A2 - Jiang

     The idea of my bridge's shape is from the results of West Point Bridge Design I tried last week. During several times of experimentations, I found that it was much easier to make a bridge for doing bottom and top truss at a same bridge. I tried to do only bottom truss, like Deck Truss. However, the bridge always collapsed when the truck was passing. And the bridge even cost me more money when I finally made it without top truss because I have to add more web members to make the bridge be stable.  My original design, which has both of bottom and top truss, its strength and tension were evenly distributed by the short chords I added on the top. 

side view

top view

Bill of Materials - K'Nex pieces

Height: 5.875"

Length: 27.028"

     I used colors to differentiate the various chords I added. The yellow chord is 3.375" long; the red chord is 5" long; the black chord is 1.25" long.

    About the gusset plates, I used three types of those plates. Two of 360' gusset groove plates could connect the top and bottom truss in the middle. And when I thrusted a 90' gusset plate into a 180' gusset groove plate, the mixture gusset could connect the rest of members. 

About changes

      At first, I tried to make a bridge with arch. But end up with failing. May be because the arch bridge can not be done with K'Nex pieces.  So I started to make a K truss bridge and I thought that it shortened the lengths of the compression members compared to the other trusses. The thing I changes of K truss was I added two short chord under the middle K truss. ( like the picture shows below) 

 The reason why I did that is because this two black chords could support the top better. 

What I learned from K'Nex is the material I chose can limit my idea of bridge design. But I also also learned how to those prescriptive chords and gusset plates to build different shapes of truss bridges. 

- Yilei Jiang