Week 3: Structures

Civil Engineering

Civil Engineering is the design, construction and study of infrastructures such as, buildings, bridges and roads as well as water resources. They are the people who makes these things as safe as possible and as efficient as possible. They think about the transportation of water, electricity, people and other goods from place to place. 

Building Science

Building science is the study that helps better the indoor environment quality.   It integrates knowledge from various  fields of studies such as physics, chemistry, engineering, architecture, and environmental science to understand how buildings interact with the environment and how they can be designed, constructed, and maintained to improve performance, 

Bridge Designer

Through Truss - Pratt Bridge

Truck Load Simulation

Our efficient bridge design minimizes the cost and still allows the truck to cross comfortably. This is a good bare minimum cost design that can be modified to lessen the stress on the members. This marks the lowest budget 

IMG_5132.MOV

Test Results

This table shows every member the bridge is composed of. The members vary in size, slenderness, length, and cross section. These different factors were all optimized for cost reduction and effectiveness. Because of its low cost, some of the members are pushed to its limits by compressive and tensile forces. For example, member 9's compression force is at 0.97 which is almost at its breaking point (1). The member resisting the most tensile force is member 23 at 0.94. This table provides various important information to consider when trying to build a functional and cost effective bridge.

Cost Calculations

The cost calculations report shows all the members, their thickness, their respective cost per product, and other costs for construction. For maximum cost reduction and efficiency, we varied the members on the bridge. One method we used to reduce cost was to make the less crucial members thinner. Another method was to use tubes instead of solid steel bars when possible. Hollow bars require a lot less material and is therefore much cheaper. However, a hollow tube trades strength for a cheaper cost. Tubes are much cheaper but are a lot weaker so they have to be thicker to withstand the same stress. In some situations, a thicker hollow tube may be cheaper than a thinner solid bar. After many trials, fails, and revisions, we managed to design a functional bridge at only $214,000.

Model Smart 3D

The ModelSmart3D model was the first concept of the Truss Bridge. Since there are many types of Truss bridges, we all reviewed the different styles and ended up choosing the Pratt Truss Bridge. 

Tinkercad 3D Model

This is the final design of the Truss Bridge. As you can see, we decrease the number of Trusses and added pears to support the weight of the bridge. We decreased the number of Trusses because we needed the Truss to be higher meaning the number of truss itself had to be smaller to make each individual truss bigger.
https://www.tinkercad.com/things/jTJTe4IV0pZ-terrific-turing/edit?sharecode=uteUYNouyEbuWNRVqnY41Yjg0zKElRxyHM2TXA7TYeE

Constructing the Bridge

Truss

We encountered many issues with the construction of the truss. Firstly, we miscalculated the length of the board itself and we made it 3 foot long when we had to make it 4 foot long. At this point we were running out of boards as well so we used a combination of the straws and a few boards structure to replicate what we were doing previously. Also because of human error and our messiness with cutting the straws to the calculated size, the straws were in different length making one side of the truss longer than the other.  

Pier

As mentioned before we were running out of boards so we had to be creative with how we used them.  We first cut 36. by 3in. boards into 3, 12x3 in. strips. The X shaped pier is composed of two of these strips. To create the X shape, we cut one of the strips in half vertically and then glued them on either side of another board.  The piers were very sturdy and did not buckle under the compression of the brick cart going over it during the test.

The Bridge

By combining the 3 components, the truss, 4 piers, and the base, we were able to create a complete Pratt bridge. The bridge seemed promising but our estimation of how many bricks it can hold was about 4 bricks. We added some additional gussets at crucial joints to create a more stable and strong connection.

Photo of Paper truss Bridge

Testing of the Bridge

IMG_4164.MOV

Bridge Test

The bridge actually held up better than any one of us expected. The bridge was able to hold 6 bricks until the truss at the end split. 

Research Paper

Group #11 Week 3 Reasearch Paper