Spaghetti is a very thin element. If you wish to design a bridge using it, there are only two configurations possible to give you the best possible result. Either a truss or a funicular shape. A truss is a configurations of triangular members. There is a top chord and a bottom chord, with the top chord always in compression and bottom in tension. Now, I would give you a useful piece of advice over here. Make sure you use nearly 3 times more spaghetti in the top chord of truss than in the bottom chord. The sole reason being that the top will buckle if it is not strong enough.

I would recommend you to go a for a similar configuration. The only reason being, it is funicular as well as it has triangles in it. It will give you the best result possible. Just make sure, the two big inclined members should have more sticks than the bottom deck and you will have a good result.

Times have Changed! We were never to ‘play with our food’.

But today:

1. How to design and build a Spaghetti bridge that carries ...https://www.quora.com/How-do-I-design-and-build-a-Spaghetti-bridge-that-carries-more...Nov 08, 2015 · You can find some the best advice in this previously answered question here: How to design and build a spaghetti bridge? While your question is rather specific to your particular design task, you don't mention any other restriction therefore my ...
2. Most efficient Truss type bridge to make out of spaghetti ...https://Home | Yahoo Answers/question/index?qid=20091223111229AAXRL2VDec 23, 2009 · Most efficient Truss type bridge to make out of spaghetti for physics class? The objective of this project is to build a model truss bridge of spaghetti that can hold a load of 2500 grams on a 40.0 cm span.Status: OpenAnswers: 4
3. Popscicle-stick bridge: What's the best design?https://slate.com/human-interest/2013/12/popscicle-stick-bridge-what-s-the-best-design...The bridge will be loaded midspan, like a point load, and there’s no limit on the number of Popsicle sticks, but there’s a 1 kg maximum weight, so strength-to-weight ratio must be greater than ...Author: Quora Contributor
4. Freshman Clinic I, Section 3, Spaghetti Bridgehttp://users.rowan.edu/~everett/courses/FECI/spagBrdge.htmI suggest building a bridge that is close to the maximum weight and hold as much weight as possible. his may require an interative design process, designing the bridge for different loadings. Most designs will consist of two identical truss systems, side-by-side.
5. [PDF]Spaghetti Bridge Lab - slapt.orghttp://slapt.org/resources/labs/Spaghetti_Bridge_Lab.pdfMost of the items they suggest will fall into two categories: bridge design factors and measures of bridge strength. Students can choose the design factors, therefore those factors are the independent variables. Suggest that the bridge design factor of interest is the number of spaghetti strands. The design of the bridge will determine how many ...

I was part of a team competing in the Spaghetti Tower Marshmallow Challenge.

Our structure was average so I spent a week afterward testing new ideas. Most people use the spaghetti to support the structure. I came up with a totally different idea which blew all the others away.

Here are the materials you receive to compete.

Twenty strands of uncooked spaghetti, one yard of masking tape, one yard of #16 cotton string and a fluffy marshmallow. You have 18 minutes to act as a team to build the tallest structure to support the marshmallow at the top.

Here is a killer way to beat the competition-

Unravel the string into 16 individual pieces. They will be guy wires.

Use all the spaghetti for height not support. Bundle the full-length spaghetti into 3 piece units, offsetting them by 1/3 to spread out the weak joint points. Use tape to strengthen each joint. Attach the guy wires (string) at various points to the structure on a triangle basis to the base.

I suggest that you build the spaghetti core in 3 or 4 units before assembling wait about 10 minutes into the competition so others don’t copy your idea.

Very carefully add the marshmallow just before the competition ends.

Here is a link to an article I posted on my blog about the process.

Spaghetti is not completely dry even in the box. Rewetting it will give a chance for soluble starches to reorganize and fill in cracks and scratches then dry hard with second drying. This sounds good for a bridge but not for taste of the pasta. Now, about the baking for strength. Moisture will toughen the material and allow some give before breaking. However, breaking strength is reduced because the starch molecules are set farther apart with the absorbed moisture. Raw strength will be higher if baked. However again, the finished bridge will have to be kept dry and leaving it in air will not do. Also, if you use a water based glue the water will soak into the pasta and make a weak spot at each joint. If you want to keep the strength at its peak up to the testing time, since the test will occur after storage in a classroom for hours and get moist, keep it room temperature dry with 40% humidity or so and live with that. Now, if you read this far, I will tell you a better thing to do to ensure strength: take a dozen or so sticks and bend them in a 3 point bend test until one or two break. Those are the weakest links and too damaged to help you. Keep the winners to build your bridge. Also, the broken ones are probably stronger because the weakest point is taken out of the picture by breaking. So these may ne good for short runs. Also, equally important is the type, brand and source of the pasta you use. Italian pasta might be stronger than the american pasta because they use more expensive semolina flour. The composition of the pasta will impact strength. Adding fillers to cheapen the product as is often done for bargain food, will weaken the material. Do not compare one stick against another until you know the diameter is the same. Otherwise, calculate the strength in a bend test for the square cross section area to account for fat pasta. Note also that a fat pasta might build a weak bridge compared to the thinner pasta. If you want to get finicky, line up the wider dimension of the pasta with the stress direction (up down for a bridge) to raise moment of inertia. Don’t be afraid to build beams like an I beam from multiple sticks and then build with just a few of those beams. Usually there is a penalty for weight depending on the level of education you are in. If the rules are lax, then a big heavy bridge will win if good engineering is applied. If there is weight penalty, then every trick is important.

Suspended box frame truss. When performing bridge design, it is important to create as many tension members as possible given your materials. After you construct this deck, you can add a riser and then place your string at the critical points (joints) of your box frame. Just like in a suspension bridge.

Create a trussed bridge paying attention to how the joints are made - and make it strong in three directions so it doesn’t distort under load. This can give a very efficient structure. You can eliminate ten straws from the structure I illustrate to create a variant of the engagingly-named Pratt Truss.

There are lots of real world examples based on Warren and Howe designs. If you have straws to spare double up the compression members. You can use the string for members that are in tension only - but a true suspension bridge may not count as ‘sturdy’ since it relies on how it is anchored to the abutments. Worth knowing how/where the load(s) will be applied as that can result in failure long before the bridge goes. If it is within the ‘rules’ and you are providing the materials you can use different brands of drinking straws which have slightly different diameters and insert one into another to legitimately beef up the struts.

A2A:
I found a couple of sources that may be useful to you.
First is a step-by-step process from Buncombe County Schools showing how to use templates to plan and lay out the design: How to build a pasta bridge - WD-STEM

Second is an ehow set of directions that includes some useful tips for designing and building the bridge: How to Build a Spaghetti Bridge | eHow

Finally, if you want a more detailed, scientific examination of the concepts involved in building a spaghetti bridge, here's a set of hints in a Power Point from the someone at Johns Hopkins University: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=0CFUQFjAI&url=http%3A%2F%2Fpages.jh.edu%2F~virtlab%2Fcourse-info%2Fei%2Fmisc%2Fbridge_summary.ppt&ei=8AyPU_j_Eqa78QHPiYC4Bw&usg=AFQjCNGHWTQ7JEtmAwAz3TAbh7NyAwiMZA&sig2=dsARkvYsFNIdlzZeZm6PBA&bvm=bv.68235269,d.b2U

Hope this helps!

Based on all of the "MIT" tags I'm seeing, I'm going to assume this is a college level research project/contest and not an elementary school one.

The first thing you will need to do in order to design anything is know the strengths of your materials. 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.

Assuming you are involved in structural engineering (which I assume you would be, because otherwise why are you taking part in this project?), you probably know that tensile strength depends only on the area of the cross section. Compression strength is usually governed by buckling, which depends on the slenderness ratio. Keep your compression members short and stocky if possible.

After that, you follow the regular structural design process. Design a configuration and use Statics to calculate the forces on each of the individual members from your load. Then, based on your previous testing, determine what kind of spaghetti element you need to put there in order to adequately resist that load.

For a college level project, I would expect to see your load testing results for individual spaghetti members (i.e. Tensile strength vs. area, compression strength vs. length for a given cross section), as well as your static load calculations.

I assume you're going to build this bridge for a project (practical) and not as an assignment (only theory, on paper). The bridge is of a single span of length (?) assumed short (50 cm or less).

If you would like to minimize the weight of the bridge, a truss bridge is definitely worth considering. If the rules permit, an arch bridge with the arch "underneath the loaded portion" is also definitely worth considering. As long as the arch is horizontally restrained at the ends, it's capacity will definitely be sufficiently high. But please double check the support conditions if you decide to go for the arch (No part of the bridge cannot extend below the surface level at any point ?).

If the organizers provide only roller supports at ends then going for a truss option looks best. If the end supports can be pinned (horizontally and vertically restrained), I think an arch type bridge model would be better. There is no definite answer for this type of problems (So and So bridge type is the most efficient in strength / weight ratio).

Overall, I would suggest you to pick a short span bridge (google images) of your chosen type and follow the pattern of member distribution (cross bracing etc.) adopted in that structure.

Often, it is not the wooden part that is the problem but the connections (glue) that fail under loading (tension). If you plan on using strong industrial grade glue, then you're probably safe but if not, minimize the members in tension and use additional tension members (threads) to reinforce those areas. Also try to minimize the number of joints, overall.

It is also definitely useful to reinforce the middle portion (region where it is loaded for testing) to avoid local failure.

If you have to minimize the weight, use material sparingly for the deck part (which is not structurally active, in your case).

Usually, the winners are decided by the structure having the maximum strength/weight ratio.

Cheat sheet rule #1: Theoretically, for the same structural members, increasing depth will increase weight linearly (x1) but will increase capacity exponentially (x3) since inertia (stiffness) varies as depth to the power 3. Changing width of the members will not have any influence whatsoever. So forget about reducing weight of the structure and focus on increasing its strength. The ratio of strength/weight will always increase.

The best solution for this topic is a "thick log of wood". The organizers will run out of loads to put on your 'bridge' :D

Strength ? infinity. Weight ? who cares ?.

Cheat sheet rule #2: If using threads (rope) is allowed, just lace the whole structure using a couple of threads (continuous thread going across joints). This will ensure better load capacity but I guess it's cheating :)

Cheat sheet rule #3: Don't try to test your bridge before submitting it. Better to make two models, use one for your testing and the other one for making the improvements based on the performance of your first trial bridge. If you do test your bridge, reinforce all connections (glue part) before submitting your model.

Hope I helped :D Good luck !!

There is a lot of math an engineering that goes into deciding this, however what you are referring to is something called a safety factor. Most structures (including homes) operate under a margin of error. Structural components are always sized up, not sized down, and all bridges for example are engineered for the worst case scenario.

(This is going to be an extremely simplified explanation as the structural analysis gets pretty complicated) when a car loads onto the bridge, the weight first bears down on the slab. In turn, half the weight being applied goes to one beam (or girder) and the other half of the weight goes to the other beam. After the beam collects the weight, one half of that load goes to one cap or bridge seat, and the other half goes to the next adjacent cap. Again, once that has been collected, half the load goes to one column and the other half to another column. You can use the terminology Ive used to follow along in the picture. Eventually the entire accumulated load collects into the footing, which distributes the weight and prevents sinking of the foundation or pile cap. But what we really care about in wondering how we keep a structure standing, is are the beams sized properly for the load that is being applied. In order to size beams, we need to analyze the material being used, and its ability to resist moment, shear, compression, and tension forces (all of which have their own mathematical formulas to which they are applied).

Mr Phillips is correct. I am posting only to give him an incident which supports his answer. I am a retired engineer who does some tutoring.

I was tutoring a Middle School young Lady in math. She asked, just in passing, what shape is the strongest. I answered “Triangle.” “Why?” “Only ways to break it are to deform one of the sides, or to part one of the connections.” She asked for a demo, and we showed it with toothpicks. This was about 6th or 7th Grade. We went back to math.

TWO YEARS LATER, her mother phoned me excitedly to announce the young Lady had just won the school's Science Prize.

The class had been divided into many teams of a few students each, and given a package of popsicle sticks and a tube of glue each. Each team was to construct the longest possible bridge capable of carrying a toy electric car.

Our heroine suggested triangles. Her team refused this “dumb idea.” She forcefully, but diplomatically, urged that they watch her demo the idea. Then she led the team in constructing the bridge, forcing craftsmanship at the joints, careful planning and measurement, etc.

Of course her team won. This competition had been done for several years. Hers set a new weight-carrying record.

But then she insisted on explaining. She gave a true scientific lecture, but worded so that 8th and 9th Graders followed it. THAT was cited in her winning the Prize.

I am not telling this because I had made an offhand remark, but because of her leadership, craftsmanship, and the lecture AS WELL AS the bridge.

So, Mr Phillips is right

All kids like building things! Whether we're stacking LEGO® blocks or playing cards in the living room, sticks in the forest, or sandcastles on the beach, we're all architects and builders at heart. Think back to the last time you made something in this way. What was the biggest problem you faced? One of the things that would have worried you were the possibility of your building toppling over once it reached a certain height. That's also true in the real world, where the number one problem any builders face is keeping their structure upright.

The trouble is all to do with the gravity-like force of attraction between any two objects in our universe. On Earth, we see gravity as a tendency for things to fall toward the floor, but gravity always works two ways. If you drop a pen, it does indeed fall toward the floor—but the floor also jumps up by a microscopic amount to meet it on the way! The force pulling your pen down toward Earth is exactly the same size as the force that pulls Earth up toward your pen.

Triangles. Pasta is pretty strong in compression.

I would build a truss structure like this.

We had essentially this problem in a structures lab in school. The problem is a bridge spanning 12”, 2” wide (essentially your 5 cm) and maximum 4” deep, loaded in the center. We were limited to balsa wood, paper or toothpicks and Elmer's white glue. The bottom chord is 1/8” thick, the diagonals are 3/8” thick box beams (columns really) made of 1/16” sheets and webs. It weighed 24 grams and had the bottom chord fail in tension at a load if 248 pounds, if memory serves. This is the simplest truss, a single triangle.

(sigh) Youngsters trying to cheat themselves of an education. These kids go for the goals like aquarium fish for fish food. Maybe we shouldn’t be awarding prizes for the best design. Maybe we should award prizes for most attempts made while coming up with a design, or best use of previous attempts to come up with new designs. But that would be harder for the educators to evaluate, and we can’t have that.

Sure, try Jeffrey’s idea of a truss. See where it breaks, and try to figure out why it breaks there. Change the design and repeat, maybe three or four times. If you do that, I’d be 100% satisifed as an educator and parent.

To design a bridge to support a heavy load, consider the following steps:

1. Determine the load capacity: Calculate the total weight of the vehicles, cargo, and other loads that will be crossing the bridge. This will inform the size and strength of the bridge components.
2. Select the appropriate materials: Choose materials that are strong, durable, and able to withstand the loads and environmental conditions. Common materials used in bridge construction include steel, concrete, and wood.
3. Determine the bridge span: The span is the distance between the bridge's supports. Choose a span that meets the functional requirements while minimizing the size and cost of the bridge.
4. Determine the bridge height: Consider the height of the bridge deck and the clearance needed for boats, vehicles, or other obstacles.
5. Choose the bridge type: There are many types of bridges, including beam bridges, truss bridges, arch bridges, suspension bridges, and cable-stayed bridges. Choose the type that best suits the site conditions and load requirements.
6. Select the foundation type: The foundation provides a solid base for the bridge. Choose a foundation type that is suitable for the soil and geology of the site.
7. Design the bridge components: Design the bridge components, such as the deck, piers, beams, and cables, to withstand the loads and environmental conditions.
8. Perform structural analysis: Use computer software or mathematical models to analyze the structural behavior of the bridge and ensure that it meets the load and safety requirements.
9. Consider maintenance and sustainability: Plan for the ongoing maintenance and sustainability of the bridge, including the materials, coatings, and corrosion protection systems.

Hope you got the answer of your question!!!

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Thanks for reading :)

Q: What is the most efficient design to build a spaghetti bridge? This means it has a low weight and high strength. The requirements are that it has to hold at least 20 times its weight.

A: Depends…..is the spaghetti raw or cooked?

What is the most efficient design to build a spaghetti bridge? This means it has a low weight and high strength. The requirements are that it has to hold at least 20 times its weight.