A1- Ye

Design goal:

In the circumstances that ensure the safety use of the bridge, decrease the budget of the bridge as much as possible. According to the result of my research, when the height of the bridge is approximate one sixth of the length of the bridge, it could bear more weight. One sixth of the 44m, the fixed length of the bridge, is 7.3m. According to the circulation result, the 7.3m would be the perfect height.  At the same time, the length of the interval between fixed junctions on the surface of the bridge is 4m. The equal literal triangle would reach the most stable balance. The compromising of these two facts, a double-decker bridge would be an ideal option.  

Design constraint:

There are several constraints for the bridge design. First, the number of joint on the surface of the bridge is fixed. Second, the using of the cable and the intermediate support are forbidden. Third, the available time of the design is limited.

The cost of the design: $301726.57

2-D image of bridge design

Truck in the middle of the bridge

The result of Load test

How my bridge changed during the design

Design Version 1

Design Version 2

The cost of the design version 1 is $509902. The cost of the design version 2 is $486612. All of these three version could satisfied the safe requirement. But the evolution from version 1 to version 3 took a long time. I did the comparison between three different basic combinations of the triangle which are Howe, Pratt, and Warren.  I did the comparison between hollow tube and solid bar. I did the comparison between different member types with different thickness. If some members were bearing less force, I would reduce the thickness of it. And if some members were bearing too much load, and I  would increase the thickness. 

The money issue

The current cost of the bridge is  $301726.57 . It is the result of many hours of testing and research. There are still some room for the improvement by adjusting the thickness of the membrane. And in the future, theoretical research of truss bridge and detail force analysis would greatly help to improve the bridge. My goal is control the budget under $300000. 

What I learned from the bridge

 Before I built the bridge, I thought design is coming from instantaneous inspiration. But after I have faced more than thirty times of collapse of the bridge, I realized that design is about patient and courage. Being patient to redo the bridge, and the courage of erase the original design are critical in this assignment . I need to use my ability of reasoning and analysis to find out the negative part of my old design and invent a new one.