Week 4 Blog Update

Last week's lab was spent designing a bridge together with my group. We were able to incorporate key elements in design we discovered on our own and collaborate to create a bridge that only cost $226,559.12. We used simple geometric shapes to design our bridge and slimmed down every connection to cost as little as we could make it. Our goal was to make the lowest cost bridge that could still support the truck so we made everything as slim as possible without breaking. We also tested out different materials and see how they would affect our bridge and costs, but ultimately settled on carbon steel because of the lower cost and impressive strength. We also replaced as many bars on the bridge with hollow tubes to lower the cost dramatically. As for the design of the bridge, we learned from our experiments and experiences that an arch supported by triangles was one of the strongest shapes because of its ability to evenly distribute weight among the entire bridge and conserve money spent on parts. Our next step is to incorporate the lessons we learned through West Point Bridge Designer into our K'nex bridges.

West Point Bridge Designer is a great program to test the strength of bridge. It lets you test out different combinations and look at the data of tension and stress at each point to allow you to really push a bridge to its limits. It follows the AASHTO design specifics so it has a realistic expectation for your bridge. There are a variety of options to manipulate the materials used and the specifications of each material's size and construction to allow a greater variety in bridge design. Some of the limits presented by this program include not being able to design in the third dimension, since you're only allowed to manipulate one side of the bridge and have the other side by the symmetrical to the side you first created. It also does not consider any external forces like wind pushing on the bridge or allow you to stress test for different situations (earthquakes or floods). You're also limited to having a single truck test the bridge so you cannot test the limits of sturdier bridges. The bridge also completely resets itself after each truck pass, thus not allowing you to see the effects of fatigue on the bridge. Our experiences in WPBD revolved around making the cheapest bridge, while in reality it would be a bridge that is both cost effective and long lasting. Safety is the number one concern when it comes to real bridges and the bridges we worked on so far are definitely unsafe for actual use. WPBD is a good program to start on bridge design though because of its accuracy in calculating costs and the stress caused by loads on the bridge. It seems like the perfect program to test a concept bridge out or learn more about bridge design through experimentation.

Realities of WPBD- Week 4

During last week's lab, the three bridge designs which had been created using the specifications of the A1 assignment were analyzed.  After agreeing upon what elements of each design were most advantageous, a new design was created with cost being the most important influence in the design process.  The final design had a cost of $226,559.12 which was the lowest cost the group was able to attain while still allowing the truck to make its way across.  Before last week's lab, none of the group members were aware of the ability to change the material or the thickness of the members of the bridge which was used extensively to reduce the cost in the final design.  It was found that if a hollow tube was used, the member needed to be slightly thicker than if it were a solid bar.  The group also realized that the cost of manufacturing uncommon length and width combinations was higher than making slightly thicker members.  Ultimately, last week was used to experiment with ways to produce the most cost effective bridge as possible.  In the coming weeks experimentation on this subject will continue as well as the initial stages of creating a prototype using K'nex pieces. 

The West Point Bridge Designer (WPBD) software incorporates many aspects of the bridge design process which are fairly realistic; however, like any other computer simulation, it is not without some aspect of fantasy or a stretch of reality.  In terms of what the program does well, it creates a true design situation.  Users are afforded many freedoms when it comes to the configuration of their own design.  Even with so many freedoms, the program still considers conditions that would be present in a real-world situation.  WPBD demonstrates the reality of design trade-offs.  In any design, when one aspect of the design is optimized, problems arise in other areas.  WPBD stays true to this fact by exhibiting how changing one member's size will affect the force exerted on a surrounding member.  Something that is immeasurably important in the world of a structural engineer is building codes.  WPBD uses codes and regulations used by the AASHTO Bridge Design Specifications which allows the program to be as true to life as possible. 

In reality, the structural integrity of a bridge is the single most important factor in any design followed closely by cost reduction.  WPBD will deem a design invalid if the design fails the load test.  If the designer chooses to cut costs and thus cuts into the structural integrity of the bridge, the design will fail. 

As stated above, the WPBD program is not a flawless program.  Practicing engineers are responsible for designing all aspects of the bridge and evaluating their environmental impacts.  These aspects include but are not limited to, abutments, piers, roadways, decks, the complete three-dimensional structural system, connections, as well as many secondary members.  In WPBD, designers are only asked to develop the main trusses in a two-dimensional design window and make very basic decisions pertaining to the roadway and supports.  The program also does not consider fatigue, which is the tendency of a material to fail due to repetitive loading such as vehicular traffic.  WPBD only considers two types of vehicular loading and the weight of the bridge itself, but it does not account for things such as wind, snow, collision forces, and natural occurrences.  Although WPBD does demonstrate the deflection of the proposed bridge design, what it does not do is use this deflection data as a design criterion.

The West Point Bridge Designer software uses AASHTO truck loading to carry out the load test, but because the program only moves the truck from left to right this causes problems.  The AASHTO trucks have heavier rear axles than they do front axles and because the program only moves them across the bridge in one direction, an ideal design in the software may be asymmetrical.  In the real world, these trucks would potentially be traveling in both directions across the bridge which would cause an "ideal" WPBD design to fail.

Week 4

     In the past week, our team examined the three different bridge designs we came up with and designed a new bridge that minimized the cost.  The technique we used was to make a bridge that had a low number of members and that is low in relation to the surface of the road.  Originally, we all had designs that were very tall, by making a design that was short, the price was cut down tremendously.  The lowest we have been able cut the cost down to is $226,559.12.  We experimented with using hollow tubes versus solid bars.  The hollow tubes have to be much thicker than the solid bars but they are significantly less expensive than the solid bars.  Another interesting thing we found was just because the size of the members is smaller doesn't directly relate to the cost decreasing.  Sometimes we would decrease the thickness of the members and the cost would go up because it is not a standard size.  This was a minimal problem because then we had to check if the price decreases or increases as the size changes for each member.  We also found that every bridge design seems to have a minimum cost, there is a point where you cannot do much more to decrease the cost of the bridge.  We had many designs that we could not get the cost low enough to use.   Our major accomplishment was coming up with a bridge design that is very cost efficient however we still continue to look for ways to minimize the cost.  In the coming week, our goals are to start converting our design to knex to build a physical model to test and possibly changing the design as we progress.

     Now that we have been using West Point Bridge Designer for several weeks, we are beginning to see how realistic this program is for designing a real bridge.  It is a very realistic program for the intentions of introducing the structural design process, it is very simplified program that emphasizes the design process, not the detailed technical aspects of design.  It gives us the freedom to design whatever shapes we desire.  The program limits the design in ways like limiting span length and support configurations and the choices of material and member size are limited.  It also allows us to evaluate alternative designs and materials.  We can test the alternatives to see what is the best option.  When experimenting with changing one area it usually affects another area.  In the real world, there are codes that must be followed to make sure engineering is practiced with consistency and safety throughout the country, WPBD takes some of these codes into account.  Safety is always the most important factor, the cost is important but if the bridge is not safe and functional then the cost is irrelevant.  Cost reductions cannot be made if the safety of the bridge is compromised.  The cost calculation is also realistic because WPBD takes into account the cost for fabrication and assembly.  A degree of standardization in the selection of structural elements can cause the price to be reduced because there are not many unique pieces that need to be made, everything is consistent.  West Point Bridge Designer takes a lot of necessary elements into consideration when designing and testing our bridge designs.  It is also unrealistic in some ways.  When engineers design actual bridges, they are required to develop very detailed designs and cost estimates for the piers, roadways, and decks.  WPBD only allows us to develop very simplified designs and calculates the cost estimate for us.  It has us design the main trusses and the design is two-dimensional as opposed to three-dimensional that actual engineers work with.  Engineers also consider the environmental impact of the bridge, they examine its impact on water and ice in the body of water it is crossing and take fatigue into consideration.  WPBD does not take many different types of loading into consideration.  The program does not look at different forms of wind, snow, collision by vehicles and ships, or earthquakes.  Deflections are also a limitation that engineers have to consider, WPBD calculated deflections but does not use them as design criteria.  WPBD only tests truck movement from left to right.  In the design of an actual bridge, the movement in both directions must be considered.  The cost estimation is not accurate in WPBD, the concepts are taken into account but they actual cost estimation is not accurate.  Overall, West Point Bridge Designer introduces us to the design process but it is nothing like designing a real bridge.  

Questions for Mr. Jay Bhatt

What is the most common design used in truss bridges? What initial shape do they use and what types of cross beams are the most popular?

Are there different types of arcs we could use in our bridge design and how does each one vary in ability?

What materials are best suited for bridge design? What are the pros and cons of the most popular materials?

A1-THOMAS

My design goals revolved around having the cheapest bridge I could create that was still able to support the weight. I prioritized cost above all on this bridge, safety second and aesthetics third. I mostly concentrated on shaving off the final price as much as I could, thus the bridge isn't very safe since most of the parts have been stressed to almost the breaking point in order to reduce cost. The bridge isn't too bad aesthetically, it's symmetrical and has a good design to it. To make this bridge, I used a bridge I had designed in class, an arc based bridge with many supports. I replaced most of the support bars with hollow tubes and lowered the thickness of the steel wherever I could in order to get my final design. I didn't really experiment with other materials so I suppose some improvements could be made if I tried other materials. My final bridge cost was $243,142.97, which I was very happy with. Throughout the design, the only major things that happened to my design was carbon steel tubes where placed wherever I thought I could safely replace bars with and the all of the bars were made as slim as I could make them. I learned about the importance of incorporating arcs into your design and how they help distribute weight a lot more effectively than a rectangular shape. Using triangles to hold up the arc made for the strongest shape I could find. After coming up with that initial vision it was a matter of making it viable cost wise. The first iteration of the bridge was somewhere around $400,000 and I managed to change it around enough to get it to the price I got in the end. My bridge is extremely risky but it's functional and fits the criteria.

Week 3

Questions for Mr. Jay Bhatt:

1. Are there resources that allow us to look at bridges that failed that also show what could have been changed to make it a successful design?

2. Are there blueprints available for alternative designs for popular bridges?

3. Are there plans available of popular bridges that we have access to? 

Week 3:

In the past week, each team member designed a bridge that is successful using West Point Bridge Designer.   I experimented with different designs to figure out what is successful and what is not.  Our task for the week was assignment A1.   There were specific design constraints that had to be taken into account such as having an elevation of zero, no intermediate support, no cable anchorages, and medium strength concrete must be used.  Our major accomplishment this week was designing bridges that are effective and safe.  At this point there are no major issues that we have encountered.  There are small issues that are encountered in designing the bridges using West Point Bridge Designer when certain sections of the design were too weak or the cost is too high.  These problems are minor that are part of the design process.  In the coming week, we will continue to work on our bridge designs and analyze different parts of the three designs to come up with a combined final design that is effective. 

A1-HOWARD

                     Bridge Design:

                     Bridge Test with Truck:

                      Load Test Results:

The design goals that I started out with when designing this bridge were for it to be safe to use, cost efficient, and  aesthetically pleasing.  All of these factors were important but the most important was safety, second was cost, and third was the appearance.  I experimented with many different designs to find which types and components work the best for carrying loads before deciding to incorporate different components into a final design.  I started out using the templates that West Point Bridge Designer provides and building off of them in order to make them functional and unique.  I then began experimenting with my own original designs to make a design that was functional and creative.  I experimented by adding joints and beams in different places on the bridge where I thought they would be effective.  Occasionally there were parts on the bridge that were not necessary to include.  I designed my bridge using symmetry and patterns, I used a series of triangles to construct the bridge.  My current bridge is estimated to cost $468,308.63.  I predict that the cost can be decreased significantly by experimenting with size and material used.  The cost could be lowered by decreasing the thickness of certain members and using material other than solid carbon steel bars.  I overcompensated for the size of the members in relation to the stress put on them.  I have learned that triangles are the strongest shape and reinforced this fact by testing other shapes that failed.  I experimented with one design that incorporated parallelograms into it however when I slightly changed the design to use triangles instead of parallelograms, the design was much stronger and used a significantly lower number of members.  This program has also taught me a lot about the design process and about changing the design slightly to be significantly stronger.    

Questions for Mr. Jay Bhatt

Mr. Jay Bhatt,

Are there any resources where we would be able to find blueprints or designs of actual bridges as a way of analyzing the strengths and weaknesses of those bridges?

Is there a particular place where we could find information pertaining to the failure of specific bridges?

Are there any resources which will allow us to compare the pros and cons of specific building materials?

A1-CAMERON

In designing a bridge to meet the specifications of A1, my goals were to create an aesthetically pleasing bridge that was safe and cost efficient.  The most important factor was the safety, followed by cost, leaving visual appearance as my lowest priority.  The final design I chose to use, which is pictured above, was the cheapest way to incorporate all of the aforementioned goals. The picture below depicts the bridge while a truck is crossing over it.

The load test results are as follows:

When I had first begun designing the bridge, there was a very similar structure, but less structural pieces.  The cost was of course much lower, but when it came time to test the bridge it failed.  I then went to the other extreme and created far too many members to the point that it was astronomically expensive.  This final design creates a happy medium in a way that uses the minimum amount of members for this design to allow the truck to cross the river. 

At this stage, my bridge's projected cost is $429.653.47.  I expect this number to either decrease or remain somewhat stable with time and further knowledge due to the fact that the simulation shows a large amount of sagging.  I could potentially lower the cost by making the top of the trusses lower, but this could in turn create more sag.  If I add more members with a lower maximum height, I could reduce the cost by lowering the height but consequently raise the cost by adding more members; thus, maintaining a stable cost. 

Through designing this bridge, I have learned the true power of a triangle.  While in the design phase, I had experimented with parallelograms and one of two scenarios would play out.  The first scenario would be that the program would tell me that the structure was unstable and could not be tested, and the second scenario would be that the design could be tested but would have some sort of disfiguration that would cause the bridge to fail.  In very few cases did the parallelogram actually prove to be a successful design. 

Professor Mitchell's review covered many topics from what we can expect to see as the project progresses to what we need to be successful on the project. Teamwork is one of the key factors in projects such as this since there are due dates to meet. Having good teamwork relies on communication between team members and this can be achieved with anything from a simple email to a meeting to discuss plans. Me being a commuter student and my group mates being residents might present small problems with meeting times but I am determined to work around that. I believe we'll be able to keep a good schedule going and have our project progress in an organized and timely manner. Group meetings are important because they allow better sharing of ideas. We need a collaboration of everyone's ideas in order to make a design that have input from all members. Discussing possible iterations of the bridge can allow us to take the best elements from each design and combine them to form one that incorporates all of those elements. I plan on emphasizing collaboration of ideas in our group so we'll all have to play a role in each part of the project. My previous experiences with Engineering projects has shown me that field testing is very important so I hope we finish ahead of schedule so we have extra time to test our design and implement any changes that make the design more ideal. It's also important to record every major iteration to keep track of our project and see our progress and demonstrate our problem solving steps. One of the most important things to do in this project is to have fun and build cool bridges. Actually enjoying and taking interest in a project will always give better results than being indifferent about it.

The information on teamwork provided by Professor Mitchell was very helpful.  I have worked on team projects before, but I never considered many of the tasks that go along with a successful project.  I think that it would be very beneficial to have an established meeting time each week outside of class so that all three members know when it is going to be and can plan around it.  It is important that all three of us are there in order to make decisions and be productive in moving towards a successful result.  The fact that Stevie is a commuter student must be taken into account when finding a time to meet.  I also think it is important to have an agenda, end time, and minutes for each meeting so that we can make sure we are productive each time we meet.  Having minutes and an agenda can help us to organize our ideas and have our progress and ideas documented.  I think it will help to keep our records together so it is easy to see our progress from beginning to end.  A few problems that I anticipate is time management and having assigned roles in the group.  It would be very easy to put off major decisions and be forced to make the decisions at the end.  We can prevent these issues by having organized meetings and agendas so that we can accomplish what needs to be done on time.  As far as assigned roles in the group, I imagine that we will rotate roles and share parts of different roles from time to time.

After reviewing the material on teamwork prepared by Professor Mitchell, it is clear that there is a lot that goes into a group project.  The effort must be evenly distributed among us as the group members in such a way that we can play off of each others' strengths and weaknesses.  I was especially intrigued by the proposition of establishing a specified meeting time.  This would allow us to work around all three of our busy schedules and to ensure that every member could be present at each meeting, which is even more pertinent due to the fact that Stevie is a commuter student. 

Another piece of advice I find interesting is to take meeting minutes.  I have been to large meetings for various student organizations and have received the "minutes" usually the day afterwards, but I never considered using that concept for a small group project meeting.  I think it makes perfect sense because from my past experience with group projects there is either someone who missed something that was said or forgot what was discussed at a meeting.  Having meeting minutes allows each member to have a written form of what was discussed to refer back to for future questions. 

At this point in the project, the issues I can foresee include delegating tasks and maintaining good time management.  I think all of what I have discussed above can be used to solve these issues.  If we schedule structured meetings and set personal deadlines for ourselves we can have all of our tasks accomplished ahead of schedule which will allow extra time for revision.  The structured meetings will allow for us to create some type of order which will help us to more easily divide the work.  I think it might be a good idea if in lab this week we could designate a weekly time that could work for meetings.