A3- Truss Analysis: Breslin

To determine the forcing acting on the member of a bridge, the Method of Joints was used. In this example the height is 6 inches, the length was 24 inches and the weight of the load is 10 pounds.

Below is a diagram of the diagram of the simple Truss Bridge with a table of the Member to Member forces.

After completing the analysis of the simple truss bridge by hand, a program called Bridge Designer was used. This program allowed the computer to determine the areas of tension and compression in the bridge.   The figure below is the result of the simple truss bridge in Bridge Designer. The red lines represent tension and the blue lines represent compression.

The results of the hand analysis match the results of the Bridge Designer analysis. When recreating the analysis in the Bridge Designer, it is important to make sure that the bridge is to scale. The bridge in the computer program must have the same dimensions in order to calculate the correct forces and produce the same results as the hand analysis. If the two do not match up then the bridge has not been scaled the proper way.

In the Bridge Designer program, there are specific constraints in the program which does not allow the proper analysis of the Knex Bridge. The program does not allow for the correct representation of the bridge structure. Without all of the members of the bridge being represented properly, the forces of the bridge in the program do not correspond with the forces in the actual bridge. Another important factor when calculating the forces on the Knex Bridge is to use proper scaling. Whether hand analyzing or computer analyzing, scaling is important to determine the correct forces.

The testing information about Knex joints can be extremely helpful when analyzing the bridge. By using the average strength of each joint in the bridge, one can use the Method of Joints analysis to determine how strong the bridge design is and then find ways to strengthen the regions of the bridge that are weakest. This type of analysis can help one to understand the mechanics of the bridge design and know how and where to improve the structure.