We then had to simplify the
design to meet the project requirements.
Separate pieces of fettuccine
Overlapping the joints caused
unevenness
Elevation A
Elevation B
One façade weighed 70g – too heavy
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The Solution:
To reduce the weight of our bridge, we reduced the number of members in the truss. We also reduced
the length of the bottom chord as we felt that sides of 30mm each are sufficient in supporting the weight
of the bridge.
ii. Test Model 1
After resolving the issues faced, we then constructed our first complete bridge and proceeded with the
load testing. We added a 500ml water bottle at each interval to represent a load of 0.5kg.
Since the load tested is a point load, we decided to reinforce the middle. A 3-piece laminated fettuccine
is used at the very center.
Test Load (kg) 10-second test
1 0.5 ✔
2 1.0 ✔
3 1.5 ✔
4 2.0 ✔
5 2.5 ✘
74mm
30mm
Test Results
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The efficiency of the test model is:
( )
= 33.3
Based on our understanding of efficiency, our hypotheses are:
The heavier the bridge, the lower its efficiency.
The higher the load held, the higher the efficiency.
In other words, in calculating efficiency, the weight of the bridge is inversely proportional to the load it is
able to carry.
It is observed that our bridge is quite low in efficiency. In order to improve on its efficiency, we must
attempt to reduce its weight and increase its load-bearing ability.
Failure Analysis
We observed that the bridge failed at the very center. We found
that the whole bridge was still intact, but the laminated fettuccine
pieces we used to join the two facades together came off. We
believe that this happened either because the glue was not
completely dry when tested or that the butt joint was weak,
hence the member could not support the weight put onto it.
Apart from the I-beam falling off, we
found that the curve at the lower part
of the bridge split into two. After
having a closer look, we realized that
the member broke where our butt
joints connected to one another.
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iii. Test Model 2
Based on how the bridge failed in the previous test model, we decided to further strengthen the center
of the bridge. As observed in our ‘strength of material’ experiments, I-beams proved to be the strongest;
hence we decided to incorporate this beam type into our bridge. We used two I-beams at the center of
the bridge and placed them close to one another.
Center of the bridge:
Two I-beams, placed close to one
another
Side of bridge:
Supported using an I-beam
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Test Results
( )
When comparing this test model to the previous one (efficiency
score 33.33), it is 2 times more efficient. This indicates that all
changes made help improve the structural properties of the bridge.
Failure Analysis
When testing Test Model 2, the bridge was quite stable at 1 kg. However, the tension members started
deflecting at this point but did not break.
After reaching the maximum load (3.2 kg), the bridge snapped in half right in the middle. Unlike in Test
Model 1, the I-beam was still intact and still attached to the bridge. From this finding, we know that the I-
beams are strong but were placed too close to each other (load cannot be distributed evenly).
Test Load (kg) 10-second test
1 1.5 ✔
2 2 ✔
3 2.5 ✔
4 3 ✔
5 3.5 ✘
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Final Bridge Model
Having done several test models, the critical members of the truss are identified, hence
resulting in several design decisions. Members of the bridge are strengthened in accordance with
their chances of failure upon load application. This is done by laminating the fettuccine pieces as
such:
Most critical members – 3 layers of fettuccine
Less critical members – 2 layers of fettuccine
Least critical members – 1 layer of fettuccine
Based on the previous test model, it is observed that the compression members needed to be
reinforced. It is also observed that although the tension members showed deflection, they did not
break.
On the basis of this observation, we laminated the bridge as such:
When making changes to the bridge, we had to address the fact that our bridge was already at
maximum weight (150g). Thus, to enable us to add bracings for added support, we chose to
reduce the width of the bridge from the initial 7cm to 5cm. Having done this, our bridge achieved
a final weight of 147g.
7cm
5cm
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We believe that one of the causes of failure in Test Model 2 was that it lacked compression
members. Hence, the following addition was done to the upper façade (top part) of the Final Model:
With these added bracings, we predict the bridge to be able to carry more load than previously
achieved.
Seeing that the bridge failed in the middle in Test Models 1 and 2, we chose to stick to
our decision of using I beams in the center of the bridge. This time round, the two beams were
placed further apart from one another to enable force to be distributed more evenly.
Another modification made to the Final Model is that instead of joining the two facades together
using butt joints, we chose to overlap them. This is because we predict that by overlapping the
horizontal members, it would reduce the chances of them breaking off.
Base of Bridge
I-beams placed further apart from each other
(compared to Test Model 2)
Upper Façade of Bridge
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Bridge Testing
Tension
members begin
to buckle right
after the 1kg
weight is added
to the current
weight of 2kg.
Top chord
(compression
member) begins
to deflect at
around 6
seconds into the
testing.
The bridge
snaps at around
8 seconds.
The bridge
breaks into two
equal parts.
Snippets from Video of Bridge Testing
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Failure Analysis
As expected, the bridge, once again failed in the
middle. This time round, as the bridge did not
have a defined ‘center’, we had to attach the
hook to cling film which we wrapped around the
two I-beams. In our previous testing, the tension
members deflected but did not break. On the
day of the actual testing, a few of the tension
members failed as they snapped, quite close to
the joints. As observed in the time lapse
diagram, the members which show deflection
are those located either close to the center
Test Results
The efficiency of the final model is as follows:
( )
= 61.22
As a means of comparison, previous test models are looked at to identify the ‘best bridge’. The
performance of each bridge is recorded in the table below:
Test Model 1 Test Model 2 Final Model
Weight of bridge (g) 150 150 147
Maximum load held (kg) 2.5 3.2 3
Efficiency 33.33 68.27 61.22
Referring to the above table, it can be concluded that Test Model 2 observed the ‘most desired’ qualities
in a truss bridge.
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Truss Analysis
For analyzing purposes, only the upper part of the bridge (the Warren truss with verticals) is looked at.
The diagram below indicates the members in tension, compression, as well as members that are
neutral.
Calculation of the forces in the bridge members are found on the following pages.
Bridge Details:
Weight of bridge: 147g
Clear Span: 598mm
Length (Top Chord): 598mm
(Bottom Chord): 649mm
Width of base: 50mm
Height: 73mm
To cross-check our observations and findings, an online bridge simulator called Bridge Designer is used
to help calculate the amount of load exerted by each member. Through our observation, it is concluded
that our truss analysis values (calculations done) are quite similar to the simulation below.
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Suggestions of Improvement
Improvement 1
Figure: Diagram of forces acting on each member
Our failure lies in addressing the compression members. Initially we thought that all diagonal
members were tension members, thus we only applied one layer of fettuccine. It turns out that some
diagonals especially in the center, where load is mostly applied are actually compression members.
This weakens the center part as fettuccine is weak in compression.
Figure: Load being applied,
diagonal members being
compressed
Figure: Warping of
compression members
Figure: Members break off
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Improvement 2
During the final model testing, we did observe warping tension members, but did not address
the issue as the bridge broke due to the butt joints while the tension members remain intact. To improve
the model, we would cut down one layer of the arch, reducing it to two layers instead of three to reduce
the weight and thicken the diagonal members to two layers.
Figure: Suggested improvement to the bridge
Improvement 3
After completing the structural analysis of the bridge, it is resolved that the vertical members
do not add to the strength of the bridge, but instead adds weight. To increase its efficiency, the verticals
can be removed from the truss system.
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Conclusion
In general, we managed to keep the bridge under the 150g weight limit with a load capacity of
3kg. Our personal 5kg target was not met due to misinterpretation of load on the respective members.
We realized that it is significant to identify the truss form, joints and as load members early on to
increase work productivity. Moreover, use of adhesive and workmanship is important to ensure the
members are strong and do not crack halfway. Via this project, we have all learnt to manipulate
fettuccine to its potential in constructing a bridge. To further increase our understanding, we did
structural analysis regarding our truss to identify our mistakes. Despite failing the meet our aimed
target, we have all gained significant knowledge regarding truss design which will prove to be beneficial
in our future architectural paths.
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References
Boon, G. (2011). Warren Truss. Retrieved April 4, 2014 from:
http://www.garrettsbridges.com/design/warren-truss/
Lecture 15B.5: Truss Bridges. (n.d.). Retrieved May 1, 2014 from:
http://www.haiyangshiyou.com/esdep/master/wg15b/l0500.htm
Taylor Southgate Bridge (US27). (n.d.). Retrieved April 20, 2014 from:
http://bridgestunnels.com/bridges/ohio-river/taylor-southgate-bridge-us-27/
