Engineering: Civil and Structural (Middle School) Worksheet

Question 1

A small pedestrian bridge must support its own weight, people walking across it, and occasional strong winds. Identify each of these as a dead load, live load, or environmental load.

Accepted Answer

The bridge's own weight is a dead load because it is always there. The people walking across it are a live load because they change over time. The wind is an environmental load because it comes from conditions in the environment.

Question 2

A beam rests on two supports and holds a 60-newton load in the middle. If the load is shared equally by the two supports, how much upward force does each support provide?

Accepted Answer

Each support provides 30 newtons of upward force because 60 newtons divided equally between 2 supports is 30 newtons per support.

Question 3

Explain why triangles are often used in bridge trusses and roof frames.

Accepted Answer

Triangles are often used because a triangle is a rigid shape that does not easily change shape when forces push or pull on it. This helps trusses and roof frames stay strong and stable.

Question 4

A student builds two towers from the same number of craft sticks. Tower A has a wide base, and Tower B has a narrow base. Which tower is likely to be more stable, and why?

Accepted Answer

Tower A is likely to be more stable because a wide base makes it harder for the tower to tip over. The center of mass can move farther before it passes outside the base.

Question 5

A concrete sidewalk expands slightly on a hot day. Engineers often place small gaps between sidewalk sections. What problem do these expansion joints help prevent?

Accepted Answer

Expansion joints help prevent cracking or buckling. They give the concrete room to expand when it gets warm and contract when it cools.

Question 6

A bridge deck is 24 meters long. Engineers plan to place support posts every 6 meters, including at both ends. How many support posts are needed?

Accepted Answer

Five support posts are needed. The posts are at 0 meters, 6 meters, 12 meters, 18 meters, and 24 meters.

Question 7

Name one advantage and one disadvantage of using steel instead of wood for a large bridge.

Accepted Answer

One advantage of steel is that it is very strong and can support heavy loads over long spans. One disadvantage is that steel can be expensive and may rust if it is not protected.

Question 8

A rectangular frame is wobbly until a diagonal brace is added from one corner to the opposite corner. Explain how the diagonal brace improves the frame.

Accepted Answer

The diagonal brace divides the rectangle into triangles. This makes the frame more rigid and helps it resist changing shape when forces act on it.

Question 9

During a site investigation, engineers find soft, wet soil where a building is planned. Why is this a concern for the foundation?

Accepted Answer

Soft, wet soil is a concern because it may compress, shift, or settle under the weight of the building. A weak foundation can cause cracks, tilting, or uneven floors.

Question 10

A model bridge can safely hold 12 kilograms before it fails. The required safety factor is 3. What is the greatest load the bridge should be allowed to carry during normal use?

Accepted Answer

The bridge should be allowed to carry 4 kilograms during normal use. This is because 12 kilograms divided by a safety factor of 3 equals 4 kilograms.

Question 11

List two types of infrastructure that civil engineers help design, and describe the purpose of each.

Accepted Answer

Civil engineers help design roads, which allow people and goods to travel safely. They also help design water systems, which move clean water to homes and remove wastewater.

Question 12

A cantilever is a beam supported at only one end, like a diving board. Where would the beam experience the most stress: near the fixed support or near the free end? Explain your answer.

Accepted Answer

The beam would experience the most stress near the fixed support. The support must resist the bending caused by the load and the length of the beam sticking out.

Question 13

A city wants a new bridge that is low cost, safe, attractive, and quick to build. Explain why engineers may not be able to maximize all four goals at the same time.

Accepted Answer

Engineers may not be able to maximize all four goals because design choices involve tradeoffs. For example, the safest or most attractive design may cost more or take longer to build.

Question 14

Look at a simple arch bridge. Explain how an arch helps carry loads compared with a flat beam.

Accepted Answer

An arch helps carry loads by spreading forces outward and downward toward the supports. This shape can reduce bending in the bridge and make good use of materials that are strong in compression.

Question 15

A team tests a model tower. It fails when a side joint pulls apart. What is one design change the team could make, and how should they test whether it worked?

Accepted Answer

The team could reinforce the joint with extra bracing, stronger glue, or a gusset plate. They should rebuild or repair the tower, apply the same type of load again, and compare the new failure load with the original result.

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Engineering: Civil and Structural (Middle School)

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