Contestants will then load sand into the bridge until it fails or holds Your arms feel as if they are being stretched apart. Vertical sides give you no room for error, no latitude for a loading force that is not perfectly vertical i. My friend and I have been trying to make a bridge that can hold max weight and be at most 15g for an efficiency score of The three most common are Warren, Pratt, and Howe. Depending on your design, you might want one wood over the other.
When using an end joint, it is important that you sand the end of your stick so that it makes a flush, "airtight" seal. This bridge was 2. There is more than one way to buy this game. Next Generation Kidsbridge Youth College Adults Life Groups Living Free Orphan Care Mops Care Network Arts Women Extension We believe that God has called us to reach out, not only to those who are in the church, but to our community and to the ends of the earth. Enjoy hours of bridge-building fun with loads of levels to solve, ranging from simple light car bridges to multi-deck draw-bridges and jumps, just to name a few!
Steam Workshop Download hundreds of extra levels from the Workshop!
The objective of Elevated Bridge is to build a bridge which is very lightweight and capable of holding a designated weight. Elevated Bridge is a construction event that involves building and testing a bridge. The main distinction of Elevated Bridge from other bridge events is that a portion of the bridge must be elevated or raised so that there is a "standard minimum clearance" underneath the bridge, between the bridge and the testing base.
Elevated bridges are defined as follows: This can be easily visualized by imagining that the bridge must go over a block. A hole will be located in the center of the test base, in the area underneath the standard minimum clearance. A loading block will be placed above the standard minimum clearance in this area, and a chain will hang from it and hold a bucket that will be loaded with sand. All appropriate descriptions of the aforementioned terms and size specifications can be found in your rules manual.
Start by researching designs and plans for the most stable and lightweight bridge possible. The next step for construction is to draw your plan out. Draw it the exact size you want your bridge, place on cardboard or foam, and cover it with wax paper; you will need to use this to aid in construction. You will need to buy materials with which to construct your bridge.
The rules state the bridge must be constructed only of wood joined by glue. Research the strengths and weaknesses of different woods and glues. Remember, ultimately you want the lightest but strongest bridge. Try to be exact when cutting the pieces. You can use band saw and sand the ends to the correct angle. There are a countless number of designs for a bridge. Bridges are designed using trusses. Many different truss structures exist. The three most common are Warren, Pratt, and Howe.
The Warren truss features truss members that form equilateral triangles. Each diagonal is subject to the same load, with every other member alternating between tension and compression. The Pratt Truss contains right triangles in its design.
The slants face the center of the bridge. The Howe Truss is similar to the Pratt Truss, except the slants face away from the center of the bridge.
The difference with the Howe Truss is that the slants become compression members and the vertical members become tension members. There is no preferred truss design. When designed and built correctly, any of these truss designs can work well.
Other, less common, truss designs can be as or more effective depending on how they are used. Before building any bridge, it is critical to design the truss and calculate loads with a truss analysis program. Many such programs exist. The simplest is from John Hopkins university, and can be found in the link below. Other, more featured programs, include MDSolids and Dr. The design of one face of the bridge should be constructed in the program. Then, the load can be applied to the center of the bridge, and the stress in each truss member can be calculated.
This information is extremely important when designing the bridge. Generally, it is better to use stronger or thicker wood in areas with greater stresses. Sides angled in a bit might help your design, but it is not the same for everyone. Vertical sides give you no room for error, no latitude for a loading force that is not perfectly vertical i.
When you look at a table of cosine values, you will see that in the first few degrees, it is a VERY small factor. Courtesy of Balsa Man. Compression and Tension are the two primary forces acting upon your bridge. An easy way to think of compression and tension is the direction in the which the force is being applied.
Stand across from another person. Put your hands on each others shoulders, and lean in. You are experiencing compression. Another way to look at it is if you sat on top of a table. The legs of the table would be under compression. When wood is under compression, it tends to buckle. You generally want slightly denser wood for areas of compression, depending upon the amount of compressive force.
Hold hands and lean back. Your arms feel as if they are being stretched apart. Another way to think about it is if you had a pencil and you held it with both hands at opposite ends, and pulled at it from each side.
When wood is under tension, it tends to snap. You generally want a flexible piece of wood for areas of tension. Here is an image of Compression and tension working on a triangle, if the triangle was loaded with weight at the top:. The more bridges you build and break, the more you will learn, and thus the more improvement you can make. It is important that you test as much as possible. Every broken bridge will help you improve with your next bridge. One helpful testing mechanism is a "safety tower.
A rig that stops the loading block from falling once the bridge has broken will allow the bridge to remain intact after the initial failure, without any secondary damage. This allows the point of failure to be identified. The best way to build a bridge is as two 2-dimensional faces.
A template can be drawn out on poster board. Attach wax paper over the template to ensure that the bridge is not glued to the template. Use pins to help keep pieces in place. After both faces of the bridge are constructed, they must be put together. A jig that holds the sides parallel is useful in this situation.
Lateral bracing refers to bracing between the two sides of the bridge. Generally, lateral bracing is important on the top of the bridge, as that portion is in compression.
When materials are in compression, they tend to bow and flex. The bottom of the bridge is in tension, which does not bow and bend, thus, lateral bracing is not required in these areas.
Bridges can be made out of any type of wood except those excluded in the rules, such as particleboard, plywood, bamboo,etc. Balsa has the highest strength-to-weight ratio of any commonly available wood, and is readily available in many sizes at your local hobby shop. When selecting balsa, it is important to ensure that all pieces used are of appropriate density. This can be found by weighing the wood with a pocket scale.
One should also ensure there are no identifiable defects in the wood grain, as this may cause premature failure. You can buy balsa wood in sheets and cut out your own sticks or buy pre-cut sticks. If you choose to buy in sheets, look out for the grain of the wood. There are 3 kinds of grain: A, B, and C. A grain is more flexible and is best for tension members. C grain is more stiff and good for compression. B grain is a combination of the two.
Basswood is also commonly used in bridges. It is stronger than balsa, but also much heavier. It can be very effective when used strategically. Different bridges use different wood. There are pros and cons to both:. The kind of wood you use is completely up to you. You can build strong bridges with either kind of wood.
Depending on your design, you might want one wood over the other. If you have many pieces in your design, you might consider balsa, as it is lightweight. But if you have few pieces but still want a strong bridge, bass is the way to go.
If you find that there is a joint that is constantly the fault of your bridge, you might want to change that piece to basswood. The wood may be bonded by any type of glue. This includes wood glues, cements such as Duco or Ambroid, and CA. CA works very well for bonding bridges. It is available in various viscosities. Thin CA will seep into the wood at the joints, thereby strengthening the overall joint.
A medium viscosity seems more like a gel, it also seeps into the cracks, and when completely dry, is fairly stronger than thin CA. However, medium viscosity takes a few minutes longer to dry than the thin. It also cures in seconds, facilitating the construction of the bridge. Wood glue is also strong in bonding any type of wood, although it is heavy. It also takes much longer to dry. When using any type of glue, it is important to use the appropriate amount. A little glue can go a long way, and using too much glue is a very easy way to drastically increase the mass of a bridge.
There are quite a few CA glues, which include Krazy Glue, Insta-Weld, Permatex, Zap-a-Gap, and many more. Most if not all can be found at a nearby hobby-shop, online, or just at your nearest department store. There are various joints that you can use when building a bridge.
There are 3 main kinds of joints: This joint is bad for tension, because the two pieces will pull right apart. When using an end joint, it is important that you sand the end of your stick so that it makes a flush, "airtight" seal.
If there is a small gap the glue must fill, the joint will be significantly weakened. Lap Joint The lap joint is one of the strongest joints. You place the side of one stick on top of the side of another stick. This joint helps compression members to not bend. Lap joints have more surface area for the glue to work on than the end joint. Notched Joint The notched joint is probably the hardest to build and is stronger than an end joint but weaker than a lap joint.
In this joint, you cut a small notch in one of the sticks than place the end of the other stick in the notch. Due to the difficulty of making this notch, it is not commonly used.
However, you can make a gusset to make the joint as strong as a lap joint. A gusset is made by placing a thin piece of wood over the joint, thus covering the crack between the wood. You can make an even stronger joint if you place a gusset on both sides of the joint.
By adding more gussets, this would increase the surface area of the glue, and it provides more stability. However, do not use too much glue, as it is only needed for a thin coat where to pieces meet. During testing, the bridge will be placed on the test base, so that it touches only within the bearing zone. The competitors will then assemble and place the loading block on or within the bridge, so long as it is above the standard minimum clearance.
An s-hook will be used to suspend a chain from the loading block, and the chain will support a bucket that is approximately one inch off the floor. Contestants will then load sand into the bridge until it fails or holds At that time, the bucket of sand will be weighed, and the structural efficiency determined.
Structural efficiency is found by dividing the mass held by the bridge by the mass of the bridge itself. Generally, these measurements will be in grams, although any units of mass may be used, provided they are the same. If you are using a scale that measures in pounds lbs then the maximum load is 33 pounds. For instance, if your bridge weighs 10g and you hold 15 pounds, you would multiply 15 pounds by to convert it to grams. This would get you grams.
Then you would divide by 10g the mass of your bridge and your efficiency would be Google will also convert measurements. There are events similar to this one, in which you build a wood structure that is light and stable.
The physics of these are different, but the general concept is the same. New York Coaches Conference. The Diary of a Bridge Builder. Online Tool for Calculating Forces in Truss and Frame Structures. From Science Olympiad Student Center Wiki. Stevenson High School The objective of Elevated Bridge is to build a bridge which is very lightweight and capable of holding a designated weight.
Retrieved from " https: Event Pages Building Event Pages. Navigation menu Personal tools Log in. Views Read View source View history. Navigation Main Page Forums Test Exchange Image Gallery Chat Recent changes Random page Help. Tools What links here Related changes Special pages Printable version Permanent link Page information.
This page was last modified on 5 Juneat Content is available under Creative Commons Attribution unless otherwise noted. Privacy policy About Science Olympiad Student Center Wiki Disclaimers.
There are no tests available for this event. There are no question marathons for this event. Daniel Wright Junior High School.
Elevated Bridge - Science Olympiad Student Center Wiki
A T beam is an engineered beam that looks like a T. The physics of these are different, but the general concept is the same. Try to be exact when cutting the pieces. This allowed the edges of the bridge to rest on the supports, with a little less than 1cm of overlap on each side.
The bridge did much better than I thought. All the truss members held spread the load from the load point to various points on the arch. Recent updates View all 29 13 June Poly Bridge out now on iOS Exciting news today! Another way to look at it is if you sat on top of a table.
Lap Joint The lap joint is one of the strongest joints. I am building a bridge for a a science Olympiad competition. Visit the website View the manual View the manual View update history Read related news View discussions Find Community Groups.
Science Olympiad Bridge | Garrett's Bridges
The Pratt Truss contains right triangles in its design. Research the strengths and weaknesses of different woods and glues. CA is very common in Science Olympiad. Similarly, it is very important to build your bridge perfectly vertical, with no lean at all.
Enable Reviews Beta what is this? Click here to visit the User Gallery. When you look at a table of cosine values, you will see that in the first few degrees, it is a VERY small factor. Online Tool for Calculating Forces in Truss and Frame Structures. I attemped to make a souped-up version of this bridge after the competition, but my enthusiam gave out and I never finished it.
This puts the longer arch member in tension and the shorter, straight loadbed member in compression. Sign in to add this item to your wishlist, follow it, or mark it as not interested. Then you said that it was A rig that stops the loading block from falling once the bridge has broken will allow the bridge to remain intact after the initial failure, without any secondary damage.
I built it in , and it is now What size Basswood did you use? How did you get the Basswood to arch? It may be able to get a score of close to , which would put it close to the national winning bridge back in How is this constructed?
My favorite glue is a rubberized cyanoacrylate CA that you can find in hobby shops.
4230 :: 4231 :: 4232 :: 4233 :: 4234 :: 4235