Week 2

Bridge Building

Civil Engineering

Civil Engineering is an area of engineering that dedicates itself to manipulating the natural environment around an area to benefit people living locally. This typically means building infrastructures such as bridges, roads, and other transportation networks.

Building Science

Building Science is the study of how physical forces can affect architecture in order to extend the building's sustainability. In the context of bridge building, Building Science would consider the effects of rain and wind on the strength of the bridge.

How Do They Interact?

While Civil Science is necessary to keep a city functioning, the infrastructure that it leaves behind is prone to damage from natural and human causes. For example, a bridge is susceptible to car vibrations, winds, and hits from waves. Building Science serves to lessen those impacts and increase the operating time of Civil Science Projects.

Design Process

The design process is as follows:

Use a bridge-building kit and simulations to understand the strength and workings of a truss bridge.
Design a balsa wood bridge through software
- Test the bridge within the software and make changes accordingly
3D print a miniature model of the balsa wood bridge
Build the balsa wood bridge according to software designs

Bridge Kit

This is a model bridge built by John and Harry. It was mainly built from paper and is strong enough to hold several metal nuts. It uses a standard straight truss design.

Simulation Practice

This is our solution to the bridge-building simulation problem. We successfully met the criteria:

The truck can ride safely
Cost-Efficient/Cheap
Members have:
- Tensile Strength less than 0.45
- Compression Strength less than 0.4
15% of tubes must be hollow

We had a significant challenge with pricing, causing us to meticulously consider spacing and hollowness for every member. We brought the price down to 279 in the time that we had.

Net Forces on All Joints of the Simulation

Modeling Through Design Software

We used Bridge Designer 2016 to make a design for the bridge, and ModelSmart3d to model it in 3D and manage our materials.

First Design

The first design was a flat truss bridge. However, it was scrapped because testing revealed that there were large displacements at certain joints of the bridge, and it was unable to hold a sufficient amount of weight.

Second Design

Pictured is the second design, which features an arch truss design that has no such displacement problems and is able to carry more weight at around the same cost. Beams on the floor were put in x-patterns. There were wide variations in widths for the member pieces.

Final Design

The third and final design shares the same arch design as the second. The main improvement was narrowing down the variations in widths of the wooden beams. In addition, the x-patterns that covered the floor of the bridge were removed as they were deemed unnecessary. We also made the bridge twice as wide because we realized that our bridge was not wide enough for bricks to fit on it.

3D Printing

The next step was to 3D print the bridge design. We modeled the design to be printed in TinkerCad3D. It seemed that the top of the arch was too flat, causing the filament to spiral out of control. Aside from that, the bridge printed smoothly.

Building

We built the bridge design out of balsa wood. The initial problem that we had run into was a 1/2 inch decrease in length on the first side. This was due to the inaccuracy of the cuts when cutting out the members. The small inaccuracies added up and created a noticeable difference in length.

The next challenge was matching the other side of the balsawood bridge to the same decreased length as the first side. This was difficult mainly because we had precut everything beforehand.

Finished Bridge

Final Bridge Test

FAQ

Research Paper

Week 2 - Bridge Building

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