Week 10

In last week’s lab we put our final three foot bridge design into COMP2. During the lab the week prior to COMP2 we were able to get our three foot bridge support 42.3 pounds. With this amount of weight the cost to weight ratio of the three foot to be around 9,000. Unfortunately during the competition our bridge was only able to support 31 pounds. The cost-weight ratio sky rocketed to 12,300. This made a huge difference. The bridge failed exactly where it did the previous week at the member where the over truss connected to the rest of the bridge. This bridge cost about $380,000 and I wish that our bridge went like out test did but overall our bridge did a lot better than our 2 foot bridge which is good because it was a good improvement.
         Over the course of this class there has been a ton of information that will help me out in my future endeavors. I learned a great deal about bridges, especially trusses. Also I learned about physical modeling them and weight distribution. The least beneficial portion of the class for me was the bridge design program that calculated compression and tension distribution. I did not find this program to be very helpful and I thought it made everything a bit more confusing than necessary. I think it would be better if WPBD did what that program did. I absolutely love doing anything hands on so being able to build my own bridge with k'nex it was great. I actually got lost a couple of times just coming up with different designs. To improve the class I would have there be more time for people to test their bridges before doing the competitions. Also, the constraints for the competitions should be made so there are no loop holes or ways to bend the rules at all. Finally, I would have each team to have to tries in the competitions in case of any mess ups that may make the results more accurate. Overall this course was a blast I had a ton of fun and took a lot from the course.

-Robert LaChance

Week 10 Blog Post

         Last week in lab, we tested our final three-foot bridge design. During week 8, our three foot bridge was able to successfully support 42.3 pounds. This result produced a cost-weight ratio of approximately 9,000. Unfortunately, last week it was only able to support 31 pounds. This resulted in a cost-weight ratio of 12,300. It is clear that the ten pounds made a great difference. The bridge failed right under the raised truss, similar to the previous week. This final bridge cost approximately $380,000. The cost to weight ratio is acceptable but I would prefer it was able to hold more. Overall, I'm happy with our final result.

         I learned a lot over the course of this class. I learned a great deal about bridges, especially trusses, physical modeling and weight distribution. The least beneficial portion of the class for me was the bridge design program that calculated compression and tension distribution. I found this program to be very confusing and frustrating. I would much rather prefer to calculate these properties by hand using trigonometry. The physical modeling segments of the lab and working with Knex were my favorite parts and the most beneficial for me. I always seem to learn more through hands-on working. To improve the class for future students, I would suggest opening a few more bridge testing stations. Once the time came where groups began to start testing, the stations became very crowded and getting the opportunity to test was often a struggle. Other than that however, the course was very well organized and I learned a lot. 

Week 10

Last week in class we got to test or final bridge design.  The testing went in order of predicted lowest cost to weight load ratio.  The strongest bridge in the class could hold about 102 pounds and cost around $800,000, but was still able to have the best cost to weight ratio.  Our group was disappointed in the way our bridge performed.  The bridge held about 31 pounds and cost around $380,000.  We were disappointed because in the previous the bridge held around 41 pounds and we had not modified anything.  After the testing was done everyone submitted how much his or her bridge had held.  It’s too bad this was the last time we got to play around with the bridge because I really enjoyed this lab.

            I couldn’t be any happier with the way this lab worked out.  I definitely like this design lab better than the previous two.  I feel like all of the topics were covered well.  This lab really made me learn to document everything because in the blog you would have to write about what happened.  Teamwork was also something that was really emphasized.  I felt like our group worked very well with each other.  The thing that was least beneficial was the truss analysis.  While it did teach how the to calculate forces on members there was no way to really apply it to your own bridge.  I think the quality of the fellows was the most beneficial.  They were much more helpful than the fellows from the last two terms.  They actually wanted to be there and wanted to help in any way possible.  I don’t really have any suggestions for next time.  This course was organized very well and a lot was learned.

Week 9 Post

In lab last week our group worked on our 3 foot bridge. Compared to our 2 foot bridge we had drastically changed the outlook of the entire bridge so we could cut down on the bridges cost which was our main issue in the last competition. For this bridge we also had to have a 2" by 3" passageway so cars and trucks could have space to cross our bridge. When we first came across this challenge it seemed to pose a problem but after some tweaking and playing with certain ideas we came to our basic design. One of the main goals we wanted to do for this bridge was to remove any grooved gusset plate that we had and find a way to replace them without getting too far away from our original design. When we removed the grooved gusset plates it immediately made a huge impact on the total cost of our bridge and it gave us some extra money to make other adjustments to improve the strength of our bridge. When we tested our 3 foot bridge it was able to support 42.3 lbs. which we were a bit shocked at proud of at the same time. Seeing as both out 2 foot and 3 foot bridges cost about the same and our 3 foot bridge held more weight than our 2 foot bridge we knew we were on the right track and have a chance to have the most cost effective bridge design. We hope to do well in the competition and maybe get atop the board and get some extra credit.
This term is almost and when I think about what I have learned in this course. I did not know a ton about how bridges actually functioned and how, but after this course I have a better understanding of them. I learned a lot about why truss bridges are a very commonly used bridge structure and how they are able to disperse weight on their members to hold the tremendous amount of weight that gets put on the each and every day. Also, I learned that the bridges we see out in the world are not there because someone just decides to come up with a plan for a bridge that would be the best bridge ever, but you have to take time and design a bridge that has a good amount of strength to it and is cost effective to build. Especially for our competitions, the cost-to-weight ratio was how we determined the effectiveness of our bridges by comparing the bridge's overall cost to the maximum amount of weight it can support. Weight distribution is a very important skill that was also taught to us in class. We used set of calculations to determine how the force, either tension or compression, would be dispersed throughout that entire structure. This class was definitely a good class to have because the thing I have learned and the skill set that I now have for being in this class will help me in my future endeavors.

-Robert LaChance

Week 9 Blog Post

Last week in lab, we made some major changes to our three-foot bridge design. We made these changes primarily to cut down on the bridge's overall cost. Another reason we implemented such major changes is to compensate for the additional constraint of a 2''x3'' rectangular space through the bridge. This constraint was added to simulate the construction of an actual bridge, allowing an area for vehicles to travel over. The biggest difference between our original bridge and the new bridge is the removal of all grooved gusset plates. We removed these pieces to significantly cut down on cost, being that the grooved plates were twice the price of standard gusset plates. After testing our new, three-foot bridge, we found that it was able to support 42.3 lbs. This was an incredible improvement being that our three foot bridge was able to hold more weight than our two foot bridge at almost the same cost. Needless to say, we will use the newest design for the competition.
The term is almost complete. Looking back, I learned a great deal about bridges, bridge design and bridge testing. I learned the most about truss bridges. I now know why truss bridges are so commonly used. They are able to support the most amount of weight due to their design. I also learned that you cannot simply judge a bridge's effectiveness by how much weight it can support, but you must also take into account the cost of the bridge. The cost-to-weight ratio is possibly the most efficient way to measure a bridge's effectiveness by comparing the bridge's overall cost to the maximum amount of weight it can support. Another important thing I learned was how to calculate weight distribution. Weight distribution is a very important set of calculations to perform when designing a bridge. These calculations will be able to determine how and where a bridge distributes weight in the form of tension and compression. The things I learned in this class will stay with me throughout my career as an engineer and I'm very thankful I had the opportunity to work with bridges.

Week 9

During last week in lab we got to work on our three-foot bridge design some more.  This was the last week we had to work on our design before the competition.  We built our bridge from scratch again.  Some things we kept in mind while making the bridge was to have a 2”X”3 hole through the middle.  Our first design looked like a square prism with trusses that looked like X’s on the side.  One thing that we did change from last time was the trusses on the inside of the bridge, which would prevent it from twisting.  When we tested the bridge it failed at around 24 pounds.  When we went back to the table we added some minor pieces that we thought would give the bridge more strength.  This ended up doing nothing.  In our final design we put a top truss on the square prism.  This design yielded about 40 pounds.  This was a success in our eyes so this is the design we will submit for the competition. 

            I came into this class with zero knowledge of bridges and came out knowing a ton more.  One thing that I noticed is different about me is that whenever I come across a bridge now I analyze and look at how it is built.  Trusses are one of the most important aspects of bridge design.  We learned how they distribute weight and make bridges that much stronger.  They have been around for about 100 years.  While designing the bridge you really learn how everything affects everything.  The best bridges are not just the ones that can hold the most weight or cost the least, but the ones that have the best cost to weight ratio.  One of the best technical things I learned how to do was figuring out compression and tension by doing physics/calculus.  When building a bridge there are many factors you have to account for including weather and aging.  The list of things that I learned can go on and on but these are just a few.

-John Watson

A3-Tillman

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4. By comparing the "Bridge Designer" sketch with the hand-written results, one will notice that the results do not match up. The reason for this is because the "Bridge Designer" program does not work in units. Scaling both results will use the same units for each method of calculation, resulting in equal final answers. 

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6. Using this type of analysis is a great way to visualize the weight distribution of our bridge. After seeing on our bridge where exactly weight and tension are highest, we may choose to strengthen these areas by using more Knex pieces or slightly rearranging the joints to decrease the chance of the bridge breaking at that point. Also, some pieces seem to not be managing any weight or tension at all. We will most likely remove these pieces to cut down on the bridge's overall cost.