4 Popsicle Bridge Designs

Picture this, you are back in 7th grade. You’re sitting in science class with a group of friends staring at a pile of Popsicle™ sticks and a bottle of glue. While you may not have realized it then, you learned some valuable information engineering through that project. Yes, now would be a great time to thank those awesome science teachers. If you remember, you probably learned about four different types of bridges found around the world. Whether you’re a student looking to win a science fair project or a parent that has been recruited to help, here are four bridge designs you may consider (P.S. Here's the original video).

Beam Bridges

 beam bridge

This bridge is made of a long beam, usually steel, that runs from one end to the other. This would be the simplest bridge you built in science class. It looked something like a flat walkway. It is held up by concrete blocks on either side. In order for this bridge to work, it must be made of stiff material making it able to resist bending and twisting under the weight of heavy loads. A great example of this type of bridge would be the Lake Pontchartrain Causeway Bridge in Louisiana. The longer of the two bridges is 23.83 miles long.

 

Truss Bridges

 truss bridge

A single beam, no matter what the distance, receives a lot of compression and tension. The top beam receives the most compression and the bottom receives the most tension. The middle beams, however, experience very little compression and tension. I-beams provide material on the tops and bottoms of beams to help the upper and lower beams handle these forces. If you think back to your project in science class, this would be the bridge with the cool triangles. The triangles dissipate a load, essentially transferring the weight from a single point to a wider area. This build allows for longer bridge length. The Warren Truss Bridge in Kansas would be an excellent example of this type of bridge. This was one of the first truss bridges ever built.

Arch Bridges

 arch bridges

I am sure a few Popsicle™ sticks were broken on this one. The arch bridge was the hardest to build but man, was it cool. Made up of a series of arches that run underneath the bridge deck, this bridge is one of the most popular types of bridges. This bridge conveys load forces along the curves of the arch supports at each end. These support ends, called abutments, carry the load of entire bridge.

The abutments are responsible for holding the arch in an unmoving precise position. The keystone at the top of the arches pushes the surrounding rock down and outward, making the structure very strong. A very commonly known arch bridge would be the Sydney Harbour Bridge.

Suspension Bridges

The last bridge you built was the suspension bridge. For those of you that don’t remember it by name, yes, this was the one where you got to use yarn. This bridge can span anywhere from 2,000 feet to 7,000 feet long. The roadway is suspended by cables, ropes, or chains depending on the bridge. The cables run along two tall towers which are located on either side of the bridge.

These towers support majority of the weight as compression pushes down on the deck of the bridge and travels up the cables. Once the towers receive the compression they dissipate it directly into the earth. The supporting cables run horizontally between the two anchorages, which are made of massive concrete blocks or solid rock. These cables receive the bridge’s tension forces. The best example of a suspension bridge would be the Golden Gate Bridge.

These four types of bridges are found all over the world today, and we rely on some of them every day for getting to and from where we need to be. That being said if you are thinking about building a bridge, you need to consider the importance of having a structure that is reliable and built with the right materials. Contact a structural engineer and get their opinion on the best way to build your bridge.  After all, this isn’t 7th grade, and you aren’t using Popsicle™ sticks. Get help from the pros, call Anderson Engineering today.