Week 5: WPBD vs. KNEX

In the last weeks class, we started to build a truss bridge of our own with the KNEX. Unlike the weeks prior to where we used the WPBD. Both ways a vastly different from each other, one it utilized on the computer and the other is hand made. Therefore calculations on the bridge are alot harder when done by hand. Therefore alot more time consuming, unlike WPBD that would run throught the calculations in a second.

Unlike WPBD with the KNEX we were able to do anything we felt. We were not limited to gusset constrains even though there were other constraints. Also building the bridge by hand gives us a more hands on approach to the actual things physical factors that affect the bridge and its sustainability over time.  Once we get a grasp on the how the bridge can be affected, we can build a stronger bridge. Unlike WPBD that did not tell us how the bridge had uneven weight distribution, we simply just swapped a pipe out to make it stronger, not knowing exactly how it did so. 

In the end both ways are excellent on their own in the process of bridge designing, but with the combination of both, one is able to get a full novel grasp on bridge designing, although it seems for practical for us to learn with the KNEX first to get a grasp, then build with WPBD.

Week 5: WPBD - Knex

During the past weeks, the students have been introduced to two different methods of designing and constructing a truss bridge. Although there are similarities in the two methods, each method demonstrates different aspects of engineering. The West Point Bridge design software allowed the students to comprehend the mechanism involved in designing a truss bridge. Similarly, designing the bridge using Knex provided the students to visualize the structural behavior included in the designing an actual bridge. Along with that, both methods express the budget factor that plays an important role in the designing process.

The major difference between these two methods would be that West Point Bridge Design software has a limit to the types of gussets used to connect membranes while the Knex method limits types of materials and their thickness to construct the bridge. In my perspective, WPBD software is very time efficient and more convenient in regards to restructure and rearrange the design of the bridge calculating the cost of the bridge. The software also allows the students to quickly calculate the cost of the bridge, while the Knex method requires the students to calculate everything using excel file. In addition, the Knex method provides more hands on experience the assembling of the truss bridge. Overall, both methods serve as a great guide to comprehending the engineering aspects convoluted in designing process.

During the previous week in class, we discussed the constraints that need to be considered in building the final design. We also received an overview of the assessment that each bridge will have to undergo during the final week. For the rest of the class, the group decided to work together in designing a “real” truss bridge using Knex. For next week, each group member will have a blueprint of their own unique design including the details of materials involved in the construction.

A2-JACOB

Bill of Materials

Elevation Image

Plan Image

My initial objective was to construct a truss bridge that satisfied all the design constraints and had the best price to weight. I realized that the best way to start the design is by applying what I learned so far. Therefore, my objective shifted to building the simplest design with smallest membranes that followed the same truss pattern as the one I designed on the WPBD software. To build 8" wide flat portion on the top of the bridge, I decided to remove the arc that I previously designed on the software. My initial designed consisted of blue and white long chords because I recognized that shorter beams are more stable than longer beams. My initial design of the bridge was expensive and totaled over $350,000.   During the designing process, I was able to cut down the price significantly. I recognized that one yellow long chord going diagonal was efficient and cheaper than having two white chords connected with a gusset plate going diagonal. By replacing the white chords with one yellow chord enabled me to lower my price range to $277,500. The basic outline of the bridge didn’t experience any change and remained as a trapezoid with the long base that spanned 2 feet and 1/8 inches with a height of 3.125 inches. This assignment was a great learning experience as well as a great hands-on experience on how real designing work. The assignment also taught me the importance of making accurate measurements and keeping a record of the progress of the design. Overall, this assignment was a great way to understand the engineering aspects involved in designing a bridge.

Week 5: WPBD - Knex

After Transitioning from WPBD and into Knex for designing a bridge, I realized that WPBD is much easier and different than Knex. In WPBD we did not have to face problem with dimensions or the materiel size. Students were allowed to create beams from any point to another point and than allowed to just test the bridge to observe the results. With Knex we only have few options to choose from to bulid our bridge and also have to take in considerastion which part fits with other parts. For example, depending on the outer frame of the bridge, only a certain bars or design can be used to create the 'web'. In the Knex's kit we have to choose from the different collored beams accoriding to size, such as white, blue, yellow, red, and gray; in addition with the types of gussets. The main difference between WPBD and Knex is the lack of helpful feed back WPBD provided on the tension and concentration or each material.Both West Point Bridge Design and Knex are excellent tools for engineers to understand how professionals design real structures. It is a tool that helps visualize structural behavior and also an opportunity to experience the design process.
  
Last week in lab we were introduced to Knex and allowed to play with them get a good understanding. The first thing done was a presentation which gave details and constrains for the bridge competition. I was able to realize what my bridge needs to accomplish and how it should be design to meet the constraints of the competition. Furthermore, the presentation informed the class about the different Knex parts and how much each will cost. At end we were allows to play with the Knex to get a good feel of how the bridge will be. This week in lab we will work more with the Knex pieces and attempt to Build a bridge for the competition.

A2 - Parth Patel

 

 My idea for designing the bridge is to use small pieces, such as the blue and white beams, so that I can  include more numbers of pieces for a low estimated total cost. My design contains square cross sections, which holds triangular webs to provide the strongest support. Design 1 contains a strong web, but is a expensive bridge while Design 2 has weak webs for a low cost. During the designing process, I changed various aspects of the bridge, such as making the bridge smaller by using the blue bars instead of yellow bars for the outside frame. In addition, I changed the design of the web several times in order to create a very inexpensive bridge. In conclusion, I was able to receive experience on how to use the Knex pieces to design a bridge. It was a very good experience because it was much different than using West Point Bridge Design and required more critical thinking. In addition, I learned how to design a bridge by keeping the cost in consideration, which will be of huge importance during the competition.