~ Thomas Otter
KCFS Teacher
~ Thomas Otter
KCFS Teacher
Embedded Files
KCFS Teacher
Taiwan has many rivers that we need to get across every day to get from one place to another. Just in New Taipei City alone, there are the Tamsui, Xindian, and Keelung Rivers. It’s thanks to bridges that we don’t have to swim or take a boat to get to school in the morning! From the Old Donghe Bridge in Taitung to the Danjiang Bridge in Tamsui, bridges in Taiwan don’t just carry heavy loads – they look beautiful as well!
In our Building Bridges project, we tasked students with building their own work of engineering art. In order to build a bridge, they would first need to learn about the forces and fundamental elements of bridge design. In the end, they learned to appreciate the skill of the engineers who constructed the bridges we use every day.
Getting Started
Students discovered that compression and tension are the important forces they needed to think about in order to make a strong bridge. Students also had to learn mathematical terms such as area, perimeter, and dimensions. They used these to describe the size and shape of the wood they would use to build their bridge. Finally, they learned about the natural pattern in wood called the grain, and that wood is very weak if it is bent along the length of the grain. Learning these concepts opened their eyes to how challenging the task of building a bridge could be.
The Engineering Design Process
In the Ask and Imagine Stage of the Engineering Design Process, students researched some of the most common bridge types in Taiwan like beam, truss, arch, and suspension bridges. By learning more about the different types of bridges, our student teams were well on their way to making an informed choice of which bridge they wanted to build.
For the Plan Stage, students started getting hands-on with their materials. Those were balsa wood, white glue, and thread. In teams, the students worked together to combine their material list with their chosen bridge design in order to find the exact dimensions of wood for their bridge. To finish this step, they drew a detailed plan for their bridge that included labels and measurements.
In the Create Stage, students gathered the materials they needed, and started to build their bridges according to their plans. Most teams chose to build truss bridges made of strong triangular structures. A few chose to make suspension bridges, which are more challenging to build. Either way, finally getting to build their bridges was an exciting step for our young engineers.
In the Test and Improve Stage, we tested each bridge by adding mass until the bridge collapsed. By testing each bridge until it failed, we could check where the breaks occurred. This let us see what really makes a strong bridge and what doesn’t. Students weren’t upset to see their work break, they were thrilled to improve on their designs. They identified weaknesses and got back to building.
The Building Bridges project is definitely a student favorite. Testing each bridge until destruction provided an unforgettable “wow” moment that they will remember forever. Students had the wonderful opportunity to see the world through a completely new point of view, the eyes of a structural engineer!
Students’ Final Reports
In this project, students were challenged to design and build a bridge that met two key requirements: it needed to span a distance of 40 cm to cross a deep valley with a rushing river below, and it had to support the safe passage of a toy car. After completing the construction process, students were required to present their final scientific reports, detailing their work and findings as follows.
★ Chloe Tsai 蔡依珊 506
The important features of our bridge are the deck, truss pieces, the roof, and the bottom pieces. The deck is the place where the truss pieces stick. The trusses ( 20 pieces of 10cm x 2 cm wood) make the bridge stronger. Truss pieces connect the deck and roof. The bottom pieces can make the bridge stronger by adding layers and having different grains.
To test it, we put the bridge across two tables with a span of 40 cm. Then, we attached a bucket and put rocks in it until the bridge broke. Then Mr. Munday measured the weight.
Our bridge’s dead load was 56.1g, and its breaking load was 7060g. Our roof started to fail first because some trusses didn’t touch the roof, and those parts didn’t stick properly. I learned that we need to put more layers on the roof and the bottom, so it will be stronger. Other teams had the same problem as ours, but theirs broke faster than ours. I would like to change the bottom from 20 small pieces to 4 larger pieces. It could be stronger when all the wood pieces stick together correctly.
★ Yoyo Lin 林芍攸 507
Our truss bridge is made from 3 kinds of wood pieces. The first kind is one long piece that serves as the bridge's deck. Its dimensions are 40cm x 8cm. The second kind are 20 small pieces of wood that serve as the triangular structures holding up the bridge at the middle. Their dimensions are 15cm x 2cm each. The third kind is one piece of 50cm x 8cm wood. It serves as the bridge's bottom part.
We tested our bridge in two steps. First, we tested if a toy car can cross the bridge and measure its dead load. Next, we dangled a bucket on the bridge and added stones until the bridge fell. We measured its breaking load then.
Our bridge fulfilled the toy car test, and when we started to add stones to the bucket, the features on the right structures and deck creaked and bent. Several structures snapped and the right part of the deck broke before it fell. Its dead load was 39.1g and its breaking load was 2875g.
The weakest bridge in class was an arch bridge that hadn't been properly built, so it fell quickly into the bucket. The strongest one was a truss bridge. Its deck was made from connected wood pieces so the deck can take more weight. It was the lightest bridge. If we can build the same type of bridge next time, we will change the two pieces of wood that served as deck and bottom into connected wood pieces.
★ Woody Hsieh 謝宇智 502
The important features of our bridge are the deck, triangles, and top. The deck and top were important because the deck was the place where cars pass, and the top can defend against compression. The triangle parts are also important. In science, the triangle is the strongest shape, so it can stand both compression and tension.
Before the test, the teacher helped all the teams measure their bridges’ dead load weight. During the test, we put our bridge between two tables. The length between the two tables was 40cm. Then the teacher used a line and tied a bucket to the bridge. Then we put sand and rocks in the bucket, so the bridge could carry it until it broke. When it broke, we measured the weight of the bucket to know the breaking load.
Our testing results are: 1. dead load: 34.5g. 2. breaking load: 3725g. 3. The toy car could pass our bridge. 4. The triangles and top wood broke because our triangles didn’t connect deck to the top section.
Our bridge was similar to Team 3's bridge. Their triangles didn’t connect to their top section, either. But our bridge carried more weight than theirs. Theirs only carried 1220g. Team 2 and Team 4’s bridge held more weight than ours, but the toy car couldn’t go through theirs. Our class all build truss bridges. If we can build a new bridge next time, I would like to connect the top and deck with triangles tightly, or the bridge will be very weak. Also, I want to make more triangles so the triangles could carry more weight.
★ Tommy Rhys Leung 梁彧 504
Our important feature is that our bridge has 24 trusses with 12 on each side. Our bridge deck is 48cm x 10cm and the roof is 49cm x 10cm. We only had 1 deck and 1 roof. Our trusses' wood grain is the long way, which much stronger than the side way. When we tested our bridge, we hung a bucket underneath the bridge. Then we started to add sand until we reached the breaking load of the bridge.
The result of our testing shows that our bridge's dead load is 50.8g. The breaking load is 6,705 kg. Our team got second place. There was one team better than us. Their breaking load was 15.16kg is because they had two decks so it could withstand more tensile force. There was another team that cut the trusses wrong, so their bridge's breaking load was 1.670kg. If I could build the same type of bridge again, I would make the deck two layers. This is because it can make the bridge be stronger. I would also glue the trusses nicely on the roof and the deck so it can make it tighter and harder to bend. Last I would add more trusses so they can help the bridge support more weight.
Page updated
Report abuse