Week 10 - Greenwood

Looking back, I can say for sure that I have learned much that I did not know before from this module as a whole.  The bridge designing process, from the initial stage to the final, is overall much more in depth and complicated than I had ever imagined.  From the past ten weeks, I have learned about different kinds of bridges, how bridges work, why they are important, and most importantly how they are finally built.  I have also learned some of the basic math behind the magical force dispersing properties of the truss system of construction.  Overall, I am much more generally aware of the design process as an engineer from this module.

The least beneficial aspect of this course was probably the lack of variety in the weekly work we were required to complete.  Every week it was the same: lecture/build in lab, then blog post.  With a longer post due every other week or so.  While this was not a huge issue, the basic busy work just was not beneficial to my experience.

On the other hand, though, the most beneficial experience was the teamwork I witnessed and was a part of throughout the process.  My team completed everything required of us and still came in second place, making me very excited and proud.  I now understand why professor Mitchell put such an emphasis on teamwork in the beginning of the course.  It truly is one of the most important aspects of being an engineer; working with other engineers.

Overall I learned very much through the requirements of this course and would recommend either keeping it in engr 103 or adding it to engr 102 as an option.

A4- Greenwood, Carr, Banyas

Final Report - Assignment 4

John Greenwood, Kevin Carr, Jordan Banyas

 Bridges have been and will always be a stunning reminder of human ingenuity. The ability to cross large expanses or bodies of water without flying is one of the most useful creations mankind has ever imagined. Modern bridges have become much more advanced due to increasing needs in many areas. These areas include, but are not limited to, safety, aesthetics, and cost-effectiveness. Therefore, the goal of this engineering 103 module was to imagine, design, and ultimately create the most efficient and safe bridge among competitors. In order to accomplish this task, weeks of planning and teamwork were required to build a bridge using K-nex building pieces. The bridge would then be tested, spanning a 36 inch gap and holding a bucket which would hold an increasing amount of sand. The bridge team that calls itself “Three Pikes on a Bridge” created and met all of the specific building requirements, and eventually held 58.6 pounds. Closer inspection of the creation would reveal that it was a truss bridge. Trusses are the most common method of building strength between members in a bridge. Basically, a truss is a series of triangles formed by the beams, or members, in a structure. A triangle is the strongest possible shape to arrange these members in; therefore, trusses disperse the force between them almost perfectly when arranged correctly.

At the beginning of the term, “Three Pikes on a Bridge” had one goal and one goal only; to construct the most cost efficient bridge. Throughout the course of the class the determination did not waiver, as useful information was provided along the way. West Point Bridge Design (WPBD) was the first tool introduced during the bridge building process. This helped greatly, as it was a basic introduction to the bridge building experience. Through WPBD a multitude of lessons were learned. The first lesson was how to create a successful bridge. To accomplish such a task the weight of the bridge itself must be taken into consideration. In addition, the group learned that the simplest design can be the best design for it uses the least number of pieces. Finally, this program conveyed the message that a plethora of tests of many designs leads to a polished and effective one. After the WPBD assignment was completed, the group began to eagerly work with the K-nex in preparation for the first bridge design competition.

Figure 1- Original Bridge Design

During the first bridge design competition, the constraints were clearly presented. The Bridge had to span two feet and be a minimum of three inches wide. Attached above is a picture of our first bridge (figure 1). It was found to have tremendous vertical strength, but the sheer tension snapped the bridge once the weight exceeded seventeen pounds. Due to the way the bridge broke, the group felt as though the bridge needed stronger cross braces to hold it steady while weight was being applied. Throughout the course of the class from week to week the members tried different support structures. The group suffered many disappointments of initial high expectations. Once the truss analysis assignment was given, the group quickly realized the reoccurring problem. To add strength to the bridge, it needed to be taller. At this point, the vertical force would be dispersed over a greater area, thus being able to hold more weight. Thankfully this discovery was made just in time to help the group perform exceptionally in the competition.
Through trial and error, the group found the strongest design for the side of the bridge to be an X-shaped structure. This utilized the blue two-inch pieces held together by the 360-degree white gusset-plates. To handle the sheer tension factor, red five inch pieces were used in a zigzag like pattern and held together by two blue 360 degree gusset-plate pieces. These gusset-plates were also oriented to connect the bottom of the bridge with the next layer of the bridge. They held yellow three inch pieces together. The end of the bridge was the only part that was not free standing; therefore, most of the force would be imposed on the ends. Due to this, extreme precautions were taken during the construction of the ends. The group utilized the small one inch pieces combined with the yellow 180 degree connectors. Once this portion was built, the group decided it would be an excellent idea to add a second truss on top of the original. The second layer was much like the first except the 360 degree gusset-plates were oriented differently. Such a difference was the orientation of the red five inch piece trusses. Formerly in a zigzag fashion, the pieces were then connected diagonally in an alternating fashion. A picture of the final bridge has been attached below (figure 2). Overall, 369 pieces were used during the construction of the final bridge which cost 520,000 dollars and held 58.6 pounds. This means the bridge had a cost to weight ratio of 8,873.72 dollars per pound.

Figure 2 - Final Bridge Design

Upon testing the completed bridge, which met every requirement and standard of the module, the bridge exceeded initial predictions of a 45 pound failure load by a whopping 13.6 pounds. The load of 58.6 pounds was the breaking point of the truss. Sadly, the completed design came short of the group’s goal by about 300 dollars per pound. Three Pikes on a Bridge’s final creation placed as the second lowest cost per pound held among the class. When the point of failure was inspected more closely, it was discovered that the actual failure mode occurred in one of the lower members about 2/3 across the bridge. This may have been due to any number of problems, including loose gusset plates or an off-angle point of loading. Regardless of the point of failure, the group considered the bridge a great success.

After many tests and revisions to the design, this bridge performed in ways that were unexpected. One of the main performances that shocked the group was the amount of load that it held. It was collectively estimated that the bridge would hold close to 45 pounds. However, the truss actually exceeded this estimate quite significantly, holding 58.6 pounds. In addition to the load carried, one of the other things that contradicted with predictions was the failure point of the truss. The agreed position of failure was the end of the truss for it was constructed on an angle and the force was dispersed to one point. It was believed that the force of the load would separate the member from the piece that rested on the stand. The actual failure point was the middle of the truss. In summation, the truss split in half. It was concluded that the truss was very rigid and had a well-balanced dispersion of forces. In contrary to the group's false estimates there was one thing that was parallel to predictions. This happened to be the way of failure. It was established that the truss would not fail gracefully and it did not. It happened to be a quick and violent failure. This was due to the rigidity of the members and structure of the overall design. The group was extremely satisfied with the bridge's performance for it found a spot at second place for the section.

Although the performance of the truss proved to be very successful, there are potential revisions that could have been made. If given another chance, some design alteration would include increasing the height of the truss. By doubling the height of the truss, the load held more than doubled from previous tests. The most contributing factor to such improvement was the vertical dispersion of forces. Therefore, a potential addition would be a truss below the resting point. This increase of vertical span would prove to be quite affective for designs. Moreover, one mistake made was the orientation of the board on the bridge. It was perpendicular to the truss and had a lot of focus on the center. If given another chance the long side of the board would be oriented parallel to the long span of the truss. It would lead to a more even dispersion of forces and would yield a higher carrying capacity. To greater enforce this change the group would also change the gusset plates to make a flat surface for the plate to lie down. This would ensure a sturdy base and minimal chance for slipping or uneven placement.

Week 10 Blog Post

This term has taught me many things regarding bridge design.  One of the main things is that I learned the importance of triangles in a design.  I will never forget their importance.  Moreover, I value the fact that I now know truss analysis and multiple tests lead to a stronger and more efficient truss.  These were the most beneficial lessons on the course.  Trial and error is key.  One thing that I found to be the strongest aspect of this course was the application of WPBD.  This program allowed a significant number of tests in a short amount of time.  The computer generation proved to be very useful in the design process.  The weakest part of this course was the application of a blog.  It was least beneficial to me.  I believe that the engineering notebooks would have been just as effective.  Moreover, this would enable better designed bridges due to the grid lines.  One final thing I learned is that the height of a bridge greatly strengthens it.  The vertical dispersion of forces proved to be extremely helpful in creating a strong truss.

Week 10 blog Post Jordan Banyas

Overall this class was developed to further our understanding of truss analysis, support structures, and bridge building in general. That being said, I believe through this class I now have a much better understanding in all three categories. However, every class has it's ups and downs. The only main complaint I have about my experience in bridge building was that we spent too much time with West Point Bridge Design. Although that helped us understand how bridges worked and how to make the best support structure in that given technology, it did not help us with our over all project of building a bridge that much simply because the forces imposed upon the WPBD bridge was completely different then that of which we exerted on the K-NEX bridge. I think if you were to shorten that section of the class and use that time to teach about truss and joint analysis, the time would be better served. The most beneficial part of this class in my mind was the trial and error period. From week to week my group members and I would come up with a completely new bridge design and test it, record it's strengths and weaknesses, and figure out a way to make it better. Through this we were able to learn a multitude of different ways to improve our support structure. Our hard work came to fruition when our group built the most efficient bridge (or at least most efficient bridge that followed all of the constraints) during last weeks final testing period.

week 8 blog post Jordan Banyas

Through our bridge designing process, we learned that the way to add strength to your bridge is to add height to it. This helps disperse the vertical forces more effectively. This week we re-designed our bridge's truss system as well as adding a new top layer. Our final design includes 369 pieces and costs 520,000 dollars. we hope it will hold around 45-50 pounds.

What I learned

Throughout the term, each of our individual designs changed quite significantly.  The main reason for our changes was because of failure from testing.  I believe that the testing portion of the design process is the most important step for it gives us the most information.  Some of the information given are failure points, durability, a transfer of forces.  With this data, our group was able to formulate a very effective truss.  Some specific design hints were that the design should have a large height in order to evenly distribute the force across more member.  This was derives through many tests.  Testing yields very helpful knowledge.

Greenwood - Week 8

At this point we have discovered force in truss members using the Joint Method form of analysis.  It was an easy enough approach to the problem of force in long members on real bridges, and I believe it can be applied into real applications.  For example our Knex bridge can and should be analyzed mathematically before we attempt to apply any extraneous weight to it.  Actual engineers use math as a tool everyday to make sure their ideas can come to life, and we are no different.  Safety, usefulness, and financial awareness are all issues which can be addressed using simple math and physics.  If a bridge breaks due to a problem that could have been foreseen using a pencil and paper, there is no excuse for this laziness.
Down the line I believe I would like to analyze some of the factors which contribute to the swaying of the bridges we have seen in lab.  It obviously is an issue with the joints of the trusses, but there must be a way to look at these problems on paper before we apply them in lab.  It seems that Knex joints are not very strong, but that should not matter with a proper design.  This week and next week our group will be working hard to look at our bridge very closely to analyze any problem we may foresee.