T A B L E O F C O N T E N T S Chapter 1: Introduction

1.1 Project Introduction1.2 Aims and Objectives1.3 Limitations1.4 Equipment and Materials Used

Chapter 2: Truss Selection and Precedent Studies

2.1 Waddell ‘A’ Truss2.2 Terminology2.3 Joint and Member Analysis

Chapter 3: Material Specifications: Test and Analysis3.1 Material Test and Analysis3.2 Design Strategy3.3 Methodology

Chapter 4: Bridge Prototyping and Testing4.1 Bridge 1 4.2 Bridge 24.3 Bridge 34.4 Bridge 44.5 Bridge 54.6 Bridge 6

Chapter 5: Final Bridge Design5.1 Core Support5.2 Top and Bottom Chords5.3 Truss5.4 Strut5.5 Joint Analysis5.6 Construction Process5.7 Results and Analysis of Bridge Testing5.8 Calculations

Chapter 6: Conclusion6.1 Comparison of Load, Weight and Efficiency of Test Bridges and Final6.2 References

Chapter 8: Individual Case Studies (Task 1)8.1 Case 18.2 Case 2

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8.3 Case 38.4 Case 48.5 Case 5

C H A P T E R 1: INTRODUCTION1.1 P R O J E C T I N T R O D U C T I O N

In a group of five, this project requires students to build a perfect truss bridge by using fettuccine pasta as the material. Students were required to investigate the compression and the tension capabilities of the bridge with different types of joints and designs for the bridge. The students would be able to explore the

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different truss members using different arrangements to achieve the strongest. Throughout the project the students would be able to identify truss system and to be able to identify the best strength without exceeding too much weight so that the load would be evenly distributed.

The fettuccine bridge must be strong and efficient to achieve high efficiency – high load-bearing capabilities and minimal usage of materials – but within a clear span of 350mm. The formula for efficiency is as stated below:

Efficiency = Load supported by bridge(g)Weight of the bridge(g)

1.2 A I M S A N D O B J E C T I V E S

AimThe aim of this project is to develop the student’s understanding of tension and compressive strength of the construction materials and to understand the force of distribution in a truss. Also, to build a truss design with high aesthetic value whereas could use minimal amount of construction material and withstand a high amounts of loads.

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ObjectivesThe objectives of the project are:

To develop understanding on force distribution in a truss system; To develop in-depth understanding on tension and compressive strengths of the construction

materials; and To design and produce a fettuccine bridge of perfect truss with high efficiency and minimal

construction materials.

1.3 L I M I T A T I O N S

The most significant limitation in this project is the requirement that the overall weight of the fettuccine bridge cannot exceed 70 g. This encouraged us to approach the construction process and bridge design carefully, taking into account that the main objective is to produce a bridge of high load-bearing qualities using minimal materials. With that in mind, many bridge designs were explored to determine the most efficient design which can be constructed within the weight boundary of 70 g.

Other forms of limitation include the fact that water, the load used in bridge testing, will escape the pail when the suspended pail makes contact with the ground due to gravity. This will cause inaccuracy as the amount of water spilled cannot be determined and taken into account of. This scenario might not be fully preventable, but can be improved by suspending the pail closer to the ground so that the fall will be less impactful.

1.4 E Q U I P M E N T A N D M A T E R I A L S

1. Fettuccine

Fettuccine is the main material of the bridge. Every component of the bridge should be constructed

2. Glue

Glue is an important factor in constructing the fettuccine bridge as it connects and combines the

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only using fettuccine. Different fettuccine brands are explored to select the best fettuccine to construct the bridge.

different fettuccine members, especially at the joints. Different types of glues are experimented to determine the best type of adhesive.

3. Weighing scale

Weighing scale is used to determine the weight and load imposed on the bridge and individual fettuccine members.

4. Sandpaper

Sandpaper is used to smoothen rough edges of the fettuccine, providing more accurate lengths.

5. Cutting blade

Blade is used to cut and trim the fettuccine. It provides a cleaner and more precise cut as compared to using scissors.

6. Cutting mat

Cutting mat provides a flat and safe base to cut the materials.

7. Metal ruler

Metal ruler is used to measure the length of fettuccine needed to be cut. It is laid flat and side by side against the fettuccine to ensure accurate markings and prevent parallax error.

8. S-hook

S-hook is used to connect the pail to the fettuccine bridge during the load test. It is hooked onto a structural member of the bridge on one end, and the handle of the pail is hooked onto the other end.

9. Pails 10. Plastic cup

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Two pails are used to transfer water from one to another. One pail will be hung onto the S-hook attached to the bridge, and water will be gradually transferred into it from another pail on the ground.

Plastic cup is used to transfer water from one pail to another pail hooked on to the bridge.

11. String

C H A P T E R 2: TRUSS SELECTION & PRECEDENTS2.1 T H E W A D D E L L A T R U S S

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String is used to tie the S-hook on to the bridge during the final testing, allowing the pail to hover few inches from ground to prevent too much water from splashing out.

Figure 2.1.1: The Waddell ‘A’ Truss Bridge by John Alexander Low Waddell in Missouri, USA.

The Waddell "A" Truss Bridge in Parkville Missouri is also known as Linn 1898. The bridge was designed by engineer John Alexander Low Waddell and is the subject of a U.S. patent. The bridge was constructed and redesigned within 7 years. Hence, the bridge was reassembled using the same high standards as originally specified by the designers.

The Waddell ‘A’ bridge is a triangular-shaped steel truss bridge, as observed from its overall A-shaped form. It is supported with four panels, and it is a single span bridge that rests on two support links by connecting rivet units. The bridge is capable to support heavy traffic without excessive vibration.

2.2 B R I D G E T E R M I N O L O G Y

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2.3 J O I N T A N D M E M B E R A N A L Y S I S

The members of the Waddell A bridge along the top chord are in compression as they are supporting a downward force when load is applied, whereas the members along the bottom chord are in tension.The trusses and members between the top and bottom chords can be in compression or tensions, depending on the design, orientation and angle of the vertical member.

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Members in compression

Members in tension

Figure 2.3.1: The form of the bridge resembles is ‘A-shape’ and resembles a triangle.

Figure 2.3.2: Joint details of the Waddell A Bridge

Figure 2.3.3: Joint and truss details on the top chord of the Waddell A bridge

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C H A P T E R 3 : MATERIAL TEST & ANALYSIS3.1 M A T E R I A L A N A L Y S I S A N D S E L E C T I O N

To select the best materials and design to construct a bridge with high efficiency, many tests were conducted to determine a few aspects of the bridge in terms of:

1. Brand and length of fettuccine span2. Arrangement of fettuccine stack3. Type of adhesive

The aspects listed above are investigated to determine both compression and tensile strengths.

Compression strength test

Tensile strength test

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Compression strength is the maximum compressive force a material experiences before sustaining failure. Compressive strength is crucial and has to be taken into account of in bridge design. For the compressive strength experiment, each subject will be placed upon the weighing scale and secured into place by a wad of blu-tack. Without applying any force, its initial weight on the weighing scale is neglected and computed as zero. Force is then applied to the subject by pressing against the items on the weighing scale. The maximum weight recorded by the weighing scale before the subject breaks is documented.

Tensile strength is the maximum tensile force a material can sustain before failure. The bridge must be able to sustain a certain amount of tensile stress before fracturing. Hence, to determine tensile strength, each aspect of experimentation will be subjected to a tensile strength test, in which load will placed upon the subject and will be subsequently increased. The load will be increased until the subject experiences breakage, and the last recorded load will be documented in the unit of grams (g).

1. Brand and length of fettuccine

Figure 3.1.1: Kimball fettucine Figure 3.1.2: San Remo Figure 3.1.3: Arabella fettuccine

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This test will determine the most suitable brand of fettuccine to use in constructing the bridge with highest efficiency, and also the suitable length to determine how long should the bridge span be to sustain higher loads. The brands of fettuccine experimented are Arbella, Kimball and San Remo. All the brands will be tested in lengths of 7, 12, 17 and 22 cm against an increasing load.

Brand Length (cm)

Number of fettuccine per stack (unit)1 2 3 4 5

T C T C T C T C T CSR 7 270 250 900 800 1800 1500 3500 4000 3800 >5000KI 200 228 500 900 700 1600 2500 3645 2700 >5000AR 150 235 300 900 900 1500 2000 2356 4000 >5000SR 12 210 200 300 786 900 1499 1300 3427 2300 >5000KI 70 218 400 889 600 1430 800 4100 900 >5000AR 100 167 270 890 420 1267 900 2543 1700 >5000SR 17 120 78 260 675 715 1298 1200 3216 1950 >5000KI 135 60 230 688 400 1276 450 2354 1000 >5000AR 180 76 235 700 400 1208 700 1435 800 >5000SR 22 147 67 260 567 690 1100 1020 1321 1660 >5000KI 110 55 213 580 260 1125 679 3423 880 >5000AR 125 56 170 600 230 1187 543 1231 843 >5000

Key: SR = San Remo T = Tensile testKI = Kimball C = Compression testAR = Arbella

Analysis:From the tabulated data, we found that San Remo is the strongest fettuccine brand as compared to other alternatives like Kimball and Arbella.

2. Arrangement of fettuccine stack

Figure 3.1.4: (from right) I-beam, C-beam and triple-stack arrangement

Based on the previous analysis on brand and fettuccine length, San Remo fettuccine is then experimented using 12 cm span, but in different stack arrangement of C-beam, I-beam and horizontal stack.

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Arrangement Load sustained before breakage/gT C

C-beam 2416 4500I-beam 2268 <5000

Horizontal stack 1300 3850

Key:T = Tension test C = Compression test

Analysis:Tension testBased on the results found, the C-beam and I-beam is the most effective arrangement as it can sustain a load above 2 kg, as compared to the horizontal stack, the weakest arrangement, which can only sustain 1.3 kg. It is also noted that the C-beam tends to crumple internally when load is imposed, hence the I-beam is the more preferred option.

3. Type of Adhesive

Figure 3.1.5: UHU glue Figure 3.1.6: Super glue Figure 3.1.7: White glue

Besides the type of fettuccine, the type of adhesive used also plays an important role in constructing the perfect bridge. White glue, UHU glue and superglue is experimented.

Arrangement

Type of glueUHU Super glue White glue

T C T C T CC-beam 590 1432 1355 3482 530 1435I-beam 548 1234 1800 3525 547 1745

Analysis:The results are evident: super glue is the best adhesive. Super glue can sustain almost twice the load than other alternatives, whereas UHU glue and white glue is significantly weaker and requires a long time to dry.

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I-beam constructed using super glue can sustain a heavier load than the C-beam, making it a better, more efficient construction material.

3.2 D E S I G N S T R A T E G Y

Based on the tests conducted, we have decided to use the specifications below to create the bridge.

S P E C I F I C A T I O N R E A S O N I N GBrandSan Remo

Strongest brand of fettuccine (able to sustain highest loads)

SpanRange of 12-15 cm per span

Ideally, 3 spans should be used instead of 2. This is because

ArrangementI-beam

Strongest and most stable arrangement

AdhesiveSuper glue

Bonds fettuccine very strongly (fettuccine does not move out of place after application)

Shortest drying time Easy application

We have also realized that certain fettuccine brands are suitable for compression and certain brands of fettuccine perform better in tension. Hence, experimenting with materials has helped identify the impact of different arrangements and orientation on structural integrity of the bridge.

Theoretically, members in tension should be more reinforced and strengthened, especially the bottom chord of the bridge due to the downward force the load would impose, calling for the need to utilize I-beam structure as this is the strongest beam arrangement. Members in compression, such as the vertical trusses in between, might not require such a strong reinforcement, so other more lightweight materials and methods can be considered.

3.3 M E T H O D O L O G Y

Methodology is the documentation of the construction and testing process, including pre-test preparations.

Step 1: Preliminary studiesAn analysis on bridge typologies is conducted to determine the type of bridge to construct. The Waddell A truss is selected.

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Members in compression

Members in tension

Step 2: Material selection Materials used to construct the bridge are experimented by tension and compression tests. Results from the test are documented, and the best, highest performing materials are used to construct the bridge.

Step 3: ImprovisationsAfter determining the specifications we require of the bridge, we tried to improvise from the original Waddell bridge template by sketching out new modifications which could contribute to a higher efficiency.

Step 4: Pre-makingThe template of the bridge is then drawn out on A3 paper. This will ensure that the measuring and cutting of the fettuccine will be done more accurately, especially at the joints. The strips of fettuccine are also checked before the cutting process, and only the flat, straight members are used.

Step 5: Cutting processThe cutting process then commenced. The fettuccine strips are measured precisely using a metal ruler. Blade is used as opposed to scissors to ensure cleaner, straighter cuts. Joints and edges are carefully angled. For layers that require 2 or more strips, we ensure that the layers do not line up at the same spot to prevent breakage.

Step 6: Gluing processSuper glue is used to combine two layers of fettuccine strips, making the member stronger and abler to withstand greater load. As super glue dries very fast, precision is very important in this step. Therefore, the fettuccine members should be positioned appropriately and glued carefully, ensuring no gaps in between. After gluing, the bridge should be left aside to dry for at least 20 minutes before testing.

Step 7: Pre-testingBefore testing the bridge, its weight should be documented using a weighing scale, as this measurement is crucial in determining the overall efficiency of the bridge. Two tables of equal heights are placed next to each other with a gap of 350 mm to fulfil the 35 cm clear span criteria. Both tables are connected by the fettuccine bridge, which is placed at the edges of the tables. An S hook is also hooked on to the middle beam of the bridge, and a pail is then hooked onto the S hook. Prior to that, they should also be weighed, as their weight would be taken into account alongside other additional load to be included later.

Step 8: Applying the loadWater is supplied from the nearby washroom, and it is added into the pail carefully and gradually using a small cup. As the load increases, the bridge is observed for any deformities. The whole process is also videotaped so that the video could be reviewed to analyse the weak points of the bridge when it breaks.

Step 9: Determining the load sustainedAfter sustaining breakage, the amount of water in the pail attached to the bridge is weighed using the weighing scale. The actual load sustained is calculated by dividing the amount from the weight of the S hook and the pail.

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Step 10: Post-testing analysisThe video recording the testing process of the bridge is reviewed to analyse the failure points of the bridge. Deformities occurring at any point of load application is noted and highlighted on the diagram on paper. After a group discussion, improvisations are made and a new bridge is constructed and tested. Steps 4 to 10 are repeated for each new bridge design.

C H A P T E R 4 : BRIDGE TESTING4.1 B R I D G E 1

Bridge 1 has the simplest design, basically keeping to the original template of the Waddell A truss, with only a few modifications to test the original structural integrity of the bridge.

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S P E C I F I C A T I O N R E A S O N I N G1 35 cm total length Initially we thought that the total length of the

bridge should only be 35 cm, including clear span.

2 7 cm height Tall height as to keep to original A truss template.

Results

D I M E N S I ON S R E S U L T STotal height: 7 cm Total weight: 74 g

Load sustained: 2 kgEfficiency: 27.0 %

Total width: 6 cmTotal length: 35 cm including clear span

Analysis

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BREAKAGE POINT: core support in which the hook and load is placed

The shape of the bridge retains the original Waddell A truss without much modification, and we realize that the breakage point of the bridge lies at the core, as the rest of the bridge was in good condition and did not collapse internally. The core support has broken from the undistributed force imposed by the point load from the S-hook.

Improvements to be made Strengthen the core support and distribute the load carefully throughout the bridge.

4.2 B R I D G E 2

Learning from Bridge 1, the core support of the bridge is modified into an X bracing, so that the load can be distributed evenly throughout the bridge, reducing the stress on the point in which the S-hook is hung. However, the overall shape and dimensions of the bridge is retained, as we believed that only the core support is the most fragile member of the bridge.

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S P E C I F I C A T I O N R E A S O N I N G1 7 cm height Since the overall structure and shape of

Bridge 1 did not crumble or fracture from the load, we decided that the 7 cm height can be retained as reducing or increasing it would not cause any difference.

2 Horizontal X bracing for lateral support Learning from the failure of Bridge 1 – where the bottom support has broken - we decided to create an X bracing connecting both bottom chords in the middle to distribute the force more evenly throughout the bridge. The hook would be hung on the middle of the X.

Results

D I M E N S I O N S R E S U L T STotal height: 7 cm Total weight: 76 g

Load sustained: 5.2 kgEfficiency: 68.4 %

Total width: 6 cmTotal length: 35 cm including clear span

Analysis

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BREAKAGE POINT: Core support in which the load is imposed on

The main reason for failure in Bridge 2 does not lie in the structural integrity of the overall design, but rather the strength of the core support (beam where the hook is placed upon). Placing an X bracing across the bottom chords did not help as it still broke under pressure of the load, and this might be due to the weakness of the bracing.

Improvements to be made: Strengthen the X bracing, especially where the S hook is hung on, as this is the point which

receives the most stress.

4.3 B R I D G E 3

In Bridge 3, the horizontal X bracing is retained, but modified from the last bridge design. I-beams are used instead of triple-stacked fettuccine beams, in hopes to improve the strength and load-bearing capabilities of the X-bracing. The height of the bridge is also reduced to lower the center of gravity

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Figure X: Plan view and perspective view of Bridge 3

S P E C I F I C A T I O N R E A S O N I N G 1 5 cm height We attempt to reduce the height to give it a low center of

gravity, providing more stability. Height is also reduced to compensate the high usage of fettuccine members.

2 Overlapping horizontal members Due to the fettuccine’s limited length, two strips of fettuccine is the minimal requirement to create a 35 cm span bridge. For Bridge 1, to connect both spans of 17.5 cm, an additional shorter I-beam is glued to the sides, combining and overlapping both spans. Horizontal members are overlapped, assuming that this can make the horizontal load-bearing components stronger.

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3 Diagonal trusses Under the impression that horizontal members will accommodate most of the stress, vertical 4members are neglected, with only two diagonally placed members to sustain compressive forces.

4 X-bracing on horizontal members X-bracing is considered to distribute the forces evenly throughout the bridge instead of focusing on one single point in which the load will be placed.

5 Usage of I-beams instead of stack arrangement

I-beam is stronger than stacked fettuccine beams.

Results

D I M E N S I O N S R E S U L T STotal height: 5 cm Total weight: 76 g

Load sustained: 5.5 kgEfficiency: 72.4 %

Total width: 5 cmTotal length: 35 cm including clear span

Analysis

BREAKAGE POINT: I-beam on bottom chord and entire middle portion of the bridge

Bridge 3 is structurally stronger than Bridge 1 and 2, as three layers of I-beams are overlapped to create the bottom support. However, due to the lack of vertical members, the compression forces acting on the

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bridge cannot be dispersed. Also, I-beams required high usage of fettuccine (one I-beam required 4-6 strips of fettuccine), which in turn highly affected the weight of the bridge. The weight of Bridge 3 is 76 g, exceeding the weight criteria by 6 g.

Improvements to be made: Reduce the weight of the bridge to below 70 g Increase number of vertical members Aim to carry heavier load

4.4 B R I D G E 4

From Bridge 3, we realized that the extensive use of I-beams to improve structural strength of the bridge has effectively carried a heavier load, but the weight of the bridge has exceeded the requirement by 6 g. Hence, in Bridge 4, I-beams are only used in parts which are necessary. The reduction of I-beams is compensated with extensive reinforcement of trusses between top and bottom chords.

Figure X: Perspective and elevation of Bridge 4

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S P E C I F I C A T I O N R E A S O N I N G1 43 cm total length (35 cm clear span) The length of the bridge is elongated, with 4

cm extra length on each side, but the clear span remains at 35 cm.

2 Increased number of vertical members and trusses

Vertical members are increased to reinforce the trusses between top and bottom chords.

3 I-beams only used for bottom chord To minimize the weight of the bridge, I-beams are used at only the most critical areas of the bridge (bottom chord and core support).

Results

D I M E N S I O N S R E S U L T STotal height: 5.5 cm Total weight: 76 g

Load sustained: 7.5 kgEfficiency: 98.7 %

Total width: 6 cmTotal length: 43 cm (35 cm clear span)

Analysis

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BREAKAGE POINT: I-beam on the bottom chord

I-beams are only used for the bottom chords as the bottom chords receive the bulk of the load. However, the breakage point was still at the bottom chord, indicating that the bottom chord is still weak even though it is strong and rigid from the usage of I-beams. We analyzed the breakage point and found that the bottom chord was weakened by the joint connection between the truss and the bottom chord. This joint is stressed by the fact that the diagonal truss is not glued to the joint properly, resulting a higher stressed imposed on the vertical member, pressuring the particular joint, causing it to break.

Improvements to be made: Workmanship should be improved – ensure that all angled members are cut and glued precisely Reduce overall weight of the bridge Reduce joints connected to the bottom chord

4.5 B R I D G E 5

The overall weight of the bridge is quite an issue throughout the many bridge samples we have constructed. We have successfully reduced the weight to 72 g in Bridge 5, by reducing the number of vertical units in between the chords.

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Figure 4.5.1: Perspective view of Bridge 5

S P E C I F I C A T I O N R E A S O N I N G1 Reduced number of trusses To reduce overall weight of the bridge2 Reduced number of joints To reduce connection points which stresses

the bottom chords of the bridge

Results

D I M E N S I O N S R E S U L T STotal height: 5.5 cmTotal width: 4 cmTotal length: 42 cm

Total weight: 72 gLoad sustained: 8.4 kgEfficiency: 116.7 %

Analysis

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BREAKAGE POINT: Joint connection of core support to bottom chord

The load sustained by Bridge 5 is by far the highest at 8.4 kg. After a thorough inspection of the bridge, the area of failure seemed to lie at the connection point of the beam to the bottom chord (see highlighted diagram).

The cross-sectional face of the core support is connected to the web of the bottom chord. The I-beam member was cut too shortly as compared to its equivalent, non-direct load-bearing members. This shortage created a gap between the beam and the bottom chord, causing the beam to collapse.

Improvements to be made: Further reduce the overall weight of the bridge to be under 70 g to heighten efficiency Improve workmanship on cutting and trimming fettuccine members

C H A P T E R 5: THE FINAL BRIDGEBridge 6 is the final bridge used in the actual day of load test. We have made a few modifications based on the past test models we have explored, mainly on the truss direction and number of joints used in the structure. Each component of the fettuccine bridge will be explained extensively in this chapter.

5.1 C O R E S U P P O R T

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The core support is the first and direct recipient of external loads from the environment. Hence, it has to sustain direct stress and distribute it evenly throughout the bridge structure, indicating that this component has to be strengthened and reinforced carefully.

Figure 5.1.1: Elevation and perspective of the core support.

For the final bridge, the core support is constructed out of overlapping I-beams, with an extra layer of fettuccine for extra support and better form to accommodate the curvature of the S-hook. The core support is very short in length to minimize the tensile stress imposed on it, and it is layered onto the flange of the bottom chords instead of gluing to the web. When load is applied, the core support will not detach from the bottom chord easily and induce breakage.

5.2 T O P & B O T T O M C H O R D S

The top and bottom chords of the final bridge is made out of I-beams extensively. I-beams provide very high strength and stability which is crucial for sensitive components like the bottom chord, which directly absorbs the load distribution from the core support unit.

5.3 T R U S S

Instead of the previous design in Bridge 4 and 5, the trusses in the final bridge are modified. Diagonal trusses are inverted to form a triangular unit. This modification is done in consideration of the vertical member, which only comprises of a single fettuccine layer. By converging the diagonal trusses at one point,

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the vertical member, which experiences high compression forces, is now strengthened and supported on each side.

Figure 5.3.1: Truss design of the final bridge

5.4 S T R U T

The strut is the member which defines the width of the bridge and connects the one side of the bridge to another. In previous designs, struts are used extensively. However, in the final bridge, struts are kept to a minimum. Only 4 struts were used as they provide less load-bearing function as compared to other counterparts of the bridge. However, they are used to provide lateral support and prevent the top part of the bridge from collapsing inwardly.

Figure 5.4.1: Four struts are used in the final bridge design

5.5 J O I N T A N A L Y S I S

The final bridge design features a variety of joints used as connection points between different components of the fettuccine bridge.

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DIAGONAL TRUSS TO CENTRE TRUSSDiagonal trusses are angled towards the centre truss, forming a three-way connection point which effectively transfers the load throughout the bridge.

ANGLED JOINTThe angle between the top chord and bottom chord is 14.9 degrees. An acute angle calls for an angled joint on the top chord to

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TOP CHORD TO CENTRE TRUSSThe top chords, which are made out of I-beams, are cut at an angle. The cross-section provides ample surface area to connect the chord to the centre truss, which is also an I-beam. It is connected to the flange, a flat surface so that a stable joint can be formed.

I-BEAM LAYERINGFor the core centerpiece which sustains the highest and direct load, I-beam layering is used by stacking I-beams on top of each other.

CONVERGING TRUSSES ON THE TOP CHORDDiagonal trusses converge at the vertical truss and the top chord, forming a three-way connection point.

I-BEAM TO I-BEAM JOINTBeams are double-layered and are positioned between two I-beams to enhance the direct distribution of compressive force. Rather than putting the beams on top of the bottom chord, they are placed between the I-beams.

5.6 C O N S T R U C T IO N P R O C E S S

1. I-beams are constructed to be used for the bottom chord and top chord for the final bridge. The bottom chord is constructed first.

2. The central vertical member is added onto the bottom chord.

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3. The top chords are added to the structure, forming a triangle.

4. The vertical trusses are added within each half side of the triangle.

5. The diagonal trusses are fitted between the vertical truss members, forming small triangles within the triangular Waddell structure. 6. Four beams are added and positioned

perpendicularly to the web of the bottom chord.

7. Another triangular side of the bridge is added to the structure. Both sides are connected by the perpendicular beams.

8. Struts are added onto the top chord to secure the alignment of the triangular sides.

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9. The core support is inserted carefully into the structure, layered on top the flanges of the bottom chords.

5.7 A R R A N G E M EN T & L O A D D I S T R I B U T I O N I N F E T T U C C I N E B R I D G E

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Members in compression

Members in tension

I-beams are built using 6 strands of fettuccine: 1 for the flange on each side and 2 strands to form the web of the I-beam. The 1:2:1 formula is used in constructing the I-beam as it provides more rigidity to the structure, as the 2-layer web unit provides large surface area for contact with the perpendicular flange.

2-Layer fettuccine strips are used for the beams and struts. They are slotted in vertically to the groove of the I-beam. If the fettuccine strips are in a horizontal alignment, they will break easily when force is asserted.

1-Layer fettuccine strips are used for the vertical and diagonal trusses between the top and bottom chord. Force is not asserted severely onto the vertical and diagonal trusses, as the trusses support the top and bottom chord. They are also kept to a single layer as we aim to reduce the overall weight of the final bridge to meet the requirement of 70 g.

5.8 R E S U L T S & A N A L Y S I S O F B R I D G E T E S T I N G

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Figure 5.8.1: The final bridge

Results

D I M E N S I O N S R E S U L T STotal height: 5 cmTotal width: 4 cmTotal length: 42 cm

Total weight: 71 gLoad sustained: 12.1 kgEfficiency: 169.0 %

Analysis

BREAKAGE POINT: I-beam

The final bridge was designed to withstand more weight than the past test bridges. Through multiple test, we identified the key problem which lies on the use of compression and tension. Material wise, fettucine works well as a tensile member but when arranged in an orderly manner; I-beams, could withstand heavy compression. In our final bridge design, there were surprisingly more tensile members as compared to compression members. This was realized after calculation was carried out to determine the forces being withstood by each individual member and its role; whether compressive or tensile in the testing of the bridge. During the test, the final bridge first broke at the bottom chord which was a 42cm I-beam. This could

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be due to the lack of compressive force being transferred to the vertical members (one vertical member was known to not contribute at all with a reading of 0 force) stressing the long span of I-beam in the process. However, the final bridge managed to sustain a load of 12.1kg while being only 71 g; which was the lightest weight we have ever achieved resulting in an efficiency of 169.0 %. Albeit the many structural flaws, workmanship and strategic placement of members for force distribution played a significant role in the bridge test.

C H A P T E R 6 : C O N C L U S I O N6.1 C O M P A R I S O N B E T W E E N T E S T B R I D G E S A N D F I N A L

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1 2 3 4 5 final0

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40

60

80

100

120

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COMPARISON OF LOAD, WEIGHT AND EFFICIENCY BETWEEN TEST BRIDGES AND FINAL

sustained load (g/1000) bridge weight (g) efficiency level

As observed from the graph above, there is an upward trend of increasing efficiency as we improvised from the previous design.

The overall trend of bridge weight fluctuates between the range of 70 g to 76 g. Manipulating the overall weight of bridge is a very delicate and sensitive task, as adding or removing a strand of fettuccine might influence it. The overall bridge weight remained at 76 g for Bridges 2-4, exceeding the required maximum weight, but we gradually reduced the amount to a final weight of 71 g.

As for the load sustained by the fettuccine bridge, there is an increasing upward trend, indicating that we have successfully made positive progress with each new design. The first bridge design can only carry a load of 2 kg, but our final bridge managed to carry a load of 12.1 kg from the initial load of 2 kg, indicating that our final fettuccine bridge design is able to sustain a load increment of 83.5 %

Even with an overall flat trend of bridge weight, the successful increment in load-bearing ability has improved the efficiency of the bridge in every new design.

6.2 R E F E R E N C E S

1. Mystery Bridge Nr. 15: A Wadell A-frame Truss In Texas. (2012). Retrieved May 12, 2016, from http://thebridgehunter.areavoices.com/2012/11/27/mystery-bridge-nr-15-a-wadell-a-frame-truss-in-texas/

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2. Patent US529220 - Truss-bridge. (n.d.). Retrieved May 12, 2016, from http://www.google.com/patents/US529220

3. Truss bridge. (n.d.). Retrieved May 7, 2016, from http://dnr.mo.gov/shpo/nps-nr/90002173.pdf

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