TABLE OF CONTENT Page Number 1.0 Introduction 1.1 General purpose of project
1.2 Report overview
3.0 Aim and Objective
4.0 Precedent Study 4.1 History and function 4.2 Truss Analysis
5.0 Equipment and Materials 5.1 Equipment 5.2 Materials
6.0 Experimenting Progress 6.1 Timeline 6.2 Development of truss bridge
7.0 Final model testing 7.1 Design of truss
7.2 Jointing methods
7.3 Load analysis 7.4 Final testing of truss bridge
1.0 Introduction 1.1 General purpose of project In a group of 5, we were assigned to design and build a truss bridge using a normal household good â€“ fettuccine. With a minimum clear span of 750mm and the weight must not exceed 200g, the fettuccine has to withstand a higher load to achieve better efficiency. It also trains students to design a perfect truss bridge which fulfill the criteria of high aesthetic level and utilizes minimal construction material. Moreover, this assignment must be complemented by a precedent study of our choice. Through this project, we are able to explore truss members in different arrangement and understanding its strength by applying knowledge in load distribution of a truss system. We are also able to understand and apply the knowledge on calculating the reaction force, internal force and determine the force distribution in a truss. By doing so, we are able to identify which member in the truss system needs to be strengthened in terms of its tension or compression.
1.2 Report Overview The report starts off with a precedent study for us to gain insights on how the design of a truss bridge affects its strength to withstand loads and its construction methods. The report contains methodology and various truss bridge designs which were documented and analyzed in every attempt to test its efficiency, prior to conclude on a final design. Load testing on different bridges were carried out very carefully and documented in all kind of methods such as manual writing, taking photos and video recording. A set of analysis regarding the strength of the bridge structure and its reason of failure had been done. Suggestions on how the bridge can be improved are also included in the report. The individual case studies are also attached at the end of the report to show our understanding of truss bridge constructions.
2.0 Methodology In a group of five, students were assigned to design and build a truss bridge using fettuccine. Firstly, precedent study of Taylor-Southgate Bridge had been conducted to gain an insight on how a truss design could affect the structural strength and its construction methods. To achieve a higher efficiency of fettuccine bridge, the strength of fettuccine was being tested to examine its ability of load sustaining. Moreover, various types of glues were tested by applying a point load at the center of a threelayer fettuccine stick. Secondly, four designs of truss bridge had been constructed to test on its efficiency in load distribution and withstanding higher loads. Each type of the fettuccine bridge was not in a smaller scale, instead, all bridges are constructed in real sizes to test on the efficiency more precisely. Warren Bridge was chosen to be incorporated in the final design. Thirdly, model making and testing of fettuccine bridge are the primary steps throughout this project. A set of AutoCAD drawings were generated before model making to attain a better measurement. Referring to the dimension provided in the drawings, we can minimize the mistakes in calculation during model making that might lead to inefficiency. The main structure of fettuccine bridge was constructed first. Then, intermediate members at different positions of the bridge were installed to connect the gaps between the main structures. Fourthly, load testing was carried out upon the completion of each fettuccine bridge. A pail, S-hook and 500ml-water bottles served as the equipment for load testing. The Shook were to connect with the centre point of the fettuccine bridge and the pail filled with water from the bottles acted as loads. Lastly, a thorough analysis of the fettuccine bridge was executed to examine its strength and its reason of failure. Various ways of improvement were suggested to improvise in the next model making so as to acquire a higher efficiency fettuccine bridge.
3.0 Aim and Objective This project aims to develop studentsâ€™ understanding on force distribution in a truss and every design and construction method would affect its efficiency in withstanding loads. Proper planning, conducting precedent studies and carrying out load testing prior to get a final design of fettuccine bridge helps students to understand the compression and tension forces in a bridge. Through exploring different arrangement of trusses, students will be able to identify the type of truss bridge which best suit in accordance to the properties of material. Students are also exposed to different methods of placing the elements and joints construction, based on type of forces applied to the members. Lastly, this project also trains students to design a perfect truss bridge which fulfill the criteria of high aesthetic level and utilizes minimal construction material.
4.0 Precedent Study 4.1 History & Function The Taylor-Southgate Bridge connects Newport, Kentucky to Cincinnati, Ohio and spans the Ohio River. It carries US 27 and replaced the 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. Federal funding was secured in 1986 by former congressman Gene Snyder, a Jefferson County Republican. However, funding and location wrangling between the Kentucky Transportation Cabinet and the City of Cincinnati curtailed the project until 1991. At topic was funding contributions from the city of Cincinnati. In early 1990, the states of Ohio and Kentucky had requested $10 million from the city towards the $56 million project, although the city had refused to expend on the bridge. The strong disagreement from the city caused officials of Ohio, which had committed $10 million to the bridge, to threaten to switch the stateâ€™s contribution to construct a bridge between Maysville, Kentucky and Aberdeen, Ohio. Kentucky had committed $7 million towards the bridge, while the federal government had committed $28.5 million. Another lingering issue was a warehouse along the Ohio River on the Cincinnati side that created design problems for the bridge project. The property, Cincinnati Commercial Warehouse, was refrigerated and demolishing it would be costly. In 1991 the City council approved to spend $25,000 to cover staff work on designs and right-of-way review, and agreed to spend $4 million on the bridge but not until 1994. Other money for the project included $8.5 million from Kentucky, $12.9 million from Ohio, $2 million from Hamilton County, Ohio, and $28.5 million from the federal government. The $56 million bridge was projected to start in 1996, but was completed in 1995. The crossing was named after James Taylor, Jr. and Richard Southgate, two early settlers of Newport.
4.2 Truss System Taylor-Southgate Bridge is a truss girder bridge which uses Warren truss that has vertical members in every designated span to distribute loads.
The Warren Truss was patented by James Warren in 1848. It has been around a while. It is one of the most popular bridge designs and examples of it can be found everywhere in the world. One of them is none other than Taylor-Southgate Bridge. The Warren Truss uses equilateral triangles to spread out the loads on the bridge. This is opposed to the Neville Truss which used isosceles triangles. The equilateral triangles minimize the forces to only compression and tension. Interestingly, as a load such as a car or train moves across the bridge, sometimes the force of a member switches from compression to tension. This happens especially to the members near the center of the bridge.
Exterior and Interior Views of the Bridge
Exterior and Interior Views of the Bridge
Span 560m across Ohio River, it was designed to relieve traffic from the adjacent Roebling Suspension Bridge.
The truss members constructed at the outer part of the bridge uses thicker steel structures.
The truss members were constructed equivalent at all sides and it creates a smooth rhythm throughout the whole span. 8|Page
5.0 Equipment and Materials 5.1 Equipment 1) Pen knife Pen knife was used in the model making process to cut the fettuccine strips.
2) Camera Camera was used to take pictures to document the working progress and record videos during load testing.
Pail was used during load testing to hold the loads â€“ water.
4) S-hook S-hook served as the connector of Fettuccine Bridge and the load during load testing. It managed to stabilize the loads very efficiently to minimize any unwanted forces transferred to the bridge.
5) Sandpaper Sand paper was used to during model making to correct the mistakes done in gluing.
6) 500ml water bottle 500ml water bottle was used during load testing as loads. It was very easy to handle and helped to achieve the waiting time of 5 seconds after every 500g was applied to the fettuccine bridge
7) Weighing Machine
Weighing machine was used throughout the whole model making process and load testing to determine the weight of the Fettuccine Bridge and loads.
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5.2 Materials Fettuccine
Fettuccine was the main material used to construct the truss bridge. Research and analysis on its strength were conducted as shown below. Testing of the strength of fettuccine
Layers of members 1 layer 2 layer 3 layer 4 layer 5 layer (I-beam)
Length of fettuccine (cm) 26 26 26 26 26
Clear span (cm) 15 15 15 15 15
Load sustained, Horizontal facing (g)
Load sustained, Vertical facing (g)
400 500 800 1300 -
200 400 800 1400 1820
Table 5.2.1: The test result for the fettuccine strength
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Super glue was used in the final model as it has the highest strength in connecting joints and withstanding loads, though it solidifies and dries up in a slower time.
Throughout the whole model making process, 3-second glue was used to connect all the truss members together. It dries up fast and has adequately good strength in withstanding loads.
Testing of the adhesive strength Types of adhesive Super glue (Elephant) 3 second glue (V-tech)
Analysis - Slower solidify time duration (10 seconds) - Highest bond strength & efficiency - Strength of the bond between connections increases after a certain period - Fastest solidify time duration (3-5 seconds) - High efficiency - High connection bond strength - Gets brittle faster and has higher tendency to crack after a certain period - Slowest solidify time duration (30 seconds) - Average efficiency - Average connection bond strength
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6.0 Experimenting Progress 6.1 Timeline
Figure 6.1.1: The working progress timeline
Working schedule 20th
Date September 2014
Work progress Testing of strength of fettuccine by using 1, 2,3 and 4 layer and using I-beam design
21st September 2014
Testing different way of jointing the fettuccine and using different kind of adhesive to test the strength
26th September 2014
Discussing and making decision on which truss design to construct
27th September 2014
Making the second and third model and proceeded with testing the first, second and third model
29th September 2014
Making the fourth model and testing the fourth model
1st October 2014
Final truss bridge model making session. Refining the bridge model Final submission and load testing of Fettuccine bridge
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6.2 Development of tested truss bridges Model Testing 1
Analysis This is our first model built for testing. The idea structure is basically following the classic warren truss bridge. This is because we should like to test how strong is this kind of truss bridge can sustain the load. Beside that we design the bridge dimension into a cube shape in every part of the beam column. Clear span Weight of bridge Efficiency
= 750mm = 180g = 4.86 %
Total length = 940mm Total load withstand = 935g
Analysis After testing the model, the whole bridge structure is still remaining good condition, only the supporting component part broke down. So we decide to change the supporting component part to an I-beam structure and having the load test on the same model again. We found out that the I-beam structure help a lot on the model efficiency. Clear span Weight of bridge Efficiency
= 750mm = 180g = 140.8 %
Total length = 940mm Total load withstand = 5.035kg
In this testing model, the failure component is the beam and also the horizontal joint that connect the two bottom beam. After the study, we find out that it might be the bridge too long and also the craftsmanship causing it failed. Workmanship is one of the reasons that cause failure because the members connecting two trusses aren't perfectly installed.
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Model Testing 2
Analysis This is the second model of warren bridge. In this model we have make two changes. The first changing part is the length of the bridge. We shorten up the bridge to 840mm. The second change is we design all columns slot into the beam layers. As a result the beams are holding the columns together. Clear span Weight of bridge Efficiency
= 750mm Total length = 165g Total load withstand = (load)2/weight of bridge = 4.0352/0.165 = 98.67 %
= 850mm = 4.035kg
In this model, the end part of the bridge is break into two pieces. We also find out several problems that we were faced and need to be solving which are: 1. Making sure the breaking point location of the fettuccine is evenly spread out for the base 2. Strengthen the vertical joints 3. Extending the end of the base 4. Reduce the weight of the bridge by reducing the horizontal joints to one layer
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Model Testing 3
Analysis This is the third model of warren bridge. On the previous model, we found out that the slot in column method is not efficient and helpful. So we refer back from the model testing 1 and shorten the whole bridge length into 910mm. Besides that, to lower down the weight of the bridge, we reduce the number of fettuccines on the top part of the beam. So, we are using 3 layers of fettuccine on the top beam and 4 layers of fettuccine on bottom beam. Clear span Total length Weight of bridge Total load withstand Efficiency
= 750mm = 910mm = 170g = 3kg = (load) 2/weight of bridge = 32/0.17 = 52.94 %
In this model, fewer problems are found. The failure occurs at the middle part of the top chord, because the members are in compression and the highest load bearing members are thin.
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Model Testing 4
Analysis This is the fourth testing model. We have made a major change which is using the Ibeam structure into our beam. This is because during the previous model, we studied that all the broken parts are on the beam. The bridge starts to collapse due to the strength of the beam. So we decide to use the I-beam which it contains of 6 layers of fettuccines although it will increase the weight of the entire bridge. Clear span = 750mm Total length = 910mm Weight of bridge = 200g Total load withstand = 4.035kg Efficiency = (load)2/weight of bridge = 4.0352/0.2 = 81.24 % Problem identification
For this model at first, we assume that the failure will be fail in structure and it may occur on the middle member which under compression force since fettuccine is poor in compression force. However, it shows that the frame is still intact, just the minor members failed upon craftsmanship and we also find out that I-beam was not so helpful in the whole bridge structure.
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7.0 Final Model Testing 7.1 Design of truss
Figure 7.1.1: Warren truss design
For the final model testing, we decided on using the Warren truss design as it reaches the highest efficiency after several times of model testing. The Warren truss design is one of the common truss designs that is used in most bridges and based on our precedent studies. The truss is modified a little bit to enhance the bridge design in terms of efficiency.
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7.1.1 Amendments of dimension
The distance between each vertical members are always constant at 80mm whereas the base length of the bridge was changed from 80mm to 55mm. The length of the base is increased in order to make sure the vertical member of the last chord rest inside the tables accurately. This is to prevent failure to the horizontal member and also to prevent the vertical member to be hanging without any base support.
Figure 7.1.2: Model testing version of Fettuccine Bridge. The last vertical member is not resting at the edge of the table.
Figure 7.1.3: Final model version of Fettuccine Bridge. The last vertical member is resting at the edge of the table.
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7.1.2 Making of the final model
The bottom and was sticked together in place first. The fettuccine is cut and stick according to the dimension and each of the horizontal components are 4 layers in total.
After constructing the horizontal components, the vertical members are erected to connect the top chord and bottom chord. These vertical members act as vertical posts for the fettuccine bridge to resist tensile strength that was created by point load.
The third step is to add the diagonal members at gaps in between the vertical. The horizontal members functioned as bracing to truss which is able to resist shear force.
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The next step is to connect the remaining members into place so that the bridge will be stabilized. After constructing all the members, the model was left to dry for 2-3hours before the final testing.
Lastly, the steps are repeated to create the other facing of the bridge. Both vertical facing is connected using a series of members of 80mm in length. The members are connected to the bottom chords and top chords of both frames. The distance of each member is 80mm.
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Figure 7.1.4: The fettuccine are all cut according to the length of the drawings.
Figure 7.1.5: The diagonal members are connected to the vertical members.
Figure 7.1.6: The two facing of the bridge are connected using a series of members.
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7.2 Jointing Methods 1. Beam
The horizontal beams of the final model are made up of 4 layers. In order to get the required length of 640mm for the top beam and 860mm for the bottom beam, calculations were made to ensure the splits of every fettuccine does not meet alternatively. Precise measurements and good workmanship of fettuccines allow the ends to fit perfectly when connecting them into a straight and long single beam. This will strengthen the stability of the beam and allow the adhesive to bond them seamlessly. Based on the analysis done (refer to table 5.2.1), the beams are stronger when it is connected vertically. Besides, with a larger surface area facing outwards, it creates a stronger jointing bonds between the beam and other bridge components.
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2. Diagonal beams connection
The ends of the diagonal beams were cut at an angle to allow an accurate beam-to-beam connection. These angles were calculated precisely to ensure even distribution of load when forces act on it. A direct and precise contact of the end of the beam surfaces also allow the adhesive to bond them strongly, thus creates a durable joints. 3. Vertical member
The vertical members are made out of 2 layers of fettuccine. It is connected directly onto the surface of the horizontal beam at an interval of 80mm from using super glue as the adhesive. These vertical members are connected at the split of the beam to further strengthen the beam.
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4. Diagonal member (bracing)
The diagonal members act as the bracing of the truss bridge structure. The edges of these members were calculated and cut at an angle to make sure that it fits perfectly in the spaces between the vertical members and beam. By having an accurate workmanship, it will also increase the efficiency of the bridge as it reduces the weight of the bridge by having the excess part of the component removed. 5. Horizontal members
Different layers of fettuccine were used as the horizontal members strengthening the connection reinforcement between the two bridge frames. This member is placed with horizontal facing, which has a larger surface area to ease the procedure of jointing. Only one layer of fettuccine was used as the top horizontal member, as the member does not resist much load other than tensile force. This layer of fettuccine is connected directly on top of the beam using super glue. For the bottom horizontal member, 2 layers of fettuccine were used to further reduce tensile force. It is attach directly on top of the bottom beam, behind the vertical member using super glue as well. This helps distribute loads more effectively.
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6. Centre component
The centre components of the bridge consist of different number of fettuccine layers connected to one another as it is the part that bears the most weight. At this centre point, the vertical member consists of 3 layers, whereas the rest has only 2 layers. The top horizontal member which holds the two frame component has 2 layers of fettuccine compared to the other top horizontal member that has only one layer. Lastly, the most important component of this bridge structure would be the horizontal I-beams that connect the two frames. This I-beam consists of 5 layers â€“ 3 in between and one each on top and the bottom. This I-beam serves as the main component to hold the testing loads. Through the few experiments done (refer to table???), using I-beam as the middle component gives a stronger advantage in withstanding more loads before the structure collapse. I-beam has been chosen to be used only in the centre due to its heavy weight which may bring down the efficiency of the bridge. However, it is more than sufficient to ensure these loads will be distributed evenly through this I-beam, to both sides of the bridge frames, vertical members and bracings of the structure.
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7.3 Load Analysis To ensure the bridge can withstand a high efficiency, we calculated the tension and compression members in our truss bridge design as shown in figure 7.1.7.
Figure 7.3.1: The tension and compression force in the members. As the strength of the fettuccine is higher under tension force and lower under compression force, the upper and bottom chord are strengthened using 4 layers of fettuccine each. Both bottom and upper chord have the equal layer of fettuccine to ensure that the force transferred will be equal along. The vertical members are strengthened with 2 layers each and only 3 layers at the middle of the bridge as the load force will be more at the middle of the bridge. The diagonal members are all in 2 layers to strengthen under compression force.
Figure 7.3.2: The layers of Fettuccine used in each structural member
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7.4 Final testing of truss bridge
Clear span = 750mm
Total length = 860mm
Weight of bridge = 177g
During the final testing of the bridge, the only part of the bridge that broke was the middle component that holds the load. The bridge manages to withstand 6.140kg before it broke. After the testing, we analyze the problem that cause the bridge to fall which we assumed it may be due to the force from the load that cause the I-beam to break into half. The other members of the bridge structure were stable and in very good condition even though it broke. This is proven that the craftsmanship during the model making process did not cause any problem.
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7.4.1 Efficiency of bridge From the formula given, the efficiency of the bridge is calculated as square of maximum load applied on the bridge divide by the total weight of the bridge itself. In order to achieve high efficiency, the weight of the bridge should be as light as possible and able to carry load as much as possible. After finishing the load testing test, we calculated the efficiency of the bridge.
Total load withstand = 6.140kg Efficiency = (load)Â˛/weight of bridge = 6.140Â˛/0.177 = 213 % From the result we gained from the model testing, we succeed in achieving the efficiency of 213% which proven that the bridge is able to withstand the load without damaging the main structure. The bridge was still in very good condition where all the main components did not break. There might still be slight mistakes in terms of the workmanship and also how the members are connected together. If there was more reinforcement added to the center point of the bridge where the load is hanging, the bridge might be able to withstand more loads. In addition, the final model are finish constructing one hour before the load testing to ensure the bridge does not get affected by the chemical effect of the super glue that will cause the fettuccine to be brittle.
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We had constructed a total of 5 fettuccine bridges and experimented on its efficiency in withstanding loads. The precedent study we chose to study on is Taylor-Southgate Bridge which uses Warren truss in its truss arrangement. We had also concluded on using Warren truss as it is one of the simplest yet strong designs. What made the Warren truss unique is that it uses equilateral triangles for load distribution. The equilateral triangles minimize the forces to only compression and tension. To our astonishment, when load is applied to the bridge, sometimes the forces of components switch from compression to tension, especially those near to the centre of the bridge, to increase its efficiency in load distribution. In our final model testing, we achieved the highest efficiency compared to the previous 4 models we have done. Our fettuccine bridge achieved an efficiency of 213%, withstanding a total load of 6.140kg and its weight is only 177g. This project has made us understand load distribution in a structure deeper, compared to the previous semester, as we are able to calculate the type of force applying in each structure member. It is very important to understand how each member works together as a whole in a structural system in attaining a higher efficiency. Other than understanding how each member works, there were a few other factors we took into consideration very carefully from the construction of bridge until the end stage of load testing. During the design stage, we pushed ourselves to use as little materials as possible and increase its durability to achieve higher efficiency. We also realized the importance of proper planning, in terms of work delegation and the time interval between completion of bridge and load testing. It is due to the efficiency of completing the bridge on time and giving an adequate time for the adhesives to dry out and maintain its strength until load testing. We have strived to achieve highest accuracy in the measurement of each truss member by generating AutoCAD drawing and printing it out to refer. Besides, we also strived to achieve highest workmanship by working on the bridge carefully and steadily. In conclusion, it has been a great experience working on this project. Using normal household goods to construct a bridge and gaining so much knowledge after that have amazed us how strong a structure can be if it is properly designed and constructed. As an architecture student, we will be the leader in the construction industry in future, we need to think critically and pay attention to details so that a structure can function efficiently without failure for the safety and wellbeing of the people.
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References Boon, G. (2011, January 4). Warren Truss. Retrieved October 3, 2014, from Garretts Bridges: http://www.garrettsbridges.com/design/warren-truss/ Ching, F. D. (2008). Building Construction Illustrated Fourth Edition. Canada: John Wiley & Sons Inc. Unknown. (2000-2014). Taylor-Southgate Bridge (US 27). Retrieved October 3, 2014, from Bridges & Tunnels: http://bridgestunnels.com/bridges/ohio-river/taylor-southgatebridge-us-27/ Unknown. (2002-2014). Taylor-Southgate Bridge. Retrieved October 3, 2014, from Bridge Hunter: http://bridgehunter.com/oh/hamilton/taylor-southgate/ Unknown. (2010, June 20). Taylor-Southgate Bridge. Retrieved October 3, 2014, from Cincinnati: http://www.cincinnati-transit.net/taylorsg.html
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