A2- McSorley

1.) The design of my bridge is a straight Truss bridge with triangles used throughout the design of the whole bridge. I decided to use this flat bridge design because I knew the loading apparatus needed to have an 8" flat surface to sit on and I wanted to keep the cost at its minimal. Instead of making the bridge sturdier by adding supports on the top or the bottom, I will use the money to make sure my bridge is very sturdy in its body.

2.) Elevation View:

3.) Plan View:

4.)

5.) During design, my bridge changed in that it is a lot smaller than I would have thought in the beginning. This is due to the cost of the bridge, adding all the pieces made the cost sky rocket, so I decided to try "less is best".

6.) I learned that in the end, the hardest this about making a bridge is keeping the cost reasonable. This is what my team mates and I struggled with the most this week when trying to find the best design.

Week 5 Assignment: WPBD vs. Knex

During this week, we got our first glimpse at a model bridge made of Knex like those that we will be building in the coming weeks. The design was made by an expert in the Civil, and Architectural field so it was pretty much a model of what the best bridge we could build looked like. We went on to watch a presentation given by Mr. Jay Bhatt (the research librarian) about all the possibilities we have not only at the library, but also on the Drexel library website to research bridge design and construction. During this week our team was given a task to create individual bridge designs on paper so that when we come to class during week 5, we are able to grab Knex and make our bridge. We will find the pros and cons of each group member’s bridge and come up with the best design. This is the design that we will use for our group bridge design in the final competition.

            This week we will be working solely with Knex in class, transitioning from West Point Bridge Design. They differ in that when using Knex we can feel it in our hands and test the strength and tension and compression by bending it and testing it ourselves. We can find where the mistakes are and make repairs by hand using different pieces. We have already discovered (from last class, just by playing around with the pieces) that repairs in real life with the Knex are much more difficult to make than on WPBD. If we must make a repair we have to take it apart and change the pieces, sometimes rebuilding the whole bridge. Overall, building a bridge using Knex will be more of a challenge than the West Point Bridge Designer.

Kelsey McSorley

Week 5: Comparison

This past week, the Engineering librarian, Jay Bhatt came in to teach the class about how to use the library and research tools to find questions we would have about bridges. He went over the website and also how to contact him. We also spent a larger portion of the class experimenting with the Knex. Chelsea, Kelsey and I all spent time experimenting with connections and making separate bridges. We all came up with our own designs and discussed the pros and cons of each design.

Experimenting with Knex in class was extremely fun. This also shed some light on the differences between Knex and West Point Bridge Design. The most obvious difference is virtual vs. reality. While the West Point Bridge Design program more accurately depicts loads and specifies tension and compression, virtual programs are only estimates. They can help you make assumptions but one will not know how everything will react until it is designed with real materials on a small scale. I feel the program allows for more variety with design through materials because Knex only come in a standard thickness. The Knex allows for a tangible bridge design that can be tested in real life since computer programs contain errors and are not 100% accurate. Knex also allow for a person to use connections and “gussets’” on their bridge. This is something that is not taken into consideration in the program. I personally believe that the best way to test and create bridges is using something tangible and real, more specifically, a real small scale version after a version is tested through a computerized program.

-Carmen Mercado

Week 4: West Point Bridge Designer

       This past week in lab we discussed and reflected upon the most recent assignment, which involved the making of the “best” bridge in West Point Bridge Designer (WPBD). Here, we define “best” as being cheap yet serviceable. Each individual entered the data for their bridge in a survey that would be used during class to compare each other’s work. Ultimately, the cost of the best submitted bridge was slightly above $260,000. I found this to be a wonder, seeing as my bridge cost closer to $425,000. Therefore, the goal for the lab was to create another bridge using WPBD and once again see who could achieve the lowest cost. Within my team, we had a bit of trouble figuring how to do so until the last 20 minutes of class. I feel that if we had discovered our method earlier that we could have had a cheaper result. Since I had the cheapest design between the three of us, we decided we should alter the materials to obtain a lower cost. Needless to say, it worked: we examined and altered which bars could either be of a smaller diameter and/or hollow. By the end of the class, the cost was significantly lowered by more than $100,000. This coming week, we will begin using Knex to make our bridges. I hope to experiment more with the design during this process. 


        West Point Bridge Designer has been a helping hand during these first few weeks of introduction to truss bridges. However, I believe there are many pros and cons to the program in terms of accuracy. Pros of the program include the analyzation of the design in terms of cost and tension/compression forces. These are features that would otherwise have had to been researched and examined in great detail and time consumption. Consequently, cons of the program include limitation in design and over-exaggeration. WPBD is very limited in the sense that it does not allow you to view the structure from all angles and incorporate top/lower truss connection beams. Also, structures are greatly exaggerated during test mode; WPBD may generate a structure that is stably sound that may not be in actuality. In my opinion, these are huge flaws because they negate aspects that must be considered in physical existence. While WPBD has been a helpful tool in terms of understanding the notion of cost and tension/compression forces, I don’t believe it is an accurate vision of an executed design in reality. 


Chelsea Moss

Week 4 - WPBD

In my opinion the West Point Bridge Designer (WPBD) program has many faults. While it is a good reference and teaching tool especially for understanding truss’s and tension and compression, one should not use this to create a bride prototype. First off, this program exaggerated the downward displacement a bridge experiences when a load is applied, basically making every bridge look unstable. It also does not allow for one to create the top truss connection beams. This part is just as essential to the bridge. Two huge items that is also not taken into consideration is the gusset plates and weather forces. These also can make a big difference in the bridges stability.  Another thing I noticed was that it allowed for bridges to be made, that in reality are unsafe. There is not a single large bridge that I can think of that does not have some sort of upper safety barrier. Especially nowadays not a single company would allow for a bridge to be made without some sort of upper protection beam. WPBD allows for bridges with no top beam or support to be created and pass a load test when in reality it is just not safe. Overall, I think that the WPBD is a good learning tool, not a program for actual bridge testing and production.

Last week in lab we discussed bridge production on WPDB and how cost could be reduced. We were challenged to submit the cheapest bridge possible that was still considered “structurally” sound. At first thought this challenge didn’t seem difficult but considering the fact that my teammates and I all made somewhat expensive bridges this task was more difficult than anticipated. I tried making several new bridges from scratch but this failed quickly. Ultimately the best choice became altering Chelsea’s bridge and slightly changing the structure and material according to the values yielded by the load test. I was able to reduce the cost by more than $100,000 and if given more time I could have reduced it even further by re-creating the same structure with shorter beams.