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.

Week 4 Assignment: WPBD

            During this past week we reviewed the submissions for the A1 assignment in which each individual had to submit their own bridge. We talked about what defined a good bridge, and learned that the best bridge was defined as the lowest cost while still being serviceable. The best bridge that was submitted was in the $200,000 range, while most of the other bridges fell in the $300,000-$400,000 range. The rest of the class we worked on our groups individual designs to get the costs down and pick the best design in the end. This is hopefully the design we will use to build our real bridge using Knex. During this coming week members of my group are continuing to work on our bridge design to get the cost down while keeping the design the same but maybe using cheaper materials where it is possible.

            The West Point Bridge Designer is something we have been using for weeks now and have become very comfortable understanding. Overall, we have learned that what we see (in terns of the give of the bridge) is greatly exaggerated. When the truck is driving over the bridge and it is unstable, it dips down, which in real life wouldn’t be as large. If this were to happen on a bridge in real life, we learned, the bridge would dip down at most 1 inch. The program does do a great job with measuring the tension and compression forces however, which would be the same in real life. It also helps because it tells the user which piece in the bridge is having the most trouble so they can figure out where the repairs are needed.

A1 - Chelsea Moss

  This past week in lab, my group mates and I reflected upon last week’s assignment on teamwork, recognizing and resolving our individual issues. We then segued into the main topic of the course, while turning our attention to that lab’s powerpoint. Our professor emphasized the idea of a system and how it requires a particular balance of identified components in order to properly function. However, what if there is an imbalance of materials? We were shown the consequences of this through videos of famous bridge collapses. The videos were very validating for me as an engineer, and how absolutely crucial it is to test for all purposes from the debasement of weather and/or fatigue. This is true to any structure, however, bridges in particular are built to create a physical connection between two points that would otherwise be forgotten due to the sheer magnitude of the obstacle against our size. Bridges are truly a great feat to humanity and it is no wonder that great masses of people use them everyday. Consequently, this means that there is a fair amount of risk in terms of construction, which exemplifies the professor’s previous point on the importance of a system. Immediately following the powerpoint, our group returned to our work station to get started on the actual project. Kelsey and I experimented with West Point Bridge Designer and the different styles of trusses. Melissa focused on the blog, giving it an aesthetic appeal while maintaining professionalism. So far, I’m very happy with our group effort.

  In this upcoming week’s lab, we will have a guest speaker to discuss library resources and how to use them to our pivotal advantage. Mr. Jay Bhatt will demonstrate the power of library resources by answering our prepared questions about bridges. My questions include:

1. What are the key differences and advantages of Howe and Pratt truss bridge styles?
2. Why would an engineer design a truss as opposed to another bridge style?
3. What are the weaknesses of a truss bridge design?

Bridge Design:   The object of my bridge design was to keep the cost as low as possible while maintaining a sturdy frame. Obviously, my result was disappointing with a final market value of $423,582.56. My design originated from using a Howe Through Truss and a Pratt Deck Truss. I felt by combining these there would be less stress on the joints and therefore an accurate distribution of weight. I used Carbon Steel throughout but experimented with hollow tubes to lower the cost.

Test results: Based off my results, I don't think I obtained a proper balance of compression and tension, however I think I executed my idea as well as I could have. There is much room for improvement.

Chelsea Moss

A1- McSorley

My goal for this design was to have an original Truss Bridge, with supports on both the bottom and the top. I originally had just the triangles, but the bridge was too week, so I added downward supports on the top of the bridge to support it.

My bridge was originally only a top Truss bridge, but I added the bottom for extra support. I used Carbon steel throughout for its strength (even though it was the most expensive). Also I added crossbars on the top Truss because the triangle formation wasn't strong enough on its own.

My bridge currently costs $470, 270.98. This cost could be improved, however, if we replaced the strong carbon steel on the ends of the bridge with maybe something a bit cheaper. We would of course make sure that we watch the compression and tension when testing a different material, and compare it to the carbon steel to make sure it is safe. From this bridge design I have learned that there are millions of ways to build one bridge. When creating a bridge you kind of just start with a basic idea and add off of that as you go. Improvements can always be made, and a stronger bridge can always be created. 

Week 3- Bridge Analysis

This week I visited a local Bridge and took pictures of it… here’s what I thought!

Burlington Bristol Bridge (BBB)

Location: 

             Crossing the Delaware River from Burlington New Jersey to Bristol Township, Pennsylvania

Bridge type: 

             Truss with a steel vertical lift

Traffic condition:

Traffic is very heavy during rush hour traffic (7-9am & 4-6pm). For a 2 lane bridge many trucks pass over it at once. It seems to have heavy usage and during rush hours traffic is constantly backed up.

Overall Condition:

                The bridge seems to be old and it was built in 1931, so repairs seem to be done regularly. The metal seems to be rusting. As you drive over the bridge it is very shaky.  It seems unstable. This bridge is a major pathway to Philadelphia and should be monitored regularly considering the constant usage. Another major area of concern is the center span of the bridge. This span can be lifted by the action of two large concrete slabs of slightly greater weight than the lifted, span moving in a slow downward motion. This will block traffic when they are fully down, this allows for boats to pass underneath.  This adds another area of concern. This bridge is very old and any failure while a boat was passing would be catastrophic.

Problems:

·         Rusting

·         Unstable

·         Overall weight sustained on a daily basis

·         Traffic

·         Size (aka only 2 lanes)

·         Age

                         

Last week in lab, we discussed our previous posts on teamwork; how effective teamwork can be obtained and how to avoid problems within a group. We also discussed truss bridges and their importance. We also watched videos of famous bride failures. This showed how important it is to design a good stable bridge. After the group discussion we split back up into groups and begun working on the project. Chelsea and Kelsey worked on building bridges on West Point Bridge Designer. They experimented with different truss styles and found a few designs that worked. I, on the other hand worked on our Blog. I wanted it to look friendlier and appealing. I started adding posts about who my teammates are and formatted the entire page with anew background and theme colors. I’m glad I finally figured out how to use the site with the help of Oliver Tillman’s Blogging expertise. This week in class we will discuss the West Point Bridge Designs and choose one to make on a small scale. Can’t wait! J

-Melissa Mercado

A1 Mercado

1. The object of my bridge design is to create a bridge that worked and was sturdy as possible. My original design did not have the top section but it also sagged more. The top section was added for weight displacement.

2.                            

3.                              

4. Load test Results

 

5. I planned on keeping the design as simple as possible. Usually the simpler the design the better. This changed with the addition of the top piece for stability.

6.The final cost of my bridge was cost $592,297.07. The costs increased when I added the top portion for stability and changed the inner members to high strength low alloy steel. If I change the materials the cost will decrease immensely.

7. What I learned that building a bridge is easy but keeping the cost down is difficult.