A3 - Staquet

For assignment three I analyzed the given truss design using the "Method of Joints;" the process to find the force running through each member of a truss based off of the joints that connect it.  My calculations can be seen below in Figure 1.

Figure 1.

With the above calculated forces I was able to draw a diagram of the bridge showing the force on each individual member.  This can be seen in Figure 2 and please note that these forces are in pounds.

Figure 2.

Next I used the online Bridge Designer to further replicate my analysis.  Figure 3 shows the analysis done on the same bridge as seen earlier though the forces are slightly off.  I would have to say that this minimal error is due to the Bridge Designer having a poor grid system with no labeled increments and the use of the mouse arrow/pointer to place the nodes rather than a cross hair or x.  Another problem was the fact that my bridge was 36" long and 10" tall, causing its triangles to have irregular angles and making it slightly tougher to scale than a bridge made of 45, 45, 90 triangles.  Non the less, with the right scaling and proportionality I was able to get most of the figures correct by hand and the figures that didn't match up were only about a half a pound off.

Figure 3.

I have also included the analysis, done with the online Bridge Designer, of the group bridge that was built out of K'Nex.  We completed this as a group and a screenshot is provided in Figure 4.

Figure 4.

This type of analysis can be useful in improving our K'Nex bridges because it gives a great visual of which pieces are undergoing compression forces and which are experiencing tension forces.  The numbers associated to the forces can be loosely used as a reference due to the change in design for the 36" bridge as well as how the force acts on the K'Nex during testing.  The K'Nex bridge does not experience a force on its underside, nor is it applied at a single joint.  Overall, the "Method of Joints" is a useful tool in the design of a bridge or any structure composed of joints that will be undergoing forces.