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Civil Engineering + Environmental Engineering: Bridge and Windmill Design
Civil engineering focuses on designing and building structures like bridges, towers, and support systems that can safely carry loads. Environmental engineering applies engineering principles to energy, sustainability, and natural systems, creating solutions that work with the environment. Together, these two fields connect in projects like our bridge and windmill designs. The bridge demonstrates civil engineering through truss systems, load distribution, and structural reinforcement. The windmill highlights environmental engineering by capturing wind energy efficiently with blades and supports. By combining structural design with renewable energy concepts, both projects show how civil and environmental engineering work side by side to create strong, sustainable solutions.
WINDMILL
We first completed a full prep activity focused on testing how different design choices affect lifting power. Using K’NEX connectors and rods, index‑card blades, balsa‑wood reinforcements, string, a paper cup, and hex nuts, we built a working windmill structure and ran controlled tests with a box fan. We experimented with different variables to measure how each variable changed torque, speed, and the amount of weight the windmill could lift.
For the windmill project, we used Onshape to design a scaled‑down prototype of the tower and blade system. The model was detailed but rough, meant to capture the overall structure rather than exact dimensions. We exported the design and 3D‑printed it, creating a physical prototype that gave us a clear visualization of how the windmill design could look and function.
Our windmill design began with the idea of using long blades and a tall structure to maximize stability and capture more wind. At first, this seemed like the best way to generate power, but testing revealed that the long blades had too much inertia. Because of their weight and size, they struggled to spin efficiently when exposed to the fan.
To solve this, we redesigned the windmill with shorter blades, which reduced inertia and allowed the system to rotate more smoothly. We also corrected an orientation issue caused by both blades being connected to the same dowel, which had prevented them from spinning freely. Once these adjustments were made, the windmill became lighter, faster, and far more effective.
This process showed how small design changes, like blade length and orientation, can make a big difference in performance. By iterating and refining, we transformed our original concept into a windmill that worked consistently and efficiently.
The final windmill has a tall, sturdy frame built from balsa wood with cross‑braced supports on all sides. The structure is tall and balanced, designed to keep the tower stable while the blades spin smoothly. The top section holds the axle and blades securely, allowing consistent rotation during testing. The finished design shows how careful alignment and strong framing can make a lightweight windmill steady and efficient.
The windmill spun very efficiently and consistently lit up the light in the back, keeping it on without interruption. Overall, it worked extremely well and showed strong performance in testing.
IMG_1912.MOVBRIDGE
Before building the final balsa‑wood bridge, we completed a series of prep activities using index cards. These mini‑builds helped us understand load, compression, tension, and how different structural shapes affect strength. We tested different supports and structural design ideas to see how each design changed the number of hex nuts the structure could hold. This activity then helped us choose the strongest, most efficient design for our final build.
For bridge project, we used Onshape to turn our structural ideas into precise 3D models. We roughly made a prototype of how our bridge would look like, letting us check symmetry, fit, and load‑path geometry before building. Once the model was finalized, we exported it for 3D printing, creating an accurate physical prototype that matched the digital design.
We began by using Bridge Designer to test different bridge and support systems to see which would hold the most load. After selecting a design, we drew a rough diagram on the whiteboard, carefully calculating all side lengths and member lengths to make construction easier.
When it came time to build, we realized we didn’t have enough time to complete our original design (shown in the 3D print). To adapt, we cut out the bottom half, reinforced the legs, and added more supports underneath and along the sides of the bridge. We also grouped four thin balsa wood sticks together to create stronger members that could handle greater loads.
Throughout the process, we identified every weak spot and made sure our truss system was structurally effective. These adjustments gave us a bridge that was both efficient and capable of holding weight reliably.
The finished bridge has a clean, symmetrical truss on both sides. It is around 4ft wide and 2 feet tall. Each side mirrors the other, which helps balance the load evenly. The legs are reinforced and extra supports run underneath and along the sides, giving the structure more stability. We bundled thin balsa sticks into groups of four to make stronger members, which kept the bridge from bending under weight. The result is a lightweight but sturdy bridge that looks neat and holds heavy loads with ease.
The bridge easily held 21 bricks, and it could have supported more if the stack of bricks hadn’t toppled, breaking part of the side. Even after that, the bridge still held two people standing on the legs of the bridge (see picture), showing how strong and stable the final design was overall.
IMG_1934.MOVResearch Papers
Simulations and Models Research Paper:
Air Pollution Research Paper:
https://docs.google.com/document/d/1309yY6kx8JIEBQluLeugaDyFDlkwl1ySeaOzv5HXNno/edit?usp=sharing
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