In this case, I was tasked to analyze a truss system. The main focus of this analysis was to inform a general contractor whether a model for a particular bridge was oversimplified. The contractor was worried that the model for the bridge was oversimplified because it neglected the member weight. In the first part of the problem I was required to analyze the structure by neglecting the member weights, but adding a simulated truck load on the bridge. In the second portion of the problem, I removed the truck weight and analyzed the bridge using the actual member weights. In my problem, the member weights were 850 lbs a piece and they were each 17 feet long.
2. Assumptions:.
The first step I had to take to analyze this bridge was to make a few initial assumptions. First, I assumed that the truss was loaded only at the joints. I also assumed that the members were joined by frictionless pins. In the first part of the problem, I also had to assume that the member weights were negligible. I also assumed that the load (P) was all at joint E. For the second portion of the problem, I assumed that there was no additional load (truck weight) added to the bridge. .
3. General Approach:.
I approached this problem as any great engineer would, by first drawing a free body diagram. I did this for both parts of the problem. In the first part, I neglected member weight and in the second part, considered only member weight. I also labeled all external and reaction forces on my free body diagrams. After this, I used the equilibrium equations to solve for the unknown reaction forces (see appendices A and B). I then broke the bridge into pieces to analyze the forces on each individual member. From this, I came up with my general equations for both parts of the problem. I then used Quattro Pro to analyze my data and created graphs of my data (see appendices C and D).
4. Results:.
Part 1:.
For part one, I solved for the member forces in terms of a simulated load (P) on the bridge (appendix A).