Daming Gao
Engineering Design Portfolio
CIV102: Pedestrain Bridge Design
In our course (Structures and Materials), one of the biggest project was to design a pedestrain bridge which fulfills the following requirements:
(1) The 150m long bridge spans over a river, which is about 50m wide. No column can be placed into the river.
(2) The bottom of the bridge must be 6m above the river.
(3) The average weight of the bridge should be 0.7KN per square metre (within 15% is acceptable)
Figure 1: The engineering drawing of our final design.
Figure 2 (above): The Corresponding Design Phases
First, we received the problem statement from teaching team. Then, we started to brainstorm the geometry of the bridge. We prioritized aesthetics as a more important criterion, but after some simple calculation we realized that this process would be extremely tedious and might require advanced mathematics, which was beyond our capabilities. (Feedback) As a result, we simplified our design (Figure 3)
For the truss in Figure 3, we found it much easier to calculate. However, a new problem was emerged. Normally the members in the "web" (i.e. vertical and diagonal members) next to each other should carry different types of forces (compression or tension), but in this case, some of them next to each other only carried tension, therefore a weak spot was created. If a force is applied there, those members will fall down. As a result, we modified our design (Figure 4), and changed the orientation of some members. The problem was solved.
Figure 3: A new design that is much easier to perform calculations
Figure 4:
A modified design which ensures all the web members next to each other have different types of forces (namely, tension or compression). Notice the orientations of some members are changed (the black line is the original orientation, the red line is the new orientation.
2013/10