Week 7: Analysis Desires

One of the differences between WPBD software and Knex is the “Block box” answers. The “Block Box” provided with values associating with compression and tension of each membrane of the bridge design. These numeric values were very useful in terms of studying and understanding the strength and weakness in the design of the bridge. In addition, the software highlights the membranes that failed the bridge after each load testing. These were great beneficial features because it allowed us to analyze our bridge design effectively. As a result we were able to construct a serviceable bridge design that satisfied all the constraints and remained in low budget. Working with Knex would be more resourceful if there was a system to calculate the tension and compression of each membrane as it goes through the load testing. I would recommend using the VideoPoint software which can be used to record the testing and analyze the footage. VideoPoint with VideoPoint Capture allows you to gather position vs. time data of a QuickTime movie. The collected data can be viewed in a table and plotted to examine the design of the bridge.

During the previous week in class, our group was able to make little modification to the original bridge. While we modified our bridge, we were quickly able to come to a hypothesis that our grooved gusset plates and the long chord were worn-out from constant remodeling. From the testing we were able to conclude that our bridge design was very weak because it was only able to hold about 5 pounds. During the class discussion we were very interested by one of the groups who decided to design a bridge without any grooved gusset plates and produce good results. Therefore, we decided to redesign the bridge by completely replacing the grooved gusset plates with other connectors. This week in lab we will conducting more truss analysis and learning about the joint method and the importance of free body diagram.

Week 7 - Analysis Desires

West Point Bridge Design provided very useful feedback such as the tension force and compression force for every beam and gusset point. The numeric information helped students understand their bridges better; areas that are over strained or less strained. With this resource I was able to change the design around and try different methods to find the lowest cost to strength ratio. Unfortunately, Knex does not provide numeric feedback but allows student to visually see how the bridge fails. This allows students to observe the effects of different weights and points of the bridge where it collapses. However, with numeric information for the amounts of forces applied at various points of the bridge could help me understand better how the bridge fails. For example, if the tension on a certain beam is high, I would change the design on that area to prevent it from collapsing. Vise verse, if the tension on a certain beam is very low, I would try to parts out from that area so it can reduce the total estimated cost. Unfortunately, I have no previous idea or research for how to calculate these numeric values.   

Last week in lab we had spent a long period of time testing the bridges created by all the groups. My groups bridge resulted in a epic failure. It was completely unstable, unreliable, and only held a little over 5 pounds. My group had already anticipated a bad result before the test because we recently realized that the 180 groove gusset plates are extremely unreliable to use as connectors. The two combination of two 180 grooved gusset, which was used numerous times in our design, easily separated even without a lot of weight compressed on it. Unfortunately we didn’t have enough time to change our design and had to face the failure. However, my group has acquired significant knowledge from the failure to be able to build a better bridge. This week in lab we will learn how to analyze bridges and calculate numeric values, which will also help to design a stronger bridge for the week 8 test.