SCHOOL OF ARCHITECTURE, BUILDING & DESIGN Research Unit for Modern Architecture Studies in Southeast Asia Bachelor of Science (Honours) (Architecture) Building Structures (ARC 2523) Prerequisite: Building Construction 2 (ARC2213)
Project 1 Fettuccine Truss Bridge Tutor : Pn. Nor Ita Johar Name & Student ID : 1. Andrew Chee Kiong Chee Man Shing 2. Lee Qin Ni 3. Meera Satheesh 4. Nicholas Lai Ken Hong 5. Vendy William
(0316202) (0317554) (0317062) (0317435) (0316944)
CONTENTS 1. Introduction 1.1 General purpose of study 1.2 Report preview 1.3 Restriction 1.4 Working schedule 2. Methodology 2.1 Precedent study 2.2 Making of fettuccine truss bridge 2.3 Structural analysis 3. Precedent Studies 3.1 Chambers Railroad Bridge 3.2 Waddell "A" Truss Bridge 4. Equipment & Material Analysis 4.1 Materials used and types 4.2 Material strength analysis 4.2.1 Type of fettuccine 4.2.2 Layering of fettuccine 4.2.3 Type of glue 4.2.4 Gluing method 4.2.5 Orientation of fettuccine 4.2.6 Joints analysis 5. Design Process 5.1 Bridge 1 5.1.1 Brief of the design 5.1.2 Testing 5.1.3 Conclusion 5.2 Bridge 2 5.2.1 Brief of the design 5.2.2 Testing 5.2.3 Conclusion 5.3 Bridge 3 5.3.1 Brief of the design 5.3.2 Testing 5.3.3 Conclusion 5.4 Bridge 4 5.4.1 Brief of the design 5.4.2 Testing 5.4.3 Conclusion
6. Final Model 6.1 Construction of joint 6.2 Construction of truss bridge 6.2.1 Basic Drawings 6.2.2 Cutting 6.2.3 Gluing (Layering) 6.2.4 Assembling 7. Final Test 7.1 Observation 7.2 Efficiency 8. Conclusion 9. References 10.Individual Case Study 10.1 Case Study 1 (Andrew Chee Kiong Chee Man Shing) 10.2 Case Study 2 (Meera Satheesh) 10.3 Case Study 3 (Lee Qin Ni) 10.4 Case Study 4 (Nicholas Lai Ken Hong) 10.5 Case Study 5 (Vendy William) 10.6 Conclusion
1. Introduction 1.1 General Purpose of Study This project aims to develop the understanding of tension and compressive strength of the construction materials and thus be able to evaluate, explore and improve as an overall the attributes of the construction materials. Besides that, this project is also a purpose to develop the understanding of force distribution in a truss by exploring and applying this understanding of this load distribution in a truss. During the span of this project, the ability of designing a truss bridge with a high aesthetical value but a minimal construction material is to be learnt. Moreover, through the process of designing fettuccine truss bridge, the exploration will be taken on different arrangements of member in the truss structure thus being able to evaluate and identify the tension and compressive members in this structure.
1.2 Report Preview In a group of 6, we were required to do a study of bridge trusses. As the first step, we were to find a precedent studies in which we can use as a clear reference for the design of our bridge. As starters, we planned to complete the necessary analysis to ensure we optimize the strength of the entire bridge in terms of the strength of the material in the different brands and experiment on each type of joint was also taken. After the completion of the design, the test models were then tested using water as how much water (Kg) it can with stand. Due to some failures, improvisations were taken and a newer bridge was built till the final one. The efficiency of the bridge was then calculated. Calculations regarding our individual case study was also included in the last few pages pf this report.
1.3 Restriction Material restriction: Fettucine Problems faced: 
Fettucine tends to be very brittle once kept in the open for a few hours. This challenged our design as this was one of the factors in which caused certain failures. Clear span restriction: 750mm Problems faced:

Having a clear span restriction gave us a challenge in calculating the ratio in which the bridge would be stable and have the capacity to carry the weight it itself and the additional weight. Weight restriction: 200g Problems faced:

The main problem we faced with this is the amount of fettucine needed to be used to ensure the strength is obtained but maintaining its weight.
1.4 Working Schedule Date 30/3/2015
Tasks Buy materials and preparation of the equipment Precedent studies analysis Fettuccine strength test Layering, glue test Joint test Construction of bridge 1 Testing of bridge 1 Construction of bridge 2 Testing of bridge 2 Construction of bridge 3 Testing of bridge 3 Construction of bridge 4 Testing of bridge 4 Construction of final bridge Final bridge testing Table 1.4.1
2. Methodology 2.1 Precedent Study 2.2 Construction of Fettuccine Truss Bridge There are 4 major phases in which are taken to complete this task. These phases are carefully thought out to ensure the best results were obtained. Phase 1: MATERIAL STRENGTH TESTING One of the main materials for this project is the fettuccine and the type of adhesive used. It is very important to test these materials properly to ensure they are capable of taking the load before skipping to the model making stage. The data showing the fettuccine strength results in the different circumstances and load is recorded under the analysis topic.
Phase 2: CHOOSING THE PROPER ADHESIVE In the second phase the proper adhesive was chosen. This choice is important as some adhesive may further increase the brittleness of the fettuccine, which may affect the strength of the entire structure later on. There are various types of glue with different characteristics that could have changed the strength of the fettuccine physically. These data and analysis is recorded in the analysis topic too.
Phase 3: MODEL MAKING Based on the study from our precedent studies as well as the analysis of the strength of the materials, we applied some improvements on the design of our truss bridge model. Having a triangle as a base of our design, we learnt in obtaining the perfect shape an AutoCad drawing is needed. Once that was complete, it was used as a template and the bridge was then joint.
Phase 4: MODEL TESTING & EVALUATION The finished model is tested by applying the load with a ribbon attached to the top of the bridge as to utilize the bridge as a whole and not only the base. The model is then tested and improved into the final designated model.
2.3 Structural Analysis The structural model was analyzed to show our understanding of the truss and how the load is transferred from one member to the other. The failed models are analyzed to discover the problem and it was then analyzed to be a reference for the next model. In the structural analysis, calculations and the direction of its load transfer are also shown in a diagrammatic form.
3. Precedent Study 3.1 Chambers Railroad Bridge
The Chambers Railroad Bridge is located in Oregon and it is the only covered bridge left in Oregon. It is a Howe Truss Bridge. Howe Truss design is suitable to be applied in Chambers Railroad Bridge for several reasons. 1) The members are modular 2) The angle castings and tension roads can be standardized 3) Compression members were of uniform length hence allowing prefabrication 4) The modest size of the structure allowed the construction of the bridge without needing to use large cranes. The idea behind this design is that the architect used materials where they could function at the most optimum. Steel or iron was used for the vertical tension members while wood was used for the angled compression members. These features not only enabled the bridge to be constructed in a short period of time, but also maintained the structure as one.
Joint Analysis
2 joint connection at bottom chord
1 joint connection at top chord
Load Transfer Analysis
4 members which are under tension
3 members which are under compression
5. Overall view of the bridge
3.2 Waddell "A" Truss Bridge
Waddell “A� Truss Bridge also known as Linn Branch Creek Bridge, it was built in 1898 for the Quincy, Omaha and Kansas City Railway and abandoned in 1939. The length of the largest span is 100.0 ft. and with the deck width is 16.0 ft.
However, in 1953, the bridge converted into a highway bridge and dismantled in 1980 to make room for Smithville Reservoir, but relocated to English Landing Park in Parkville in 1987. The bridge itself supported by big cylinder column and reinforced by lateral cross bracing between support columns. Not only for the support of the columns, were lateral crossbracing also used to reinforced upper chord.
Portal view on the Bridge
Support columns
Lateral cross bracing on upper chord
Lateral cross bracing between support columns
4. Equipment & Material Analysis 4.1 Materials Used The list below shows the main materials used in the construction and testing of the bridge.
San Remo fettuccine 1. OK brand 3-second super glue
2.
Baking Balance 3.
Blade
4.
Ribbon with ‘S’ Hook
5.
Empty pail and a bucket of water
6.
4.2 Material Strength Analysis 4.2.1 Type of fettuccine Having fettuccine as the main material for the construction of the bridge, its attribute is required to be studied in depth and tested before the model making process to ensure its strength is fully utilized as it should be. Each type of fettuccine found in the market has its own quality and value. These were carefully tested to ensure nothing goes wrong in the process of making the bridge. To build a strong bridge, it is crucial to know which brand of the fettuccine can be used and has the strongest strength to withstand the most loads. Below are the 3 types of fettuccine brands, in which was tested with a load hanging on one stick of fettuccine.
Fettuccine Brand
Weight Sustained (g)
Barilla Fettuccine
200
San Remo Fettuccine
165
Kimball Fettuccine
105
Shape of Fettuccine
Table 4.2.1 Fettuccine brands with description. From the table above, we found that the strongest fettucine is the Barilla brand, followed by the San Remo, then Kimball. Having have 2 of the strong fettuccine, we decided to do another test to determine the best out of the 2; Barilla & San Remo. Due to its expanded shape, the Barilla’s fettuccine has the most strength, but, having that shape; it has some disadvantages in terms of its banding with one another. This disadvantage may reduce its strength in general when we glue them together. On its own, it may be strong but when in contact with another, it has lost its ability to uphold that strength and capacity in holding a load.
Diagram 4.2.1: Results of 2 layers of Barilla fettuccine after a force is applied. The surface area in which has contact for the bonding is small. This causes the capacity of its bond strength is reduced, thus, causes it fall apart when a force is applied.
Diagram 4.2.2: Results of 2 layers of San Remo fettuccine after a force is applied. The surface area in which has contact for the bonding is larger compared to the Barilla fettuccine. This causes the capacity of its bond strength to be higher, thus, making it harder for it to break apart when force is applied. As a conclusion, we chose the San Remo brand as our choice due to its higher physical strength and larger capacity to stack in creating a stronger bond. Rather than its strength, it’ll ease our work on the construction of the truss bridge.
4.2.2 Type of glue Glue is considered the most important component in the construction of the truss bridge. This is what creates the bond in which joints and hold the whole structure together. To determine the best glue, we’ve done a few tests which is recorded in the table below. Constant Length = 60mm, clear span = 40mm, no. of layers = 2 Manipulated Adhesive, load [= water + 150g (container + hook + thread)] Responding Ability to withstand the load for 10 seconds *Remark: V=vertical, H=horizontal Water /g Adhesive 300 800 1300 V H V H V 3-seconds Bossils glue Dunlop x x PVC x x Super glue UHU x White glue x x 3s + Dunlop 3s + PVC 3s + UHU Bossils + Dunlop Bossils + PVC x Bossils + UHU
H x x x x x x x x x x x x
As a Conclusion, the 3-seconds glue is the most effective glue in creating the strongest bond. The combination of the 3-seconds glue and the Dunlop, PVC, or UHU was not appropriate for this task. White glue, being water-based, softens the fettuccine by a certain degree making the joints made weaker. Constant Length = 255mm, clear span = 110mm, no. of layers = 4, water = 500g Manipulated Adhesive *Remark: V= vertical, H= horizontal Adhesive V H 3s 3s + Dunlop x 3s + UHU x x
As a final conclusion, the 3-seconds glue was chosen as it performs well even in a longer clear span.
4.2.3 Gluing method Besides the choice of glue, the gluing method also helps in the strengthening of the bond. These tests below were conducted to ensure the best results are obtained without destructing or affecting the strength of the fettuccine.
Diagram 4.2.3(a): Glue is applied at only the ends of the fettuccine stick
Diagram 4.2.3(b): Glue is applied at the ends and the middle point of the fettuccine stick
Diagram 4.2.3(c): Glue is applied throughout the whole fettuccine stick
Type of Glue 3-seconds glue
Glue Layers Weight (g) Time (s) application 100 200 300 400 500 2 points 149.3 2 ~ 3 points 250.90 ~ Overall 285.12 Table 4.2.3 : Results when 3 different gluing methods was used and the load it can withstand.
As a conclusion, the fettuccine in which the glue was place all over, was proved to be the strongest, followed by the 3 interval points, and finally to the 2 interval points. In addition to this, the 2 and 3 interval points method which does not have glue throughout the whole fettucine allowed it to be more flexible. This showed a good balance between the compression and tension. In this case, the fettuccine was left to dry overnight, observation shows a series of irregular expanding and bending to occur, which eventually caused the fettuccine to be brittle. Finally, the method of gluing the entire fettuccine was chosen.
4.2.4 Layering of fettuccine Having chosen the proper gluing method, the numbers of layers are also important in this task as it shows the highest load it can take.
Constant Adhesive= 3-seconds, load (water= 500g), length = 255mm Manipulated No. of layers *Remark: V=vertical, H=horizontal Clear span /mm No. of layers 110 130 150 170 190 210 V H V H V H V H V H V H 2 x x x x x x x x x x X x 3 x x x x x X x 4 x x x 5 x x
230 V H x x x x x x
As a conclusion, the numbers of layers are needed to be increased as the clear span increased to ensure a constant load can be carried without the fettuccine breaking.
4.2.5 Orientation of fettuccine Another analysis we found that would help us for our bridge was the orientation of the fettuccine, to either horizontally or vertically. This would help us to determine which placement can be put at which position based on its strength.
Vertical Orientation
Horizontal Orientation
Diagram 4.2.5: Vertical and horizontal orientation of the fettuccine
Type of glue
Layers (No.)
Gluing Method
Weight Sustained (g) Horizontal Vertical 3-second glue 2 Entire 275.72 365.20 fettuccine 4 456.22 522.56 6 589.13 512.28 Table 4.2.5: Comparison between horizontal and vertical orientations with an increase in layers.
As a conclusion, as the layers increase, the strongest orientation will be vertical. Once the layers reach the limit of 6 layers, it is best to use the horizontal orientation. This result is due to the thickness the fettuccine obtains in comparison to its width. This ratio is the one that determines the ease at which the fettuccine breaks after a load acts on it.
4.2.6 Joints analysis Introduction Research on precedent studies of joints was conducted and 3 joints were chosen:
Butt Joint Mortise and Tenon Joint Lap Joint
These common joints are used in wood construction, however, it becomes suitable for this project, which does not require extra fixtures, and hence avoid any damage to the f e t t u c i n e .
Joint Assembly We used minimum 3 layers of fettucine to make the joints. 1. Butt Joint It is made by sticking the smaller surface area of the stick to one of the long surface area of the stick There is only 1 contact adhesive surface. 2. Mortise and Tenon Joint The middle layer of fettucine is extruded out by a distance equal to the width of the stick, thus creating the tenon at one side and the mortise at the other side. There are 5 contact adhesive surfaces.
3. Lap Joint One of the layer of fettucine on the sides is extruded out by a distance equal to the width of the fettucine stick, hence creating the laps at both ends. There are 3 contact adhesive surfaces.
Test We made a frame out of the fettucine sticks and the joints. For all data to be correctly recorded, we used the same glue, built the frame using the same stick dimensions. Equipment used:
3 Bottles Water Plastic bag Hook and Strap Weight Balance Stopwatch
Butt Joint
Mortise & Tenon Joint
Lap Joint
Data collected WEIGHT/g 500 1100 1500 2000 2400
BUTT
Time / s MORTISE AND TENON
LAP
X (2.6) X X X
X (3.93) X
X (1)
Analysis
Butt joint lasted for 2.6 seconds and failed at 1100 grams. Butt joint is tested to be the weakest among the 3 joints, since it consists of only 1 contact adhesive surface, hence the small area where the glue was applied was not strong enough to withstand the weight.
No damage occurred on the fettucine stick. Only the glue joint snapped.
Surprisingly, the mortise and tenon joint is the second weakest or strongest of the 3. Theoretically, having 5 contact adhesive surfaces, which is more than the lap joint, the joint should have provided the strongest joint. However, referring to the picture, the glue did not snap. Instead the extruded stick broke. The joint broke similarly when using shear force. Because of the large amount of contact adhesive surfaces, there were 2 forces acting on the extruded stick: Compression and tensile strength.
The lap joint is considered the strongest. We notice the broken part is similar to the mortise and tenon joint. However, because there are less forces acting on the extruded part, hence being able to support heavier loads.
Conclusion The mortise and tenon joint and the lap joint provided much better result and almost identical. Using both joints is suitable to add in places with require opposing compressive forces. The butt joint can be used but in places which does not require much strength.
5. Design Process 5.1 Bridge 1 5.1.1 Brief of the design There’s a lot of different types of trusses. After studying all the trusses that we know and also from our precedent studies, we tried to figure out which one is the best truss using some calculation that has equivalent distributed loads. From our analysis, we found that Howe truss has equivalent distribution of loads. We then tried to create a new design from fettucine that can hold certain loads. According to our research, triangle is considered the strongest polygon that cannot be “squished” due to the angles which are constant. This induces it to be very good in compression and tension so the structure can handle huge loadings before failure. If other shapes, such as rectangles, were used, the angles could twist, allowing movement and collapsing to happen at a much lower load.
Figure 5.1.1(a): Comparison of the distribution of forces in a rectangle and a triangle
5.1.2 Testing The bridge can hold around 1.5kg with the weight 200grams. The bridge snapped in 3seconds and from here we started analysing the bridge and it was concluded that it was overweight and very weak. Having had many unwanted fettuccine which didn’t help in supporting the loads but rather just plainly adding to the weight was one of the few reasons for the snapping. Some other reasons the bridge snapped are due to poor workmanship, wrong placement of the bracing and layering.
DENSITY OF LOADS DISTRIBUTED
Conclusion After identifying the reason behind the snapping of the bridge, we came into a conclusion whereby good workmanship will help to hold more weight. At this stage we has a clear understanding that the positioning of the bracing was also very important.
Figure 5.1.2(a): Unnecessary Fettucine
Figure 5.1.2(b): Wrong placement of bracing and layering
5.2 Bridge 2 5.2.1 Brief of the design Prior to the testing of the previous bridge, we have analysed the weak parts, mistakes and came to some improvements to the design of the bridge. For pre design, we did a smaller scale model with a span of 400 mm. As a result of the testing of the smaller model, we scaled it up to the full span of 800 mm.
The top chord of the bridge was reimagined. The continuous long fettucine stick was replaced by several individual fettucine members. The design idea was that a short multi layered brace would be compressively stronger than a longer one. Thus the strength of the structure would mostly depend on the joint, since each short brace would be individually strong. Each horizontal members were joined to a triangular profile, strengthened by another triangular profile inside. Cross bracings were added to strengthen the base. We designed specifically a support, where we would hang the load.
Figure 5.2.1(a): From top left to bottom right: Front, side elevation, load support, triangular profile
5.2.2 Testing Pre-design At around 2.5kg, the load support broke after 10 seconds.
Figure 5.2.2(a): Failure point at the load support Full scale
Figure 5.2.2(b): Testing the full scale model The load support was redesigned with a weight of 210 g. With a load of 2.7 kg, the bridge snapped within 3 seconds. The failure occurred at both ends of the bridge where the structure was resting on the table. Consequently the whole bridge broke from the impact on the floor.
Figure 5.2.2(c): Breaking point at both ends
5.2.3 Conclusion The design was not efficient. Testing revealed several weak points in the design. The triangular profile proved to be strong, however improvements had to be considered on the rest of the structure.
5.3 Bridge 3 5.3.1 Brief of the design Prior to the testing of the previous bridge, we have analysed the weak parts, mistakes and came to some improvements to the design of the bridge. We kept the initial idea of bridge 3 and proceeded on reinforcing the base and load support.
Underneath the triangular profiles, we added two additional continuous beams, in order to have greater stability and increase the tensile strength. However we decreased the number of layers of fettucine on the bracings and upper beam, so that the bridge would be under the weight limit of 200 g. The internal triangles have been removed, also to take out some excess weight from the bridge. The load support was changed as we planned to distribute the load along a greater span.
Figure 5.3.1(a) From top left to bottom right: Front, side elevation, reinforced base, triangular profile
5.3.2 Testing The structure weighed 230 g and was able to support a load of 2.9 kg until failure.
Figure 5.3.2(a): Triangular profile broke Due to the removal of several layers of fettucine in order to respect the limit of weight of the bridge, the triangular profile was weakened. It collapsed at one end of the bridge at the part, as it is shown in the figure 5.3.2(a).
5.3.3 Conclusion
After trying several solutions to solve out the strength and weight issue, it has resulted into poor efficiency. Hence one of the possible alternatives was to change the design, but still keeping the initial idea. Thus resulting into Bridge 4.
5.4 Bridge 4 5.4.1 Brief of the design
Figure 5.4.1 (a) From top left to bottom right: Side elevation, bird’s eye view of the bridge, connections at the top of the bridge, connection at the bottom of the bridge
As we proceed to design and build the prototype of bridge 3, we came out with a slightly modified idea and design of another bridge. Due to the lack of time, we designed and build the prototype of bridge 4 at the same time as building bridge 3. The reason behind making a second different prototype to be tested out is because we noticed that in previous prototypes, the triangular components doesn’t connect with each other well, resulting a heavy and weak bridge. As both have slightly different method of construction and design, we decided to test both of the prototype and determine which bridge is the strongest. The concept of a triangular form and the type of joints maintained with the following adjustments:
Figure 5.4.1 (b) Drawing of the joining of the triangular components
Figure 5.4.1 (b) shows the method of the joining of the triangular components for the previous bridge prototypes. The idea of this construction method is to make the triangular components followed by adding long horizontal members to support the triangular members from the inside. In the prototype bridge 4, instead of following this method and idea, we make the whole bridge as a one continuous triangle component.
Figure 5.4.1 (c) Idea of a triangular bridge as a single component which shows the idea of making the bridge as a single component instead of joining several triangular components together via a long horizontal member. This will allow forces to be transferred more efficiently.
Figure 5.4.1 (d) A faรงade of the bridge which shows one faรงade of the bridge constructed. This faรงade will be duplicated to produce two similar faรงade to form the two sides of the bridge.
Figure 5.4.1 (e) Method of forming a triangular bridge
The two faรงades are then joined together at the top with a wide opened base to form a triangular bridge. The base of the bridge is supported with horizontal members to complete the triangular bridge form.
Figure 5.4.1 (f) Base of bridge 4
5.4.2 Testing The structure weighed 225 g and was able to support a load of 3.0 kg until failure.
Figure 5.4.2 (a) Diagonal member
The diagonal members of the bridge are too weak and they were the first members to bend and eventually snapped. This is due to: 1. It only consists of one layer of fettuccine. 2. The orientation and placement of the diagonal member is incorrect as they failed to support the upper part of the bridge.
5.4.3 Conclusion After testing and conducted the efficiency calculation, it has resulted a slightly better result compared to bridge 3. Hence the idea of this bridge 4 of making a bridge into a single triangular component is used for the final bridge design. Changes that were implemented into the final design to be improved from this bridge 4 prototype were: 1. The orientation of the diagonal supporting member. 2. The positioning of the diagonal supporting member. 3. Increase number of layering of the diagonal supporting member. 4. Improve workmanship. 5. Load to be hung on the top of the bridge instead of at the base of the bridge.
Figure 5.4.3 (a) position and orientation of original diagonal member.
Figure 5.4.3 (b) position and orientation of the diagonal members to be improved to.
6. Final Model & Construction Process (Nic + Meera) 6.1Final Model
Diagram 6.1 (a); The model of the final design
SIDE ELEVATION
TOP ELEVATION
SECTION
ISOMETRIC Diagram 6.1 (b); The basic drawings of the final design
EXPLODED AXONOMETRIC
EXPLODED SIDE SECTION
6.2 Construction Process Before constructing the truss bridge, we’ll have to determine the types of joints that were used in constructing the bridge. They type of joint used in specific parts of the bridge is crucial to utilize the strength of the whole bridge.
6.2.1 Construction of joints 6.2.1(a) Lap Joint The lap joint was used in the major parts of the structure due to its great strength. The steps in creating this joint are quite simple and allow a larger surface area to be in contact with each other, thus making the joint harder to fall apart. Steps:
1.
2. 2 of the fettuccine from A and B were glued together
The materials were first prepared
4.
3.
The 3rd fettuccine was then glued to the first 2, but slightly translated (one inwards and one outwards) from the ends like the above diagram.
As a result, 2 pairs of the set above will be obtained
Glue the 2 side firmly overlapping one another. Thus, the lap joint is formed. This joint was used in the crucial parts of the bridge: such as for the base and top parts of the truss.
5.
6.2.1(b) Tenon & Mortise Joint Being the next strongest joint, the tenon & mortise joint were used as part of the averagely important part in the structure. This joint may be easier to fall apart due to the single layer which is clamped by 2 more fettuccines. This joint is more complicated to make although its strength may not be as strong as the lap joint.
Steps:
2.
1. The materials were first prepared
2 of the fettuccine from A and B were glued together but slightly translated (one inwards and one outwards) from the ends.
4.
3. The 3rd fettuccine was then glued to the first 2, once again slightly translated (one inwards and one outwards) from the ends like the diagram above.
As a result, 2 pairs of the set above will be obtained
5.
The 2 fettuccine strips were then firmly glued together to form the tenon and mortise joint. This joint was used for the support trusses in our final model
6.2.1(c) Butt Joint The butt joint is by far the easiest joint to be constructed but yet the easiest to fall apart. This joint has only one surface in which is contact with the other fettuccine making it very fragile.
2.
1. The materials were first prepared
4.
All the 3 fettuccine from A and B were glued together.
3. The 2 pairs of fettuccine was then firmly glued together to form a butt joint. Due to its low strength, this joint was used only as the secondary support for the truss. Besides that, it was also used as a tool to ensure the crosssectional shape is retained even during the testing.
As a result, 2 pairs of the set above will be obtained.
6.2.2 Construction of truss bridge 6.2.2(a) Cutting The fettucine was first separated according to its usability and its length. The good ones are the once which are least bent. The ends of these fettuccine were then trimmed and sand papered. The longer ones are then used for the base while the smaller ones were then further cut according to the sizes which were needed for the major supports; the minor supports a well as the base support member. 6.2.2(b) Gluing The next step is to glue all the needed parts together. The base was first glued together using the lapping method to ensure full coverage in the joint area, and thus making the bridge solid from the start. The smaller trusses were then glued together in 3, along with the minor trusses as well as the base support. 6.2.2(c) Assembling Steps :
1.
2.
The base of the bridge was assembled first using the overlapping method.
Secondly, the major trusses were placed in firmly
3.
After that, the top of the truss was then glued together alongside the major trusses to ensure the whole one side of the structure is firmly attached to one another. The gaps in which are left are then filled in and another layer is placed on it.
4.
Steps 1 to 3 are then repeated to create another truss identical to the one before.
5.
After preparing the 2 main trusses, the support trusses are then used and cut in an angle to ensure the surface area is maximized for the gluing process.
6.
Ones the 2 sides are completed, the trusses are then placed together to be joint at the top.
7.
Before gluing them together, at least 3 base support members were glued at the top of the base to ensure constant gap between the 2 bases.
8.
9.
Later, another piece of fettucine was used as an extra member to help in gluing the two trusses together. This step is taken to ensure there is enough surface area in which allows the 2 trusses to firmly be glued to each other.
The rest of the base support was added and the bridge was left to dry completely.
7. Final Test From the previous bridge 3, to strengthen the upper chord, we changed the connections from separated individual connections to a continuous strip connection. However, the bottom chords remained as our load is received mainly by the upper chords. Hence, if we continue to further strengthen the bottom chords, it would add unnecessary weight to the bridge. Also, instead of having individual separated triangles, we changed the bridge design to 2 symmetrical trusses which meets at the top, as shown in the section drawing below.
7.1 Observation Members highlighted green are under compression while members highlighted blue are in tension. Load is acting downwards by the pulling force from the bucket filled with water.
Our bridge weighed 197 grams and snapped at withstanding 9141 grams of load.
Based on our observations: 1. It can be observed that the bracings at both ends were weaker as these bracings were deflected from withstanding the load applied. 2. Our bridge snapped at the diagonal truss bracings. 3. The top chords were not strong enough hence they had deflection prior to breaking.
Figure 7.1.1. Closer views of snapped members
From our observations: 1. In order to strengthen the weak bracings at both ends, we could design ‘X’ bracings. ‘X’ bracings are stronger in receiving compression compared to diagonal bracings. 2. Layers of fettuccine can be added to further increase the strength of the top chords. However, this will exceed the maximum weight allowed, 200 grams.
7.2 Efficiency of bridge Based on the formula:
8. Conclusion As a conclusion, this bridge has a result which is best compared to all the prototype bridges. Hence making a bridge into a single triangular component is considered the best method to ensure the maximum utilization of the strength in which the fettuccine can withstand. Changes that were implemented into the final design to be improved from the 4 prototype bridges were: 1. The orientation of the diagonal supporting member. 2. The positioning of the diagonal supporting member. 3. Increase number of layering of the diagonal supporting member. 4. Improve workmanship. 5. Load to be hung on the top of the bridge instead of at the base of the bridge.
11.6 Conclusion As a final conclusion, case study 5 has the best truss according to our calculations and analysis. This is due to the higher distribution of the weight rather than having a major and drastic difference in its value. The strength of the 5 cases can be said as; case study 5 to have the best while case study 1 has the least. The ordering of the trusses are from 5 to 1 in order; which is from the best to the worst.