Bridge Project
Task 1: Bridge Kit
Diagonal View
Birds-Eye View
Task 2: Bridge Designer Bridge
Pratt Truss Bridge Side-View
Using the template based off of the TA's presentations, this default bridge design was created. It takes advantage of the triangles strong characteristics discovered by the group through discovery in the bridge kit.
Component/Member Breakdown
To the left is a list of members used in the construction of the bridge structure. The design requirements dictate between 14-16% of hollow components which has been observed as evident in the list. In addition, the outlines and regulations for the maximum compression force and tension force respectively are also followed with neither the compression force nor the tension force exceeding 0.41 and 0.46 respectively. Upon closer observation, one can also conclude that the dimensions of individual members have been altered and there is no uniform thickness across the board. This is because, in order to minimize cost and simultaneously ensure structural rigidity, multiple load tests were done and individual members we manipulated.
Cost Breakdown
As mentioned, the lengths and dimensions of the members of the bridge were manipulated to minimize cost and meet the design requirements on blackboard and the syllabus.
Total Tensile and Compressive Forces on Bridge Components
The total compression and tension forces summed up in a simple excel sheet.
Net Forces on Individual Nodes based off Member Net Forces
Using the cosine trigonometric ratio, our team was able to combine the net of the forces on members of the bridge to determine the net forces on nodes/vertices. This was achieved by considering forces as the vectors they are and canceling and combining certain magnitudes of forces. The resultant forces are shown below and they sum to a total of 24476.83.
IMG_1648.MOVTest Video
The bridge passed truck's while supporting its own weight along with the weight of the additional load based off of the determination of the computer load test.
The Math Behind The Bridge
Members that had net forces acting on multiples of 90 were easiest to combine as due to the sign convention it was simple to deduce that left and down denoted negative while up and right are positive. Due to the design of the truss bridge, angled vectors were also easy applications of trigonometric ratios. In our case, the bridge was made of right triangles to more universal formulas/rules like the cosine or sine rule weren't necessary/used. The simple right-angle triangle had a square design so the angle distribution is 90, 45, and 45. This means that the vertical and horizontal components of a member that acts as a hypothetical hypotenuse are the same. Combining the x and y components and summing the squares and rooting the sum gave us the answers for net forces acting on the individual nodes which we labeled A through P and summed to get the total net force.
Task 3: ModelSmart3D for Load
This is the bridge design from ModelSmart3D. Originally, there was another bridge but the data for it was lost. So instead, we rebuilt and made a better design. In the left hand corner, in the image next to this text, is >>>> It Worked! <<<< . Also featured on task three, are different angles of the bridge and a hand drawn scaled model of the bridge.
Scaled Drawing
Task 4: TinkerCAD for Printing
TinkerCAD Bridge
According to the dimensions and design constraints described in the syllabus, we created a design on TinkerCAD. The standard Truss bridge concept is repeated in this design except the supports are extended on either end.
Scale Drawing
Our team used hand drawing to create a scaled representation of our bridge design. This allows us to have a reference point from different viewing angles when assembling the bridge.
Task 5: Physical Bridge (Construction + Final Product)
When the bridge was finished it was placed on a shake table and bricks were stacked on top of it, this was the testing phase of our physical bridge to see what it could handle. When our bridge was tested it was almost able to hold the maximum number of bricks, which was 20. Our bridge was able to hold 19 bricks before failure, but our bridge was not completely destroyed and can still prove useful by allowing us to more easily identify the point of failure.
