Read the Following Selection
Read the following selection, or click on the play button below to listen aloud.
Four Types of Bridges
In the diagrams below, the pairs of arrows show the following forces at work:
<– –> tension –> <– compression
A beam bridge has a horizontal beam supported by two piers. The beam bends when a load is on the bridge. A load can be cars, trucks, or a train. Compression acts on the top side of the beam and the two piers. Tension acts on the bottom side of the beam.
The arch is a very strong shape. A load on top of the bridge causes compression on the top of the arch. It also causes tension at the bottom of the arch. This tension could cause the arch to spread apart, making it weaker. The material on the sides of the arch acts like buttresses. The material keeps the arch from spreading apart.
A truss bridge is built with triangles made of steel bars.
A triangle is a very strong shape. Compression and tension forces act on the bridge. The diagram below shows the forces.
On a suspension bridge, tall towers support the main cable. Smaller cables attached to the main cable support the roadway. These cables are called suspenders. The main cable is attached to large blocks at each end of the bridge. The load of traffic on the bridge is transferred to the suspenders. This causes tension in the suspenders. The suspenders transfer the load to the main cable. This causes tension in the cables. Compression acts on the towers as they support the weight of the bridge and the traffic.
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1. Match the definition to its term.
- has a horizontal beam supported by two piers
- built with triangles made of steel bars
- has tall towers that support the main cable
- a load on top of the bridge causes compression and tension, material on the sides act like buttresses
2. Snow and ice can build up on the roadway of a bridge, making it heavier. Are snow and ice internal or external forces?CorrectIncorrect
3.A simple beam bridge can be built over a stream. All you need are two blocks and a wooden plank.
What force acts on the blocks when someone is crossing the bridge?CorrectIncorrect
4. For the same scenario as Question 3, what force (or forces) will act on the top of the plank?CorrectIncorrect
5. Is the weight of the plank an internal or external force?CorrectIncorrect
6. You are designing a bridge that will take tour buses to an interesting place. Explain why you would need to know the following information:
The maximum number of people that can fit in one bus.
Great answer!Great answer!
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