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BRIDGE BUILDING Bridge Building Problem-Solving Method Design Harden, Mona, Icey, Jonathan, Khan May.16.2016 BRIDGE BUILDING I. Design Brief • Background Bridges play an important part in our daily lives, they are essential components of cities and the roadways between populations of people. A bridge is a structure built to span physical obstacles without closing the way underneath such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. There are many different designs that each serve a particular purpose and apply to different situations because some bridges are simple and straightforward; others are amazingly complex. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it. Bridges can be categorized in several different ways. Common categories include the type of structural elements used, by what they carry, whether they are fixed or movable, and by the materials used. The materials used to build the structure are also used to categorize bridges. Until the end of the 18th Century, bridges were made out of timber, stone and masonry. Modern bridges are currently built in concrete, steel, fiber reinforced polymers (FRP), stainless steel or combinations of those materials. Living bridges have been constructed of live plants such as tree roots in India and vines in Japan. Bridges may be classified by how the forces of tension, compression, bending, torsion and shear are distributed through their structure. Most bridges will employ all of the principal forces to some degree, but only a few will predominate. The separation of forces may be quite clear. In a suspension or cable-stayed span, the elements in tension are distinct in shape and placement. In other cases the forces may be distributed among a large number of members, as in a truss, or not clearly discernible to a casual observer as in a box beam. Most bridges are utilitarian in appearance, but in some cases, the appearance of the bridge can have great importance. Often, this is the case with a large bridge that serves as an entrance to a city, or crosses over a main harbor entrance. These are sometimes known as signature bridges. Designers of bridges in parks and along parkways often place more importance to aesthetics, as well. Examples include the stone-faced bridges along the Taconic State Parkway in New York. One of the most important steps in the design process is to understand the problem. Otherwise, the hard work of the design might turn out to be a waste. In designing a bridge, for instance, if the engineering design team does not understand the purpose of the bridge, then their design could be completely irrelevant to solving the problem. If they are told to design a bridge to cross a river, without knowing more, they could design the bridge for a train. But, if the bridge was supposed to be for only pedestrians and bicyclists, it would likely be grossly over-designed and BRIDGE BUILDING unnecessarily expensive (or vice versa). So, for a design to be suitable, efficient and economical, the design team must first fully understand the problem before taking any action. To have student teams return to their bridge design from the pre-lesson assessment and think about the potential loads on their bridge, given the just-discussed engineering design process steps, our task this time is to design and create a model of bridge. • Statement of problem Design and build a double-deck bridge which can pass the car and the train at the same time.The bridge should be 130cm long and 60cm high • Specification 1. The height should be 60cm 2. The length should be 130cm 3. It must be possible to manufacture the design in the classroom 4. The basic material should be wooden 5. It should be strong,durable and finished to a high standard 6. There should be a ship under the bridge 7. It should include recycle and waste materials 8. The bridge should has two floors, one for transportation and the other for train 9. There should be some cars and street lamp which can flash on the bridge 10. There should also be a cross-girder to support the bridge • Target Audience People who are interested in building a bridge and a model or engineers. Government that needs to build a bridge. • Limitation It is hard to buy the materials and draw the sketch. II. Research Solution • Brainstorming a) Each member should show his idea through technical drawings BRIDGE BUILDING Icey Khan BRIDGE BUILDING Mona Jonathan Harden BRIDGE BUILDING b) Get idea from the Internet Mona 1.http://www.design-technology.org/suspensionbridges.htm Today, the cables are made of thousands of individual steel wires bound tightly together. Steel, which is very strong under tension, is an ideal material for cables; a single steel wire, only 0.1 inch thick, can support over half a ton without breaking. Light, and strong, suspension bridges can span distances from 2,000 to 7,000 feet far longer than any other kind of bridge. They are ideal for covering busy waterways.With any bridge project the choice of materials and form usually comes down to cost.Suspension bridges tend to be the most expensive to build. A suspension bridge suspends the roadway from huge main cables, which extend from one end of the bridge to the other. These cables rest on top of high towers and have to be securely anchored into the bank at either end of the bridge.The towers enable the main cables to be draped over long distances. Most of the weight or load of the bridge is transferred by the cables to the anchorage systems. These are imbedded in either solid rock or huge concrete blocks. Inside the anchorages, the cables are spread over a large area to evenly distribute the load and to prevent the cables from breaking free. 2.http://www.madehow.com/Volume-5/Suspension-Bridge.html Once the vertical cables are attached to the main support cable, the deck structure must be built in both directions from the support towers at the correct rate in order to keep the forces on the towers balanced BRIDGE BUILDING at all times. A moving crane lifts deck sections into place, where workers attach them to previously placed sections and to the vertical cables that hang from the main suspension cables 6 After vertical cables are attached to the main support cable, the deck structure can be started. The structure must be built in both directions from the support towers at the correct rate in order to keep the forces on the towers balanced at all times. In one technique, a moving crane that rolls atop the main suspension cable lifts deck sections into place, where workers attach them to previously placed sections and to the vertical cables that hang from the main suspension cables, extending the completed length. Alternatively, the crane may rest directly on the deck and move forward as each section is placed 3.https://www.pinterest.com/pin/125186064618822837/ The Severn Bridge is a motorway suspension bridge spanning the River Severn and River Wye between Aust, South Gloucestershire (just north of Bristol) in England, and Chepstow, Monmouthshire in South Wales, via Beachley, Gloucestershire, a peninsula between the two rivers. It is the original Severn road crossing between England and Wales and took three and half years to construct at a cost of £8 million.It replaced the Aust ferry.The bridge was opened on 8 September 1966, by Queen Elizabeth II, who hailed it as the dawn of a new economic era for South Wales. The bridge was granted Grade I listed status on 26 November 1999. Khan Types of bridge BRIDGE BUILDING Nowadays bridges can be designed using different structural systems. Among these different types of bridge structures are: Beam bridges Box girder bridges Arch bridges Truss bridges Cable suspension bridges Cable-stayed bridges Beam bridges are among the simplest types of bridge structures. Obviously the main actions in this bridge are bending moment and shear forces. This type of bridge structure is normally suitable to be used for short span bridges. Visually, it is not very attractive, but it is easy to construct and cheap. The beam could be made of steel or concrete or wood. Box girder bridge is similar to the beam bridge but the cross-section of box girder is shaped like a box with hollow in middle. In addition the size of box girder is normally much larger than the beam. Strengthwise this type of structure can be used to support a longer bridge span. It is looked better than beam bridge, but still not beatiful. Arch bridges is the type of bridge structure in which its main part supporting the bridge deck is normally shaped as a curve arch. The arch element is supported by abutments at its ends. The main idea in this type of structure is to eliminate or overcome bending moment and shear forces, the main load effects on beam and box girder bridges. By mimicking the shape of moment distribution thoughout the bridge, the main force in arch-shaped element is compression force along the curve of the arch to the supports at each end. Since all bridge loads are transfered abutments, strong abutments are needed to prevent the bridge from spreading out. The bridge itself could be very strong if it’s designed properly. Arch bridges are the oldest types of bridge structures, tend to be very heavy, but could be very beatiful. Truss bridges are the type of bridges supported by triangulated assemblies of slender members (usually made of steel). The members are connected using pin connection and thus the members behave as two-force members. This means that theoretically the members will only experience compression or tension forces, no bending moment and shear force. Normally this type of structure has good strength to weight performance, has lots of repeated parts thus reducing manufacturing cost and can be formed into virtually any shapes and consequently can be very beatiful. Cable suspension bridges are bridges built by suspending the bridge deck from huge main cables, running from one end of the bridge to the other end. The cables normally rest on top of towers and are secured to each end by anchorages. Except on the tower, the main forces acting on this type of bridge are tension forces. This type of bridge can support longer bridge span compared to many other types of bridges, but it is very expensive to build. It is light and strong, but susceptible to wind load if not designed properly. Aestetically it looks very beatiful. Cable-stayed bridges are the bridges in which the bridge deck is supported cables directly secured to towers (pylons). In suspension bridges, the cables are not attached to the towers, transmitting the load to anchorages at either end. So, unlike in suspension bridge, in cable-stayed bridges the pylons BRIDGE BUILDING bear all the load, thus needing stronger pylons. This type of bridge is required less cables compared to that of suspension bridge, easier and faster to construt and is extremelly beautiful. http://www.tekniksipil.org/civil-engineering/bridge-design-and-engineering/different-types- ofbridge-structures/ Bridge Design Considerations in Areas of Seismic Activity While constructing bridges in earthquake prone areas, especially in the seismically active Zones III and IV of the Indian subcontinent, one thing we know in advance is that the chances of earthquakes occurring in such areas are very high. And that is the only thing we know because predicting earthquakes is not yet possible. While designing bridges in earthquake prone areas following things must be considered. Earthquake history of the region is a major factor that needs due attention from engineers. If a particular seismic zone experiences earthquakes of different magnitudes periodically, historical facts will help in predicting the most probable times of the year when an earthquake can happen. Obviously, you do not want to construct a bridge at the time when the chances of earthquake are high. Bridge building for earthquake areas needs extensive study of the earthquake history of the region. Load Factors: Only dead and live loads are considered when designing bridges in non-earthquake zones. However, in quake prone areas, another force is of concern. This is called "seismic load," and it includes the forces on the bridge due to acceleration produced by earthquake jolts. How do we fit seismic load in our design? Historical facts help us to determine the seismic load factor in our designs. In case a region has no earthquake history, a minimum load is considered in design, which varies from zone to zone. San Francisco Oakland Bay Bridge Retrofit Seismic retrofitting is what modern technology has to offer. It not only makes old bridges resistant to earthquakes, but also helps in cost reduction. (Constructing a new bridge is always a time and resource consuming practice.) After a detailed seismic performance evaluation, retrofitting is carried out on old or weak bridges using methods such as friction damper systems, carbon fiber plastic reinforcements, and external prestressing, as well as improving soil properties to keep a check on ground motion. Seismic retrofitting is a relatively new technique but the Civil Engineering societies and associations across the world are promoting it because this is going to save money, time, and resources, without compromising the reliability and safety factor. Minimizing Risk - The Bottomline Japan, the pioneer of earthquake engineering, lost many lives and suffered huge property loss in 2011. Mastering technology is something that we humans can do, but the bottom line is that we cannot beat nature. This does not mean we should be pessimistic or passive; it means that we need to put our best foot forward and try to minimize the risk. Earthquakes won't affect us as much if we are prepared, and the best preparation at this time is to implement earthquake resistant design BRIDGE BUILDING practices and to make the best use of seismic retrofitting technology. An optimistic approach and staying updated with information related to seismic zones and seismic design considerations will definitely help to build better and more stable bridges. http://www.brighthubengineering.com/structural-engineering/117467-bridge-design- considerationsin-areas-of-seismic-activity/Bridge Basics Because of the wide range of structural possibilities, this Spotter's Guide shows only the most common fixed (non-movable) bridge types. Other types are listed in the Bridge Terminology page. The drawings are not to scale. Additional related info is found on the other Terminology pages which are linked to the left. The four main factors are used in describing a bridge. By combining these terms one may give a general description of most bridge types. span (simple, continuous, cantilever), material (stone, concrete, metal, etc.), placement of the travel surface in relation to the structure (deck, pony, through), form (beam, arch, truss, etc.). The three basic types of spans are shown below. Any of these spans may be constructed using beams, girders or trusses. Arch bridges are either simple or continuous (hinged). A cantilever bridge may also include a suspended span. BRIDGE BUILDING Examples of the three common travel surface configurations are shown in the Truss type drawings below. In a Deck configuration, traffic travels on top of the main structure; in a Pony configuration, traffic travels between parallel superstructures which are not cross-braced at the top; in a Through configuration, traffic travels through the superstructure (usually a truss) which is cross-braced above and below the traffic. deck configuration Beam and Girder types Simple deck beam bridges are usually metal or reinforced concrete. Other beam and girder types are constructed of metal. The end section of the two deck configuration shows the cross-bracing commonly used between beams. The pony end section shows knee braces which prevent deflection where the girders and deck meet. One method of increasing a girder's load capacity while minimizing its web depth is to add haunches at the supported ends. Usually the center section is a standard shape with parallel flanges; curved or angled flanged ends are riveted or bolted using splice plates. Because of the restrictions incurred in transporting large beams to the construction site, shorter, more manageable lengths are often joined on-site using splice plates. Many modern bridges use new designs developed using computer stress analysis. The rigid frame type has superstructure and substructure which are integrated. Commonly, the legs or the intersection of the leg and deck are a single piece which is riveted to other sections. BRIDGE BUILDING Orthotropic beams are modular shapes which resist stress in multiple directions at once. They vary in cross-section and may be open or closed shapes. Arch types There are several ways to classify arch bridges. The placement of the deck in relation to the superstructure provides the descriptive terms used in all bridges: deck, pony, and through. Also the type of connections used at the supports and the midpoint of the arch may be used - - counting the number of hinges which allow the structure to respond to varying stresses and loads. A through arch is shown, but this applies to all type of arch bridges. fixed arch, hingeless arch BRIDGE BUILDING Another method of classification is found in the configuration of the arch. Examples of solidribbed, brace-ribbed (trussed arch) and spandrel-braced arches are shown. A solid-ribbed arch is commonly constructed using curved girder sections. A brace-ribbed arch has a curved through truss rising above the deck. A spandrel-braced arch or open spandrel deck arch carries the deck on top of the arch. Some metal bridges which appear to be open spandrel deck arch are, in fact, cantilever; these rely on diagonal bracing. A true arch bridge relies on vertical members to transmit the load which is carried by the arch. The tied arch (bowstring) type is commonly used for suspension bridges; the arch may be trussed or solid. The trusses which comprise the arch will vary in configuration, but commonly use Pratt or Warren webbing. While a typical arch bridge passes its load to bearings at its abutment; a tied arch resists spreading (drift) at its bearings by using the deck as a tie piece. BRIDGE BUILDING http://pghbridges.com/basics.htm Icey 1. http://www.tmgglobals.com/stay-cable Many stayed-cable bridges are designed to last 100 years or more. Clients’ demands for • Long term performance of stay cables; • Leak-proof anchorage assembly; • Reduced footprint during deck erection and stay cable installation; • Installation equipments that is easy and light to use; • Easy maintenance and simple inspection; • The ability to replace cables with minimal disruption to bridge usage; etc had inspired us to develop a Stay Cable System that answers to their demands. 2. http://en.cnki.com.cn/Article_en/CJFDTOTAL-QLJS201103009.htm To check if the force conditions of the stay cable saddle zone of the Shawan Bridge in Guangzhou could meet the relevant requirements in the codes,the model test study of a pylon segment in the saddle zone was carried out.The full-scale model for the pylon segment that could sustain maximum designed cable force was prepared and the force conditions of the segment and the slip resistance of the cables were tested in succession.The finite element model for the corresponding segment was built by the ANSYS and the theoretic calculation was made as well.The results of the test and finite element calculation show that in the process of the test,no cracking appears either in the surface of or in the concrete of the pylon segment,the tensile stress and compressive stress of the concrete can meet the requirements in the design and in the codes,the stress level and deformation of the saddle pipes is low and the action of stress dispersing of the pipes is significant.At the construction stage,the cables will not apparently slip in the saddle and at the completion stage,the slip resistant anchor device of the cables can completely satisfy the requirement of safety factors of the designed slip resistance capacity. At first glance, the cable-stayed bridge may look like just a variant of the suspension bridge, but don't let their similar towers and hanging roadways fool you. Cable-stayed bridges differ from their suspension predecessors in that they don't require anchorages, nor do they need two towers. Instead, the cables run from the roadway up to a single tower that alone bears the weight. BRIDGE BUILDING 3. http://science.howstuffworks.com/engineering/civil/bridge7.htm The tower of a cable-stayed bridge is responsible for absorbing and dealing with compressional forces. The cables attach to the roadway in various ways. For example, in a radial pattern, cables extend from several points on the road to a single point at the tower, like numerous fishing lines attached to a single pole. In a parallel pattern, the cables attach to both the roadway and the tower at several separate points. 4. http://www.fhwa.dot.gov/bridge/t514025.cfm The most effective way to erect a cable-stayed bridge is by close geometric control. Unless the deck is stiff enough to affect cable force, erection control can not be effectively accomplished by force alone (The process is analogous to having a weight on a string--how do you control elevation by measuring force in the string?) Cable length is themost foolproof way to control bridge construction. With saddles, cable length cannot readily be controlled. With prefabricated cables, length control is relatively simple. With in-situ strand cables, it is much more difficult but not impossible when an upper anchor at the pylon exists. With saddles, it is impossible. Geometry control must be forced through deck elevation, which is better than no control, but varies with deck loads and temperature. Both of these effects are avoided when unstressed cable length can be controlled. RECOMMENDATIONS BRIDGE BUILDING Cable stay design and construction practices for cable-stayed bridges have been evolving in the United States since the early 1970's. The recommendations listed below for design and construction practices are basedboth upon current state-of-the-art, United States experience with this evolving technology, and the experience gained from knowledge of international projects. Main tension elements. The "cables" of cable-stayed bridges should consist of parallel strands, approximately 15 mm in diameter, conforming to ASTM A416-90a (or later edition) "Standard Specification for Steel Strand, Uncoated Seven-Wire for Prestressed Concrete," and should be weldless, low-relaxation grade. Epoxy coated strand used in cable stays should conform to ASTM A882, "Standard Specification for Epoxy Coated SevenWire Prestressing Strand." For use in stay cables, epoxy coated strand should be of the type in which the interstices of the strand are filled with epoxy, and the strand should be approximately 15 mm in diameter, weldless, low-relaxation grade. Parallel solid bars should not be used for cable stays. Sheathing. Sheathing should be a high density polyethylene pipe (HDPE) conforming to requirements of ASTM D3035 or ASTM F714 depending upon nominal diameter. Subject to the approval of the engineer, the contractor may propose a white or light colored HDPE pipe, provided it has a demonstrated U.V. resistance equivalent or better than that of a black HDPE pipe. Steel pipe should not be used for the sheathing of cable stays. Corrosion protection. The corrosion protection system should bea multi-barrier, single-phase system that provides both the temporary and permanent system simultaneously, i.e., a system that provides protectionfrom manufacture of the cable throughout its service life. This can be provided by either an epoxy coated and filled strand or the monostrand system (greased and sheathed). Saddles. All stays should terminate at the pylon in appropriate anchorages. Saddles should not be used for cable-stayed bridges. Harden Some advice for make a bridge model 1. Humidity affects the weight of your bridge. Keep your bridge in a closed container with a few grains of rice. or some silica gel packets. 2. Go easy with the glue bottle. As a general rule of thumb, if you can see it than you are using too much. 3. Keep your hands clean! Oils and grease from your skin can ruin your glue joints. 4. Perfect practice makes perfect. The more bridges you build, the better your construction skills will be. 5. Keep your bridge from twisting by using lateral bracing. 6. An L-beam is more efficient than a square, but harder to build. 7. Balsa wood comes in a wide range of densities and stiffness. Weigh each piece that you buy. 8. It is cheaper to buy Balsa in sheets and cut your own wood strips. 9. It’s still true, measure twice and cut once. BRIDGE BUILDING 10. Keep a log of every bridge you build. Record notes and dimensions; you won’t remember later on. 11. Try to videotape testing your bridge. You may get a clue on what failed first. 12. Always keep safety in mind when using sharp tools. Most mistakes are made when you aren’t paying attention. 13. By cutting a piece in half, you more than double its strength in compression. 14. Good lighting when working will help you perfect those little details. 15. Always test your bridge before taking it to a competition, but leave enough time to build another. 16. Draw out your bridge on graph paper to make sure that it is symmetrical. I prefer the 11″ x 17″ graph paper. 17. Different trusses have different ways of spreading out the load. 18. Wood has about the same strength in tension, no matter how long it is. 19. CA glue is a fairly strong, light, fast-drying glue used by many builders. 20. Balsa wood sands very easily. Be careful not to sand off too much. 21. You can mix wood glue with water to cut down on weight. Doing this also helps the glue to seep into the wood, creating a stronger joint. 22. Remember to close your glue bottle when you are done using it. 23. Basswood will bend easier than Balsa wood. Try steaming or soaking your wood to help it bend. 24. Use Lap joints whenever possible to get the best strength. 25. What you want to look for in glue: drying time, price, weight, and strength. These bridge building tips will give you a head start when you start designing and building your model bridges. These tips come from my years of experience starting from my time in the Science Olympiad competition and continuing beyond building for fun. Disclaimer: these tips are my own opinion based out of my experience. Other builders might have different views and we might not agree. I encourage you to try things out on your own and decide for yourself what is the best way to build a bridge. Who knows, I could have been wrong about something. Process of make a model bridge #1: Know the rules! • Be able to define in your own words what the bridge must accomplish • Do not get disqualified #2: Design the bridge • Design the bridge around the loading points • Choose a truss to use • Draw the bridge to scale #3: Gather Materials • Wood • Tools • Workspace #4: Build the bridge • Step One • Step Two • Double check for leaning #5: Testing and Evaluation • Testing Procedures • Evaluation Procedures Related Posts: • 25 Bridge Building Tips • 5 Steps Ebook Updated • What Bridge Design Holds the Most Weight? • Balsa Wood • Testing – Top Loading How to make a LONDON bridge? BRIDGE BUILDING It is easier than you can think and you will need some basic household things to get the job done. You can use safety match or some kind of pins to do but we suggest that you use some kind of wood because wood works better than anything when it comes down to building model of something. This is because it is easy to connect it with other pieces of it and is also easily modified when needed unlike other material such as steel. 1. Understand what you are going to do and focus on it. View different videos, animated explanations and pictures to get a good idea of what that tower really is and how you should proceed to make London Bridge model. 2. If you are living somewhere near London Bridge, go visit it and see everything closely. 3. Take a separate corner in your work shop or garage or house where you won’t end up damaging stuff and get to work. 4. Now take wood and paint it so it looks like London Bridge (or at least close to it). 5. Now see pictures even more closely and start to cut your stuff (wood etc) according to that size. (we can’t give you size explanation because we don’t know the size of model you want to make. So just keep it the way you think is best.) 6. Once you have all pieces cut, call your brother/sister or some friends to help you and start to connect all parts together (without glue, with your hands) and see how model looks. Does it look close to what the real London Bridge looks like? If not, go back and do the edits that you need to do. If it does look close to reality, move onto step 6. 7. Use wood stick (or anything that you have decided to use) and start to attach it with other parts using glue. 8. While attaching parts, keep looking at photos again and again to make sure you put the right pieces at right place. 9. Once done, leave it untouched so all glue can dry up and make things strong. 10. After 1-2 hours, go and show it to your parents, friends or anyone else. Go show it off. That is how simple it is to make London Bridge model and impress everyone around you. We look forward to hearing from you. Good luck for time when you make London Bridge model. Jonathan http://www.historyofbridges.com/facts-about-bridges/types-of-bridges/ Types of bridge: There are 7 types of bridges—arch bridge, beam bridge, truss bridge, cantilever bridge, tied arch bridge, suspension bridge and cable-stayed bridge. Arch bridges uses arch as a main structural component and the bridge are made with one or more hinges. Beam bridges are supported by several beams of various shapes and sizes. Truss bridges uses diagonal mesh os posts above the bridge. Cantilever bridges support their load not through vertical bracing but through diagonal bracing. Tied arch bridges transfer wright of the bridge and traffic load to the top chord that os connected to the bottom cords in bridge foundation. Suspension bridge uses ropes or cables from the vertical suspender to hold the weight of bridge deck and traffic. Cable-stayed bridge uses deck cables that are directly connected to one or more vertical columns. BRIDGE BUILDING http://www.garrettsbridges.com/design/trussdesign/ http://www.garrettsbridges.com/photos/fernbank-bridge/ How to build a strong bridge: 1) Add diagonal braces on the bridge so that it will not be broken because of some torsion. 2) There are three types of trusses commonly used in real bridges: Warren Truss, Pratt Truss, Howe Truss and T Truss ● The Warren truss is one of the most simple yet strong designs. This simple design already existed, but what made the Warren unique is that it uses equilateral triangles. Each side of the triangles are the same length. This marked an improvement over the older Neville truss which did not use equilateral triangles. ● The Pratt and Howe trusses are very similar. In fact, the only difference is the direction the slanted members are angled. This changes which members are in compression and tension. On the Pratt truss, the shorter, vertical members are in compression. However, on the Howe truss, the longer, angled members are in compression. Because most materials (especially wood) that model bridge builders use decrease in the ability to resist compression the longer they are, I think the Pratt truss has an advantage. ● The K truss looks very good on paper. It shortens the lengths of the compression members compared to the other trusses. However, one must wonder if it adds additional weight simply because of the number of members. It is really interesting to note the two green members on the K truss, in theory those pieces could be taken off. However, I had to include them to make the truss design program work. This shows only one orientation of the K truss. If I reversed the direction of the K’s, I wonder how much it would change the forces. BRIDGE BUILDING III. Design and Develop • Final Design BRIDGE BUILDING • Materials Materials Quantity Cost (yuan) Boards 1 40 Glue Sticks 50 10 Nylon Wire 2 10 Bridge 1 800 Small Sticks 3 8 Model Tree 22 12.98 Pigment 1 0 Model Handrail 3 41.4 LED 2 59.4 Total 981.78 • Making Process BRIDGE BUILDING BRIDGE BUILDING BRIDGE BUILDING BRIDGE BUILDING IV. Test and Evaluate Test Performed Pictures Test Results Recommendations T1 T2 T3 Measure the dimension of building Good Good Good The dimension is correct Shake the table gently to imitate an earthquake. Very stable Very stable Very stable The bridge can withstand earthquake BRIDGE BUILDING V. Redesign Reasons Reasons Reasons To imitate the real condition (over the sea) Use a board and paint it blue BRIDGE BUILDING To prevent citizens from falling from the bridge Add barriers BRIDGE BUILDING Plan Isometric Projecion Elevation End Elevation One-point perspective Three-point perspective BRIDGE BUILDING VI. Communication Use PPT to prepare for a presentation VII. Schedule Date Process May 13 Designed which type the bridge will be; Bought materials to prepare for the construction process; Drew blueprints May 14-15 Bought materials; Discussed details of the bridge; Drew blueprints May 16 Discussed details of the bridge; Compared each member’s blueprint of bridges and made a final decision; Finished the final design; Started building the framework the bridge May 17 Finished constructing the framework; Kept on drawing the pictures of bridges; started making the construction process of the bridge May 18 Glued the bridge to make it more stronger; Used nylon strings to strengthen the bridge; Continued making the construction process of the bridge May 19 Continued making the report May 20 Glued the base of the bridge; Wrote the report May 21-May 22 Added lawns to the bridge; Added lights to the bridge; Discussed the layout of the road May 23-May 24 Painted the road and the crosswalk May 25 Glued trees on the lawns; Constructed the beams between the first floor and the second floor May 26 Constructed the beams between the first floor and the second floor; Added handrails May 27-28 Finished constructing the bridge hat are directly connected to one or more vertical columns. BRIDGE BUILDING http://www.garrettsbridges.com/design/trussdesign/ http://www.garrettsbridges.com/photos/fernbank-bridge/ How to build a strong bridge: 1) Add diagonal braces on the bridge so that it will not be broken because of some torsion. 2) There are three types of trusses commonly used in real bridges: Warren Truss, Pratt Truss, Howe Truss and T Truss ● The Warren truss is one of the most simple yet strong designs. This simple design already existed, but what made the Warren unique is that it uses equilateral triangles. Each side of the triangles are the same length. This marked an improvement over the older Neville truss which did not use equilateral triangles. ● The Pratt and Howe trusses are very similar. In fact, the only difference is the direction the slanted members are angled. This changes which members are in compression and tension. On the Pratt truss, the shorter, vertical members are in compression. However, on the Howe truss, the longer, angled members are in compression. Because most materials (especially wood) that model bridge builders use decrease in the ability to resist compression the longer they are, I think the Pratt truss has an advantage. ● The K truss looks very good on paper. It shortens the lengths of the compression members compared to the other trusses. However, one must wonder if it adds additional weight simply because of the number of members. It is really interesting to note the two green members on the K truss, in theory those pieces could be taken off. However, I had to include them to make the truss design program work. This shows only one orientation of the K truss. If I reversed the direction of the K’s, I wonder how much it would change the forces. BRIDGE BUILDING III. Design and Develop • Final Design BRIDGE BUILDING • Materials Materials Q