Suggest they bring them to the testing station to check the length. The Baltimore truss bridge is a variant of Pratt truss Bridge. King post is the main component of this structure and connects the top portion of the bridge to its base. The diagonal elements are under compressive forces. It is assumed that only the tensile and compressive forces operate on the truss elements. Spaghetti has strong axial tension but weak compression, so it is best to make compression lengths as short as possible and add internal web members. Only ten Pegram bridges remain in the United States, and seven of them are in Idaho.
Students can also use toothpicks and popsicle sticks as alternate materials. If the connections are too rigid, when the bridge starts to deflect, the joints will twist and rotate and put added bending force into the spaghetti. These are all excellent skills to teach your students through engineering projects, and luckily there are some great teaching moves to help. While this type of bridge is easy to construct, engineers must make sure that it lasts and is safe to use. To expand their knowledge of forces, consider teaching students the forces that hold a bridge up - compression and tension. Wooden bridges were soon replaced by models or wood-and-iron combinations.
It allows a teacher to show the relationship between the bridge's total weight and the weight it can hold. For larger bridges, consider using something like bags of sand or, if your bridge is quite large, actual weights from a weight set. The truss bridge comprises vertical, horizontal, and the diagonal elements. The type of glue you use will make or break your bridge. The reduction in length enables these components of the bridge to endure the compressional force. Each type could be the best for a specific situation, and there are a ton of factors that engineers must consider when choosing which one to use. Constraining all translational degrees of freedom at the leftmost horizontal edge prevents any rigid body motion.
Although no charge or fee is required for using TeachEngineering curricular materials in your classroom, the lessons and activities often require material supplies. Building a Spaghetti Bridge Now, it's time to get started planning the actual engineering project. The other two group mates are frustrated with the group and are losing interest in the project. As stated above, epoxy is the strongest bonding agent you can use. Students should know about forces in general, including gravitational force and tension. See more ideas about Spaghetti bridge, Bridges and Bridge design. Yes No Thanks for your feedback! This is a rare type of truss bridge originally patented in 1840 by William Howe.
Their efforts weren't for naught. These engineers must consider many variables when creating plans, such as the distance to be spanned, where the bridge is being built, the expected type of traffic it will have to withstand, materials available, budget and what the bridge will look like. Civil engineers design structures such as buildings, dams, highways, bridges, roller coasters, tunnels, skyscrapers, and sports arenas, among many others. Again, the size and density of the weighted objects will depend on the size of the bridge you built. The vertical elements are under tension. An inverted triangle is more stable than a triangle with the apex on top. Let's look at how to set up this experiment and the concepts demonstrated.
However, when we are considering small model bridges, I have a hard time seeing the Howe as efficient as the Pratt. Additional support is provided in the form of vertical and diagonal sections which have half the length of main sections of the bridge. Keep your compression members short and stocky if possible. Grades 6 - 8 Do you agree with this alignment? The maximum length of a Pratt truss bridge can be 250 feet; this bridge is generally used for railroads. In the K Truss bridges, length of members which undergo compression is reduced. Grades 6 - 8 Do you agree with this alignment? Second, an eigenfrequency analysis shows the eigenfrequencies and eigenmodes of the bridge. This is why we have I-beams, which provide more material on the tops and bottoms of beams to better handle the forces of compression and tension.
In this Article: Dry spaghetti is very brittle and breaks easily, but by gluing the strands together to create different shapes, you can make a model bridge that can hold a surprising amount of weight. Wax paper can also be positioned over a graph paper drawing, allowing you to see the design. Bowstring Arch Truss This bridge was patented in 1840 by S. For smaller bridges, coins will work as weighted objects. In fact, if the ends of the spaghetti are cooked and weakened at the joints, then the bending forces from the joint twisting will break the spaghetti very quickly. Assuming you are involved in structural engineering which I assume you would be, because otherwise why are you taking part in this project? The simple design of a Pratt truss bridge makes it useful to hold everything from pedestrians to trains. A number of schools, school districts, science museums, universities, and engineering-oriented groups hold spaghetti bridge building competitions.
In order to do this, you will need to do load tests of your individual spaghetti strands to see how much they can take. Figure out their tensile strength, compressive strength, and possibly flexural strength if you're using them that way in various lengths and configurations. Grades 6 - 8 Do you agree with this alignment? Another could be in charge of glue, and perhaps another in charge of checking to make sure the structure is following their blueprints. Planar truss, on the other hand has a 2-dimensional design. Design your bridge on a sheet of graph paper first. Red is tension and blue is compression.
To help generate ideas, show students the example truss bridge designs in Figure 1. Also, you want to make sure you have plenty of pasta on-hand to make the necessary reinforcements to your bridge. For tips on how to enter your bridge into a competition, read on! Bailey Bridge This bridge is normally utilized to cover obstacles by the military tanks and other equipment. Rounded spaghetti noodles may be better for some parts of your bridge while flattened noodles, like linguine, may be better for other parts. The former design has the bridge elements under compression, while the elements of the later design are mostly under tension. So, make sure you account for the weight of your bridge when designing your bridge.