Disel - Week 9 Blog Entry

Last week we were able to come up with two different designs for our bridge, but from the testing we all agreed that we should use the bridge Skip designed. It's performance was really good and we worked on some changes to make it cheaper so I think we are ready for the competition. The one I designed seemed good but when tested it would not hold more than 7 pounds. Even that I made some changes still is not as good as the other bridge Skip designed. I think we are going to be one of the teams with a good ratio weight/cost.

I learned a lot from this course. I learned a lot about truss bridges. I learned how and where is necessary to use triangles and where is not. I learned that the center of the bridge should always be the strongest part of the bridge. I also learned a simple way how forces are distributed. I learned how to use WPBD software which helps a lot in calculating the cost of a bridge and distribute the forces. The best thing about this course I think was the fact that we had to make a strong bridge but not forgetting the cost. From that I learned a lot about how construction industry works in real life. The competition with other teams made it really competitive.
I'm really happy with what I learned into this course and I think some of the things I learned here are going to help me majoring as a civil engineer.

Skip Week 9 Blog Entry

The prior week, we designed our final bridge for the next week when we will actually test out the bridge. Instead of building a bridge that could hold a huge amount of weight and cost a lot of money, I decided to build a bridge that could only hold a little bit of weight, but is cheap so that the cost to performance ratio is high.  I ended up building a bridge with a basic over truss design with many right triangles. I also used the long seven inch Knex pieces and used less gussets because the weak points were at the gussets on the previous bridges we looked at. I also designed it so  The cost is about $100,000 and when we tested it, it held 14.4 pounds. This is pretty good cost performance. Disel in my group designed a bridge that had more webs and smaller trusses, but when we tested it, it only held 7 pounds and it cost a lot more than my bridge design so we decided to go with my design. Disel's bridge broke more easily probably because he had many gussets and connectors which made it easier to break. He also had the sliding gusset plates which is a common place where the bridge ruptures. The coming week, we will test out my bridge design for the final test. We will try to make the bride cheaper and stronger in preparation for the final test to improve the cost performance. The major accomplishment this week was that we were able to design a bridge that will look very close to the final design. The bridge we have right now follows all the restrictions and we are happy with how it performed when we tested it. The only thing to do now is to improve on it. The problem is that I am not sure how to improve on it. I have made the bridge as cheap as possible for the current design, and I do not know if there are parts that I can remove. Otherwise, there are no problems within the team. We all agree with the current bridge design and we are helping each other out giving ideas for the bridge.

I learned that you must consider many things when you are designing a bridge. There are many steps when designing a bridge. One of the most important things that one must consider when designing a bridge is what the client wants the bridge to be. Does he want the sturdiest, strongest bridge possible or a very cheap bridge that is not as strong? Does it have to look interesting and unique with a suave design, because it will be a symbol of a city? In this course, we were required to build a bridge with the best cost performance. We had to balance out how much it can hold, with how much it costs. Another thing that is very important is considering the restrictions. A real bridge will definitely need to span a certain distance, be able to hold at least a certain amount, be durable so it will last for a long time, and there could also be a cost range. There are many restrictions that must be followed. In this course, for example, the final bridge for next week must span 36 inches and must have a hollow inside section 3 inches wide and 2 inches tall. After you have all these things, you can start designing your bridge. When designing bridges, you must also think about how the forces of tension and compression are distributed throughout the bridge. In the course, we used basic laws of physics to see how forces of weight were distributed throughout the members of the bridge. One thing you have to remember when dong these calculations is that this is disregarding many factors such as wind and the weight of the bridge itself. For this reason, we can only use these as a reference. One more thing I learned in designing bridges is that triangles are very strong stable shapes so are good to use in the designs. This is because in a two dimensional plane you cannot change the shape of triangles once you have one unlike rectangles where you can slide a side and make a different shape.

Jonathan Week 9 Blog Entry

Last week, we were able to make some more finishing touches to our bridges. Disel got to test his version of his bridge, but it didn't turn out as good as he expected. Soichiro got to test his bridge later in the class and it turned to be a lot cheaper that holds more weight. I think it cost around $100k and it held around 15 lbs. The key to making this bridge was that we didn't use any grooved pieces so we can try and make it pretty cheap. We will make more modifications to this bridge and we will probably end up using something similar to what we have now for the final bridge competition. I think the main fault in this bridge is that it follows the same pattern throughout the whole bridge and it is not reinforced in the middle so it might end up breaking down the center. Another problem is that we are unsure of how to improve the design of the bridge, since it held so much weight the first time.

I have learned a great deal about designing bridge from this class. One is that it is a lot easier to try a design out on the computer before you actually build it. This allows you to see basic outcomes as to where some of the pressure is building up on, so you can easily alter the bridge to dissipate the pressure. Another thing I have learned is that there isn't simply one good design that will win the competition. Since the competition relies on the weight/cost ratio, there are many ways to try and win. An example is that you can go for a very heavy bridge that holds a lot of weight, or the opposite, which seems to be more effective. Hand-calculating the pressures on the bridge is possible and is very important if there isn't a computer program that can do it for you as it can take quite a lot of time.

Skip Week 8 Blog Entry

The prior week, we started the analysis of the truss bridges. We used laws of physics and conservation of energy to calculate how the force of a load on a bridge is dispersed throughout a truss bridge. By doing so, we were able to calculate the tension and compression on the individual members of a truss bridge. We also made small modifications to the bridge and plan to further improve it. The coming week, my teammates and I agreed to make final modifications to the bridge to get it ready for the final weight load test. The major accomplishment this week was that we we able to learn how to analyze a truss bridge and how forces act on the bridge. Using this knowledge, we can improve our bridge and make it stronger. The major problem is that the bridge seems to be a little weak. My teammates and I have to work on the bridge to make it stronger.

This method of analysis is somewhat sufficient for a real bridge. It is somewhat sufficient because it uses actual laws of physics and you can see how the force of a weight on one point disperses throughout the bridge and you can see the tension and compression forces on the individual members of the bridge. The problem is that this only thinks about forces on one point. A bridge will have weight throughout the entire span and not just one point. The loads the bridges hold are not hanging straight from the gusset plates. It also disregards other factors such as wind which is very likely in real life. Another reason is that this disregards the weight of the bridge itself which will surely change the values. For these reasons, the analysis is sufficient to some extent.

For further analysis, I would like knowledge about the bending of the members. The analysis talks about tension and compression, but I do not know when the members would break. You could have a perfect bridge that holds a great amount of load, because it is strong against tension and compression but  I think that bending and breaking is another story. I would also like to learn about twisting. This is another factor that will affect the bridge. If I have all this information, I think I could do a legit analysis of the bridge.

Disel - Week 8 Blog Entry

We started working on our A3 assignment in our lab but the time was not sufficient to finish it. DJ  gave us really helpful instructions on how to calculate the tension forces for each point. We are also working on our final bridge design. The one we had before was a really good design but we have to change it because of the new restriction of 3" x 2" tunnel inside. Anyway we are doing good and I believe that in the end we are going to have a really good ratio weight/price.

The method of analysis is the first step in designing a real bridge but is not enough.This method just tells us how much weight the bridge is going to hold but it doesn't take in consideration earthquakes or wind effects. I think that to design a real bridge a lot more steps are needed but the one we are working on it should be the most important one.

A3 - Minami

In order to make the results of the hand analysis correspond to the online bridge designer, I had to scale the bridge side equally. In the hand analysis, the height of the bridge was 8", the span of the bridge was 24", and the weight at the middle point at the bottom was 15 pounds. In the bridge designer, I made it so that each grid spacing was 2" so the height is 4 spaces high, and spans a length of 12 spaces, and the weight remains the same so it is still 15. The bridge I made on the online bridge designer and the bridge of the hand analysis have a ratio of 1 to 2 respectively.


Knex Truss

I might use this type of analysis to improve the design of my bridge by looking at which parts of the bridge has the most tension and compression. Given the values for the pull-out force of the Knex, I can look at the online design and look at where the forces are greater than these values and see where I need to improve. I can also play around with the load and see how much weight can be held with the current design. This analysis will allow me to look at the individual parts of the bridge and which will allow me to modify the bridge part by part, and overall improve the bridge with best efficiency.

A3 - Spahija

 1) Calculations

 2) Results on the Trusses:
        Truss AB has -131.87 N
        Truss AC has 88.24 N
        Truss BC has 131.87 N
        Truss BD has -176.48 N
        Truss CE has 88.24 N
        Truss DC has 131.87 N
        Truss DE has -31.87 N

 3)

4) The results I calculated are relatively close to the results from Online Bridge Designer. My values differ from the program with 3% due to inability to define specific lengths and angles on the Online Bridge Designer. 

5) The best advantage that software has is that is a lot faster in calculating the value although they may not be 100% correct.

6) Now that I know hot to use the Bridge Designer I can test a lot of designs in a short amount of time and also find the place where the designs may be weak and try to fix them. The program shows me that most of the force is being placed in the middle of the bridge and there is where it need improvements. I think by dividing the big triangles into smaller ones might help distributing the force better.