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.

Jonathan - Week 8 Blog Entry

Previously in ENGR-103, our group began to prepare for Assignment 3. We were initially confused as to what we had to do, but we managed to ask DJ for help and he put us on the right road to tackle this assignment. We also discussed a bit more as to how we will modify our bridge to meet the 3' mark and how we are going to add a 3" x 2" tunnel inside. A major accomplishment is that we have an idea for what kind of bridge we are going to bring in next week. We are still deciding between two very different designs, one being very lightweight and the other being sturdy, but requires more pieces.  The issue we have is working on the rest of the third assignment because it looks relatively challenging. 

The method of analysis we are doing for Assignment 3 is good for getting the bare basics down for a bridge's design. This does not factor in other variables such as wind, earthquakes and large amount of cars. Therefore, if you wanted to know if the bridge will stand up, then these calculations are all you need, but a real bridge has to do much more than that. If I could analyze further, I would probably try to get more information about the geography around the bridge. That way, I could see if it is in a very windy location, or if earthquakes are frequent, I can change the supports to match accordingly. 

A3- Fischer

1) Calculations

2) Results on the Trusses: (Positive is tension, Negative is compression)
Truss AB has -7.07 lb.
Truss AC has 4.99 lb.
Truss BC has 7.07 lb.
Truss BD has -9.99 lb.
Truss CE has 4.99 lb.
Truss DC has 7.07 lb.
Truss DE has -7.07 lb.

3)

4) Using the Bridge Designer is a lot quicker than doing all of the calculations by hand. However, it does have its restrictions such as only being able to add on loads in multiples of 5. An advantage of using the Bridge Designer is that it can scale the values of the length of all of the trusses or loads on a bridge. It keeps everything in proportion so if you want to create a larger bridge, all you would have to do is multiply each value until you get your desired number.

6) Now that I know how to properly use the Bridge designer, I can easily do many test runs to see which kind of pattern can sustain the most amount of load, while staying under the given "pill-out force" values. All that it takes are several guess and checks and see which bridge can survive while still not coming apart. The "Tensile Pull-Out Force" also shows that having three trusses connected to a gusset plate allows more force to build up before breaking. This can help us by making sure we try to add more connections in places that are weak.

Disel - Week 7 Blog Entry

Last week we were able to test our bridge. The bridge was able to hold 30 pounds of sand and it cost $243K. Even that our bridge was not the best I think that we got a good ratio in weight/price. We are trying to find out our weakest point of the bridge so we can make it stronger.  The main problem I think we had was that our length was exactly 2 feet and probably it should have been a little bit more so it would be more stable while testing it. We have to make the bridge 3 feet long for the final test so we are working on that. Based on the design of the bridge which is symmetrical I think that our bridge is still going to have a good ratio even after we make it longer.

For the Knex pieces I would like to know the tension force of each one of them. WPBD software tells me the tension of each piece so I am able to see where the bridge needs improvement. If I would know the tension forces for the Knex pieces I would play around with them to make the bridge cheaper and stronger since we already know the price of each piece. I guess by testing all of the pieces with how much weight they can hold before breaking like we do with the bridge, we can find out their tension force.

Skip - Week 7 Blog Entry

The prior week, our group was able to finally test out our bridge. The bridge for our group was a bridge that Diesel in our group designed, which was a under truss bridge. The bridge was able to withstand 30lbs of sand, and it cost about 250 thousand dollars. My teammates and I agreed to design our next bridge for next class. There are more restrictions in the new bridge. It must now span 3 feet instead of 2, and must have a hollow middle section that represents the part where vehicles can pass through. With these new restrictions, our group agreed to design a new bridge. The major accomplishment of this week was understanding what was good and what was bad about our bridge design. Our bridge was good because it was strong and firm in the up and down direction. The bridge did not bend or break during the test in this vertical direction. Our bridge was not good because it bent and twisted in a c shape which caused it to eventually break. We do not have any problems so we just have to think of a new bridge design that will follow the new guidelines.

For the Knex designs, I would like the numbers of compression (force/strength) and tension (force/strength) on the individual pieces and gusset plates. This will enable me to find out where there is most force so I could tell where I would have to reinforce. These numbers are shown in the West Point Bridge Designer, and using these numbers I was able to build a strong bridge on the program. In other words, If I have these numbers for the Knex bridge, I think I will be able to build a strong bridge that equally distributes the forces of the weight. I am already provided the price so I can play around with the bridge by adding or taking out pieces and seeing where the best balance is.