Week4

Week 4

            The group accomplished a lot during last week’s lab.  During the first part of the lab each member worked in modifying their designs to optimize the strength to cost ratio.   After modifying each design the group came together to analyze and make a final pick on a bridge design.   The design that was picked had a cost of 260 thousand dollars initially but one of the group members realized that the price cost could be decreased even more.  No changes were made regarding the structure of the bridge; instead changing the building materials reduced the cost of the bridge.  Initially the bridge only used solid bars with the standard 140x140 thickness.  After a lot of modification the cost of the bridge was brought down to $241, 389.46.   

            West Point bridge design is a really good simulation for building a Knex bridge.  Although WPBD is a realistic representation o a real bridge, I wouldn’t recommend it to be used for building a real bridge.  The main problem with this program is that only considers the force of gravity and weight load.  A really important force that WPBD is not considering is the force of wind.  Wind is really important force that should be considered when designing and building a bridge.  If this force is not considered when designing a bridge, it would be very likely that the bridge would eventually collapse.  Also this program doesn’t consider other facts such resistance to natural disasters such as earthquakes and weather conditions.  Although I don’t recommend this program for building a real bridge, I think that it suits perfectly for this lab.    

Post Week 4

Last week during our lab period our group was required to bring our already done bridge designs to class so that as a group we could create our the best design possible and submit it to the competition. all of our designs were different. To create the best bridge possible we analyzed each individual member and how forces were acting on it. Based on that we continued by taking out any member that wasn't essential for the structure and minimizing the material used we cut costs at the maximum. Our final bridge design was estimated to cost around 250 thousand dollars, this came down from about an initial cost of 400 thousand.
West point bridge design is a very realistic representation of a real bridge. One of the problems that this program has is that apart from gravity it doesn't consider any other external forces. For example when a bridge is constructed the wind that interacts with the bridge is very important for the design. Something like what happened with the Tacoma Narrows bridge where the wind frequency was just right to make the bridge act the way it did. In this sense the program is unrealistic because it ignores other forces like age, wind, traffic accidents and more traffic. Other than that the program seems to accurately represent the forces a bridge has and although when the simulation runs the bridge bends exceedingly it still works well.

Week 4

During last week's lab the group worked own modifying our own bridge designs to achieve the lower possible cost. After editing all our designs we found the bridge that had the lowest cost near the end of class and worked together to finely edit the design to the best of our abilities.
Next week our group is going to review what must be done for assignment 2. Also we will start the process of how we can successfully build our chosen design out of Knex. We will have to adapt to use the pieces that are available to build a design that most closely resembles our WPBD design.
Major accomplishments achieved this week in lab were that our group was able to come up with two designs under $260,000.00 and eventually fine tune one below $250,000.00.
The biggest problems that I see arising next week in lab will be the group's ability to convert a design created on WPBD to an actual bridge constructed of Knex. The Knex will not grant us as much freedom in the positioning of bars and connecter plates as WPBD. Our design my need to be edited to fit the constraints of the Knex.
Many aspects are not addressed in the WPBD program that would come heavily into play in reality. Forces such as wind, rain, and erosion are important factors that could deteriorate the condition of a bridge to the point of failure. WPBD also only considers what will occur if one truck crosses the structure at a time, if a bridge is near failure with one truck on it for a short amount of time multiple vehicles on it for an extended period of time will be sure to result in failure. If the bridge is put in a heavily used area where traffic builds up it, it'll be sure to collapse under the large load. The design also doesn't consider the affects that the build up of snow and ice may cause either. The weather is the largest factor that will greatly affect how a bridge is built and depending on the location of the bridge certain factors must be considered.

Robert Weldon - Group 10

A1-Almendariz

A1-Almendariz

            In the second class we were assigned that each member of the group should design their own bridge.  The main objective of the assignment was to design a “safe” bridge that would have the best strength to cost ratio.  The bridge had some standard constraints and rules that they must obey: All bridges should be running through a “24” meter canyon.   Bridges should have a clear span meaning that they should not have any intermediate support.  Also they should not use any cable anchorages and use standard abutments.  They should be set to have a medium strength concrete (0.23 meters thick) two-lane roadway.  Finally through evaluation they should be able to support a standard load truck of 225kN.

            My bridge went through a series a changes to be able to reach what I think is a successful design.  Each change was made basically after testing the bridge watching for weak points and improving them.  I decided to initialize my design by using through Truss-Warren template.  I decided to use this template because I saw it as the strongest of all templates because I think that triangles are really successful in distributing the weight.  I decided to run the test by just using the template too see what were the main weak points that needed to be improved.  For this template the main weak points that I found was in the whole upper surface of the bridge.  The bridge would collapse completely, and the truck would not be able to even get on the bridge.  It is for this reason that I decided to add a similar second floor using the same idea of triangles as the original template.  After rerunning the test, there was a lot of improvement in the resistance of the bridge.  In difference from the first time, now truck would be able to run until the half of the bridge.  There was only three week points found that needed improvement.  There were two in each side of the second floor and one in the middle.  To be able to solve these weaknesses I decided to divide each section into two.  This would first shorten the size of each member and form two triangles.  With the changes made, the bridge was once more tested and its results were good.  The design did now have any single weak point, it was able to support the whole weight of the truck all the way through, and it didn’t bend significantly.  The final cost of the bridge design was $426, 912.12.  I think that with more time, the bridge design could be worked and improved to reduce its cost while keeping its strength.  From this design I was able to learn that triangle structures are really efficient in bridges and long members will have a lower strength.  The first image is from the final design in 2D from the "Drawing board view".  The second image when the bridge was been tested and the truck was right in the middle of it.  The last three images are from the "load test results".  

A1 Hidalgo

The goal for creating my design was to make the most cost efficient bridge but at the same time it has a good structure serves its purpose. The shape of bridge was made by first constructing a Prat truss on top of the bridge and when that failed a Warren type bridge was added under for support.

As I worked on the design of the bridge trial and error helped me to choose the best solutions for each of the problems that I was facing. for example the v shape that is in the middle of the top truss was made by trial and error. The bottom truss has a special shape it bulges in the middle section. By doing this the weight is better distributed throughout the bridge. For the top part of the bridge the cross bars used to go in the opposite direction (from the upper right corner to the left bottom corner). When I went and observed the Strawberry Mansion Bridge, I realized that if I switched the direction of the cross bars the bridge would be better supported and this proved to be true. The estimated cost of this bridge was 430 thousand dollars. When the cross bars were reoriented the cost went down by about 20 thousand dollars.
This design helped me learn that the height and length of the trusses have an effect of the the maximum stress that they can handle.

Week 2

During the second week of lab our group spent time exploring how to use the Westpoint Bridge Design. We explored the different ways of building a bridge and made conclusions of what were the most cost efective way of constructing a bridge. Among these trials the different ways of constructing a truss were implemented in sample designs to determine which was the most cost efficient. Our plan for the following lab session is to create a bridge design by combining the best aspects of each of our individual designs.
The following bridge is called the Strawberry Mansion Bridge, its located about 5 miles north along the Schuylkill. This bridge is an arch truss bridge and spans about 60 meters. While I was on my bike admiring the bridge, I saw how the cross bars of each section change their direction at the tops and bottoms of the bridges. Even if the arched structures weren't there the trusses would still be structurally sound. Since the direction of the slope of the cross bars are opposite to how the actual bridge is affected by the force of gravity.

Week 2

In last week's lab my group learned how to create the blog. We also learned how the competition was to be set up and what was expected of us.
In the upcoming we our team will compare the bridges we all submitted. We will see whose bridge was able to hold the load with the least amount of tension in each bar while always keeping the price in mind.
Major accomplishments for this week include understanding the concept of truss bridges. With the basic knowledge of truss bridges we were able able to use WPBD to construct a rough design and begin editing it to find out which designs work best.
Issues that need to be faced is making a design that can both be put together easily, but with strength and cost in mind.
The three questions I have are: is there any guidebooks that compare different types of truss designs on Drexel library's site? Is there a source of current truss bridges in use in America? Is there a source for all truss bridge failures?

Robert Weldon - Group 10

A1 - Weldon

The goal of this bridge design is that it will be able to span the canyon for the cheapest cost possible using a truss design. I made my bridge in the shape I did because it is able to incorporate the most number of triangles possible in a compact design. The design uses intersecting triangles to help give the bridge the most possible strength.

During my design process the initial design of the bridge involved only large triangles with no small triangles present. I had to added bars to certain area to hold the bridge together and insure failure didn't occur. I tried building the bridge at different heights, from the road to the top part of the bridge, and didn't find a large difference.
The current cost of my bridge is at $408,247.96. I believe with further time I would be able to discovery better arrangements of triangles that would require the use of less material. If I had more knowledge of trusses and what arrangements work best for certain designs, I would easily be able to build a strong and cheap bridge design.
What I learned from designing the bridge is that extremely large and extremely small triangles don't work best, but instead a size in the middle. Also putting as many triangles as you can in a build isn't efficient either because the bridge may be strong, but the price will be enormous. I figure that intersecting triangles are the best strength to cost ratio.

Week 1    

          In the first week class we were introduced to the bridge building project.  Instructors introduced the basic rules that would play a significant role through the project as well as how it would carry out.  The most important fact that was thought was that we had to construct a bridge, which would have a good cost to strength ratio.  This means that it should be able to support the maximum weight possible while keeping it as cheap as possible.  Also we were slightly introduced on how the bridges will be tested in the competition.  After the instructor finished introducing the project had a chance to set up our website, sign into west point bridge design website, and get to know our team and exchange our contact information.  In the next week that our group will meet, we would keen on working on the next assignment and part of the project. 

            To be able to have a successful teamwork in a group project a group has to take several things under consideration.  The most important of all I think that is respect for each other ideas, equal cooperation from each member, and use each member’s skills successfully.  Cooperation is one of the biggest issues I had to deal before in previous group projects.  It is really hard to be able to accomplish a group project successfully if all team members don’t cooperate the same way.  If all of them are able to cooperate equally, the can all put their strengths together and come up with an excellent final product.  For this group I don’t think that we would be meeting this obstacle and if we do we must deal as soon as possible and with patience.  Also to be able to have a successful teamwork and the best final product possible we have to respect each other ideas and use each other’s skills successfully.    

During last week's lab time we were thoroughly introduced to the project that we are going to tackle this term. We basically have to construct a bridge that can support a maximum weight while keeping it as cheap as possible. During this time we also had the chance to set up our website, sign into the west point bridge design website and exchange contact information. I think that one of the most important aspects that our group has to have good communication and have respect for the other members of the group. During this week we will continue working together and figuring out our next assignment.

Throughout this project our group will be working collectively and we will be encountering various obstacles. One of these obstacles will be cooperation, in the past I have been faced with issues concerning cooperation so I think I'm ready for any problem. I will encounter them with tranquility and an open mind. any problem that we may encounter I will try to approach it by analyzing it and seeing it objectively rather than personally or emotionally. I think this will help our group be as effective and efficient as we can. 

-Juan Hidalgo, Group 10

This week during lab our group learned the main aspects of the bridge design competition and what is expected of us. The competition is to be conducted to see who can build the best truss design for a bridge that is only supported at two spots and able to hold the most weight until failure. This week we were successfully able to register for the West Point Bridge Design competition and were able to make this blog. Next week, our group will begin to work on starting our design for the WPBD competition. Issues we are going to face is creating a design that will be strong enough to hold a load while being light and compact at the same time. Some issues that may arise that relate to teamwork is properly disturbing work which can easily be addressed by identifying what has to be done and then equally separating the work. As each member is going to initially create there own bridge design, it will be hard to come to a compromise on which design is best to use. I believe we can fix this by using the information that was collected and use this to determine the best aspects that will help the overall design of our truss bridge.

Robert Weldon, Group 10