Week 10: Duane

          In the previous week, the groups tested their bridges.  These bridges spanned about three feet.  Originally, the same design from the two foot bridge was used; just lengthened.  However, this did not produce the best results.  It was determined that in order to create a stronger bridge that spans three feet, the height of the bridge needed to be increased.  The bridge was modified completely.  The group tested this bridge on their own and determined that it too did not produce the best results.  It was contorting too much.  Once again, the bridge was taken apart and rebuilt, using part of the design from the very successful two foot bridge.  The bottom of both bridges have the same general design which evenly distributes the weight throughout the bridge.
          Teamwork was such a large part of this course.  Each person had a responsibility.  It was very important that each person had a say.  Each group member had a say in the bridge design and everyone contributed their ideas to make the bridge the strongest it could possibly be.  Documenting was very important.  Taking notes, taking pictures, and recording videos were very helpful when working on the weekly blog post.  Having the notes and pictures allowed for a better description of the progress made and also having pictures makes it easier for the reader to understand exactly what the design looks like.  Computer modeling such as West Point Bridge Designer provided very useful information about the group's design.  It provided forces and costs which allowed the group to modify the design to make it both stronger and more cost efficient.

A4: Breslin, Duane, and Ngov

BACKGROUND

The objective of this project was to design a bridge created from Knex pieces while considering the required constraints and parameters. The bridge needed to span a specific length while aiming to be most cost efficient. The efficiency was determined by dividing the total cost of the bridge by the total weight held. The first task in the bridge design process was to use computer software to get an understanding of to design a bridge. After information was gained, Knex pieces were used to create a bridge spanning two feet. Testing was done on the bridge to discover its strength. Following the testing, observation was done and calculations were taken. These results aided in the ability to lengthen the bridge to a span of three feet.

DESIGN PROCESS

Prior to the designing process, teams were established to set goals and collaborate during a ten week period to design the most cost efficient three foot bridge made from Knex pieces. Weekly progress was recorded on a team blog which showed a steady development of team work and design improvements. Many resources were utilized throughout the design process. The resources West Point Bridge Design, Knex pieces, Truss Analysis, and Bridge Designer were considered while creating the bridge throughout the entire ten week period.

The first asset used to aid the bridge design process, which spanned three feet, was a computer program called West Point Bridge Design. This program assisted students in understanding basic truss bridge designs, compression and tension forces, and the importance of cost. General truss designs of an arch, box, and under hang truss bridges were explored to allow groups to determine the most efficient design. A virtual simulation calculated the compression and tension forces of each member of the bridge. The greater the value of the force meant the member was weaker. This allowed for modifications to the design for improvement of the overall efficiency of the bridge design. In addition, different materials for members and gussets in West Point Bridge Design allowed students to consider the importance of cost. The strength of a material gave potential to increase the efficiency of the bridge while also raising the cost. Force and material were vital in the creation of a truss bridge throughout the Knex building process. This is because the ratio of the cost to weight determined the efficiency of the bridge. During the entire process, the cost of the design was extravagant. Consequently, the design was altered numerous times to decrease the cost while attempting to maintain the strength.

The next type of source that assisted in the development of the best bridge was Knex. Knex allowed a physical representation of how a bridge was built and failed. The construction with Knex pieces showed real life limitations. For example, the limited amount of members and gussets represented how manufactures do not have every size available for construction, while numerous fail factors can be physically seen. West Point Bridge Designer did not show geometric contortion like Knex. The bridge development through the use of Knex exposed vertical and horizontal failures while allowing failures to occur at multiple points on the bridge. This resulted in necessary changes to improve a similar example of a real bridge experiencing outside forces such as wind, earthquakes, and traffic. In addition, Knex allowed accessible and simple changes because every piece was readily available for modifications if necessary improvements were needed.

The following resource utilized was the concept of truss analysis. Calculations on the members of the bridge were calculated and the results were similar to the forces given from West Point Bridge Design. This reinforced the importance of improving the design at the weak members on the bridge to increase the efficiency. In addition, experiments with Knex pieces during the load testing allowed physical observations of the weakest members and contortion. The use of Bridge Designer also showed the weakest members of a basic bridge design. The disadvantage with the use Bridge Designer was the inability to input any design. The Bridge Designer program required triangular connections at every node. Nodes are similar to gussets in which they are the connections joints for members. The program did have an advantage where the general concept of any truss design could be applied and simply scaled. If the height was scaled by a factor of two, the forces of the members would decrease by roughly a factor of two.

In the final bridge created, every resource used was applied in designing the best possible bridge. The final bridge can be seen in Figure 1. The overall design was created after the observations of many bridge failures occurred during the load testing. Designs that did not include gussets with grooves appeared to withstand the most amount of weight. This resulted in using the least amount of grooved gussets; refer to Figure 2 for two groove gussets together forming a connection joint and Figure 3 to see a one groove gusset. The connection at the grooves would not fail as a result of weight but horizontal force. In addition, the cost was considered and determined that the use of the regular gussets had more of an advantage over the grooved gussets. Many sockets of the gussets held the maximum number of members possible to increase the pull out load and the load capacity. In addition, the height was increased to allow the forces to evenly distribute. The goal of the bridge was to create a design that would fail as a consequence of weight, not contortion or vertical and horizontal force. Throughout the improvements of creating the final design, the weakest members were constantly changed to decrease the force applied. After testing and considering prior resources, the predicted failure load was estimated to be at thirty-five pounds.

Figure 1: Final Design of Bridge. 

Figure 2: Two Groove Gussets Together.

Figure 3: One Groove Gusset.

FINAL DESIGN

            The numerous design attempts, research, analysis, and testings group one created a final design seen in Figure 1. The plan and elevation views can be seen in Figures 1 and Figure 4 respectively. After discussion and consideration of research, analysis, and testings, group one extended the height to eight and a half inches this is because it allowed more even distribution among all the members. In addition, the overall design from the previous bridge was kept because the strength and efficiency was effective. Also, the connection joints were altered because it was discovered that the gussets with grooves, as seen in Figure 2, was weaker then regular gussets without grooves. Another influential aspect was the design of the bottom of the structure. The cords on the bottom were pulled through the holes of the gussets to allow for more flexibility in the bridge; as a result, this allowed the bridge to withstand greater compression and tension forces. This cost and materials list can be seen below in an Excel spreadsheet in Figure 5. 

Figure 4: Plan View of Bridge.

Figure 5: Excel Spreadsheet of the Materials List.

The total number of Knex pieces used was 212 and cost $375, 500.

FINAL RESULTS
            The final bridge was tested by setting an apparatus on top of the bridge. This can be seen in Figure 6. Connected at the bottom of the loading apparatus was an empty bucket. The apparatus was placed as close to the center of the bridge to allow an even displacement of the weight throughout the members. The bucket was slowly filled with sand until the bridge failed. The weight the bridge supported until the failure was then placed on a scale to be found. In the final testing, the bridge spanned a length of three feet. This bridge was able to withstand a downward force of 32.2 pounds and failed as a result from weight. The weakest area of the design was at the reaction points of the structure.  Similar to the first design, the second bridge also had a graceful failure where the deflection of the bridge was visible. A bridge cannot be improved if it failed as a result of weight unless an entire design is created.

 Figure 6: Apparatus on a Bridge spanning three feet.

CONCLUSION
            The course showed how the process of designing a bridge can be applied to Knex pieces. After testing the bridge, group one was able to conclude that the bridge behaved as expected.  In terms of the final bridge, the failure was thought to be as a result of weight. The results confirmed this prediction as the sand was slowly poured into the bucket. The overall geometry of the bridge did not contort but failed as a result of the downward force of weight.  The failure point at a reaction point can be seen in Figure 7. The group knew after computer and computational analysis that the end points were the weakest parts of the bridge. The predicted downward force the bridge was expected to withstand 35 pounds.  After testing, it held 32.2 pounds giving the group roughly an eight percent error in their prediction. Different aspects of strategies in teamwork, calculations, computer testing, physical modeling, and physical testing were explored. The course allowed further development in each skill. 

Figure 7: Failure Point of Bridge After Load Testing.

FUTURE
            As a result of the testing, modifications could be made to improve the design of the bridges.  Members should be added to the side of the bridge in order to prevent the bridge from contorting.  In addition, more reinforcements towards the end of the reaction points would allow more even distributions in every member; consequently, the efficiency of the bridge would improve.  

Week 10: Amanda Ngov

Last week was the final testing of bridges. My group performed the load testing similarly to week 6. Sand was placed into a bucket that was suspended on an apparatus, while being hung at the middle of the bridge, until the bridge failed. No other alterations were made for the upcoming week because the course has ended. If goals were necessary for the next week, my group would have tried to improve the weakest point of the bridge at the reaction points to improve the efficiency of the design. This week was difficult because new designs were constantly being created to find the best bridge design out of Knex pieces. Discussions about our previous research was considered throughout the entire redesigning process. Different members suggested one design while other members preferred different designs and applications of the research done two weeks ago. In the end a similar design from the original was used after increasing the overall height of the bridge.

All topics that were intended for students to experience and learn from were presented in the course. Teamwork between my group, planning a sensible schedule, documenting the results of progress, and the process of designing and altering a bridge to improve the efficiency were taught. In addition, computer modeling in West Point Bridge Design, physical modeling with Knex pieces, forensic analysis of bridge failures, static analysis through calculations, and computer software were all utilized and vital in the bridge designing process of the course.

To be honest the entire class was beneficial because of the how hands-on experience. I do not believe that the class was a waste of time in any way. With this said, I believe that the class allowed students to focus on a real life situation on a scaled down version with different programs and kit. Also, I do not believe the class structure or curriculum needs to be altered.

On a side note, the website was extremely clean and easy to navigate. Use this for next year if the course will be available for students to take.

Week 10: Bridget Breslin

In the previous week, the team had redesigned the bridge completely for the thirty six inch span. The bridge was then tested during class. We had suspected that the bridge would hold somewhere in between thirty and thirty five pounds. After testing the bridge, it was able to hold 32.2 pounds. The efficiency cost was $11,599. I thought that the bridge would break in the middle due to the weight however it broke at the bottom side. Regardless the bridge held as much as had been predicted.

Looking back at the time spent in this course, I think that I really learned a lot. In every topic that was discussed there were elements that helped me to expand my thinking and understanding of how things work. At first, thinking about building a bridge out of Knex does not seem like a difficult task. However, it is a much bigger challenge. This course enabled me to think about how by adjusting part of the design, it could benefit or hurt another part. It also allowed me to understand real life situations a little bit better. Thinking about everything completed and used throughout the course, everything seemed to be beneficial. The software used helped students to get an understanding of how a bridge works but also to think of other factors that may not be as obvious when constructing a bridge. Even all of the people that were involved in the learning process were extremely helpful and excited about the project. This helped student to understand the task at hand better and become more excited to find out how everyone will do. I think the most beneficial thing for me was experimenting with the bridges. Being able to physically see what was wrong with the bridge gave me a better idea of how it should be adjusted and how the bridge actually works. Overall, this section was very educational and fun which made it easier to learn.

Week 9: Bridget Breslin

In week eight, the team’s main focus was to expand the bridge. The initial plan was to keep the original design of the 24 inch span and to adjust it to reach a span of 36 inches. After testing this design and modifying it many times, the team was able to conclude that this plan would not work. After much observation and discussion it was decided that the team would have to start from scratch with a new design. The new design for the bridge has an increased height. The bridge is much taller than was originally planned. However, even though the bridge was completely redesigned, many elements that appeared to be very successful in the old bridge were incorporated. The new bridge is more expensive, however is likely to hold around 35 pounds.

            Now that the term has come to an end and I have had more experience with bridge building, I have learned many things. One of the main things I learned is that building a bridge is not an easy task at all. There is a lot of thought that has to go into designing a bridge. Also, a design that may work in one instance many be a terrible idea in another. Each scenario is different from the next. However, looking back at styles and techniques of preexisting bridges can aid in the design of new bridges. Simple concepts seem to work extremely well, it is not necessary to get extremely fancy unless it is needed. Bridge design also forces you to think of how the entire product will be affected by one move rather than just one specific area. A bridge is an entire unit that relies on each member to work successfully.

Week 9: Team Update

In the previous week, the group worked on extending the bridge from a twenty four inch span to a thirty six inch span. This task turned out to be much harder than it was anticipated. The team initially decided to keep the original design of the twenty four inch span and to expand the bridge using the same pattern. After testing this idea, there was little success. The team then added and took away many different aspects of the design only to lead to failure. Each trial resulted in the bridge only being able to hold approximately twenty to twenty five pounds.

            After much review and consideration, it was determined that the bridge needed to be completely redesigned. Although the design for the twenty four inch span worked very well, modifying it to reach thirty six inches would not work properly. The new design is quite different but has many of the same elements. The bridge is a lot taller than the first design was and included many different types of structure beams on the inside of the bridge. However, some elements that remained the same were the thickness of the bridge, the use of triangles, the technique to allow bending and beams used on the sides of the bridge to minimize contortion. This design for the bridge costs about $373,500 and can hold potentially thirty five pounds.

Week 9: Duane

      In the previous week, the group extended the bridge that spanned a total of two feet to three feet.  The group kept the same design, and only modified the length.  The two foot design held 47.8 pounds, the same design, just a foot longer held only 28 pounds.  Not what the group was expecting to see.  However, I did notice that many other groups were observing the same results when testing their bridge.  So modifications were made.  The group tried to keep some details of the strong, original two foot bridge in the three foot design.  Some modifications include increasing both the height and width of the bridge.  While designing and testing the new bridge, major twisting was noticed and was at fault for the failure.  Once again, modifications were made to prevent the bridge from twisting.  While testing the newest design, there was very minor twisting noticed, and the bridge was failing because of weight and not twisting which was what the group was looking for.  One thing to keep in mind, while testing the bridge some of the pieces actually broke under the weight.  Pieces included the blue gusset plates.
      I have learned many things about bridge design.  Especially that it is a lot of "trial and error".  You are constantly testing designs and then making necessary modifications and then testing again.  There are many programs available to help in the design process as well.  A program such as West Point Bridge Design is very useful because it shows the tension and compression forces on each specific member of the bridge and can help to identify any weak parts of the bridge.  With calculations, the forces on a bridge can be computed.  This leads to the design of a much stronger bridge.  Finally, I also learned that when designing a bridge attention is not only focused on the strength, but also on the price.  This is very important to realize because the government or a company usually will have a budget for you to work within.

Week 9: Amanda Ngov

The previous week allowed my group to focus on improving the bridge more. We tested different types of designs with different members and realized that the design needed to be improved on dramatically. Although we were able to create a design that held 30 lbs on a three feet span, we wanted to create a more efficient bridge. Consequently, we decided to change the entire design for the upcoming week. Research on methods to improve any type of truss design during the week was taken to consideration while recreating a bridge. It was noted that more members attached to the gussets allowed a higher weight load for the bridge. The difficulty during the reconstruction of the bridge was finding a starting point. Some members of the group were unwilling to recreate a different design because the original design did extraordinarily well during the load test, but others were willing to create the most efficient bridge. After discussion, the group decided to create a new design and test it. The design that held less weight then the new design would not be used.

In this overall experience of designing and creating a bridge, I learned how tedious the process can be. One computer program or kit can be utilized; on the other hand, numerous resources, observations and research should be considered to design a bridge. New ideas are  constantly being discovered so research is needed to experience new materials or resource to create an efficient bridge. In addition, observations of other bridge failures and successes should be taken into consideration for designs. Also, there are pros and cons to any resource and tool to build a bridge. Computer programs can give numerical values and estimates of forces but hands on kit such as Knex can show how limited certain materials are to a purchaser. Lastly, research to find more design types or methods of improving a design is vital. Discovering a site where people have done studies on number of members used in a connection joint helped my group in creating the final design. The process has shown me to explore numerous methods of designing a bridge and approaching an idea.

Comp 2: Breslin, Corey, and Ngov

Group 1 from section 035 has come to a final decision for a truss bridge. After many deliberations, experiments, and observations it was decided that a new idea for a bridge was required to make the most efficient bridge. The bridge now has a few more connection joints and many more members to allow a more graceful failure. After research and observing other bridges' failures, it appears that the failure will occur on the ends of the bridge near the reaction point. It is believed to be towards the end because there is extremely little support compared to the other connection points on the bridge. The total number of pieces used are 212 and the total cost is $373,500. It is believed that the bridge will hold roughly 35 lbs.

Week 8: Duane

    In the previous week, the group completed two tasks.  One, analyzing the forces on the members of the bridge.  Two, lengthening the bridge.  The bridge was converted from a two foot long design to a three foot long design.  One problem noticed when testing the two foot bridge was that it was just two feet, giving the group a problem when trying to place the bridge on the supports.  This new design is approximately three feet seven inches in length.  Having the extra inches will be very helpful when positioning the bridge on the supports. Analyzing the forces of the bridge was no easy task.  However, it is extremely helpful when you know the forces.
    Knowing the forces on each member is very important and crucial to make the bridge the strongest it can possibly be.  This method of analysis will be very helpful in making the group's bridge stronger.  Knowing the forces on each member will allow the group to strengthen those members.  This method is also time-saving, the group can determine the strength of the bridge without physically testing it.

Week 8: Bridget Breslin

In the previous week, the group had worked on two different aspects of the bridge project. The most difficult part of the week was analyzing the forces that were acting on the bridge. Calculations were completed to understand the mechanics of the bridge and get a better idea of how it actually worked. These calculations allowed our group to see the different weak points and strong points in the bridge structure. Having the calculations completed will allow the group to know exactly how and where to adjust the bridge to make it as strong as it possibly can. The group also worked on converting the bridge from its original two foot design into a three foot span design. The new design for the bridge has to be able to extent over a length of three feet. We decided to stick the original design pattern, just adding more parts to extend the length. After this was completed the bridge now has a length that is about three feet seven inches. Making the bridge longer allows for more leeway to position the bridge as needed during testing, whereas in the last test the bridge had a length of just about two feet, making it difficult to configure against the supports. I think in the upcoming week the team will have the greatest problem figuring out how to apply information gained from the analysis to improve the bridge design.

I believe the method of analysis used is extremely helpful. It allows one to see the strengths and flaws of the bridge without having to physically test it. The method of joints seems as if it would be sufficient for a real bridge, however would be more complicated. This method could be used to see how strong the bridge is and by using prior knowledge of bridge failures and the materials of the bridge one can make predictions of how the bridge design would work. However, further knowledge of location of the bridge would help to make better predictions. Factors of nature could affect the function of the bridge. Wind, rain, earthquakes and other types of natural disasters can cause a change in the forces on the bridge; having these numbers will help to make a better analysis.

A3- Truss Analysis: Breslin

To determine the forcing acting on the member of a bridge, the Method of Joints was used. In this example the height is 6 inches, the length was 24 inches and the weight of the load is 10 pounds.

Below is a diagram of the diagram of the simple Truss Bridge with a table of the Member to Member forces.

After completing the analysis of the simple truss bridge by hand, a program called Bridge Designer was used. This program allowed the computer to determine the areas of tension and compression in the bridge.   The figure below is the result of the simple truss bridge in Bridge Designer. The red lines represent tension and the blue lines represent compression.

The results of the hand analysis match the results of the Bridge Designer analysis. When recreating the analysis in the Bridge Designer, it is important to make sure that the bridge is to scale. The bridge in the computer program must have the same dimensions in order to calculate the correct forces and produce the same results as the hand analysis. If the two do not match up then the bridge has not been scaled the proper way.

In the Bridge Designer program, there are specific constraints in the program which does not allow the proper analysis of the Knex Bridge. The program does not allow for the correct representation of the bridge structure. Without all of the members of the bridge being represented properly, the forces of the bridge in the program do not correspond with the forces in the actual bridge. Another important factor when calculating the forces on the Knex Bridge is to use proper scaling. Whether hand analyzing or computer analyzing, scaling is important to determine the correct forces.

The testing information about Knex joints can be extremely helpful when analyzing the bridge. By using the average strength of each joint in the bridge, one can use the Method of Joints analysis to determine how strong the bridge design is and then find ways to strengthen the regions of the bridge that are weakest. This type of analysis can help one to understand the mechanics of the bridge design and know how and where to improve the structure.

A3: Truss Analysis - Corey Duane

These are the calculations performed to determine the forces in the truss members of a bridge that has a height of 6", a span of 24", and a load of 10 pounds.

This table shows the member-to-member forces, a positive number means tension and a negative means compression.

This figure shows the screen capture of the bridge designer for the above analysis.

    To make the results of the hand analysis correspond to online Bridge Designer, you must design it to scale.  If the angles are different, then the calculated forces will not be the same so it is important to make sure that the size of each member on Bridge Designer is to scale with the members of the hand analysis.
    This type of analysis is very helpful and can be used with our Knex designs.  By using the measurements of our design, we can determine the forces and modify the design accordingly.

A3-Truss Analysis: Amanda Ngov

By using the Method of Joint, calculations for an analysis of a bridge was possible. Figure 1 shows the calculations of a bridge that has a span of 24", a height of 8", and a load of 15 lb at the middle joint.

Figure 1

The diagram and table of all the forces can be seen in figure 2 and figure 3 below.

Figure 2

Figure 3

A computer program called Bridge Designer has the abilities to create a similar type of analysis of the bridge with similar values as seen below in figure 4. The advantage of this program is that it has the ability to scale the values of the length, width or load of any type of truss bridge. With this in mind, the bridge in figure 1 can be drawn twice as small or large. The only needed adjustment would be to multiple or divide the results outputted by the program. For example, if my bridge had a span of 48", height of 16", and a load of 30lb then all the forces would simply need to be multiplied by a factor of two. The F_AB would be approximately -18 lb instead of -9 lb. This basic concept can be applied to a number of different designs. In addition, the bridge in figure 5 has similar features of the previous truss design but with extra beam members. When the design was drawn in Bridge Designer, an error occurred because certain nodes were not attached by members. This resulted in an indeterminate bridge, which forced my group to adjust the design in Bridge Designer. In reality, the changes would allow a shift and more even distribution of the forces onto the other members. The overall forces are symmetrically and evenly distributed, but the forces in my group's design allows more even distributions.The advantage with recreating the design in Bridge Designer is simple scaling of the weight load or the length of the members to different proportions.

Figure 4

Figure 5

The knowledge of the "Testing Information About Knex Joints" gives knowledge on the average, median and minimum force (in pounds) a member would pull out from a joint given the amount of members that were connected. It appears that as the number of beams connected to a gusset increased, the load capacity increased. The reasoning and logic behind the results is the force can be displaced more evenly throughout the entire bridge as opposed to a few weaker beams. In addition, if a member got pulled out of the gusset, then other members have the ability to allow a longer period of time for the collapse of the bridge. A more graceful collapse will occur instead of a catastrophic collapse. In real life, a catastrophic collapse could result in many casualties dying. The process of this analysis has shown a more even distribution of forces is preferable for n efficient bridge.

Week 8: Team Update

The previous week students learned how to calculate the applied forces that are exerted on the beams and connection points of the bridge. After first students were given resources to watch a video on how the calculations were computed. In addition, students were able to expand the size of the bridge from two feet to the size of three feet. In general, the majority of students furthered their current design because it appeared to be the most efficient bridge at the moment. The calculations of the beams and connection joints were found and were computed by Bridge Designer. It can be seen below in figure 1.

The upcoming week will include new ideas on improving the bridge after the design have been calculated. Different angles, lengths of beams, and connectors will most likely be changed because students will gain more knowledge about bridges.

Some difficulties that will seen will occur when the forces of the bridge are being calculated. Human error could occur during the calculations. In addition, certain changes may not be possible to occur because certain materials are not readily available.

Week 8: Amanda Ngov

In the previous week, calculating the forces of bridges was the main priority to improve upon the bridge. My group accomplished two main tasks. First we extended the two foot bridge to a span of three feet. We decided to keep the overall design of the original bridge because it was extremely efficient. Changes are still needed to improve the bridge after  calculations are computed. The calculations to improve the bridge was also a major task that was required and accomplished in lab. Since the calculations were figured out, the next week will become easier in terms of knowing which aspects of the bridge need readjustments. Changes in angles, beam sizes, and gussets may be changed to increase the efficiency of the overall bridge. A major challenge that my group and I experienced was difficulties in the calculations. Uncertainty in how to calculate the forces of each piece in the bridge was different and uncommon because my group and I were never exposed to a task such as this. The video on the resource site did help in understanding the concept more.

The overall idea of the calculations has a decent approach to figuring the force load of the bridge, but there are other outside forces such as wind, earthquakes, and traffic. Considering the bridge to be suspended without any other type of loads the calculations are sufficient, but the purpose of bridge is to allow transportation of objects from one side to another though. With that in mind, the analysis is not sufficient for a real bridge. If granted, I would suggest that further knowledge of the geography of the location where the bridge would be placed is required to reinforce the bridge at the weak spots. An earthquake for example would exert great forces on the connection joints. Wind, on the other hand, would create more forces on the side of the bridge. More knowledge of the population around the area is also required because a large number of commuters would result in a large load of cars and trucks. The geographical analysis and population density of the area, in my opinion, are vital in creating the most efficient bridge.

Week 7: Corey Duane

          In week 6, the group tested their bridge.  In the previous week, the bridge was able to hold 36 pounds. Minor modifications were made to stop the bridge from twisting.  The modified bridge was able to hold 47 pounds.  A video was taking during the testing in order to capture the failure of the bridge.  After close examination of the bridge and video, it was determined that the bridge did not fail because of twisting like in the previous week, but it failed at the end points.  After the test, the group further modified the bridge by removing some members that had effect on the strength of the bridge, resulting in a decrease in the cost.
          A major benefit of West Point Bridge Designer was being able to see and recognize any weak points of the bridge with "block box".  This allowed for the designer to quickly modify the bridge and correct any weak points.  This helpful tool is not available with the Knex.  There is no way to tell which members are under the most tension and if there are any major weak points.  With the Knex, the only way to find out these things is to test it and exam the bridge once it has failed.

Week 7: Team Update

            In the previous week, the team was able to see the bridge in action. The bridge was suspended across a distance of twenty four inches. An apparatus was then placed through the bridge with a bucket of sand attached to its end. The bucket was able to be filled about three quarters of the way full. This in turn meant that the bridge was able to hold 47.8 pounds. After minor adjustments to week five’s design, the bridge design in week six was able to hold 11.8 ponds more than its previous design. The bridge did not break due to the weight of the sand; it broke because of one of the end points. With more analysis and a few adjustments, the team will be able to stabilize the bridge and allow it to hold even more weight. The bridge design cost $207,500 and had an efficiency cost of $4,341.

            Adjustments must be made to improve the stability and cost of the bridge. The removal of unnecessary pieces from the middle of the bridge, the cost can be reduced by at least $10,000. The team must also discover a way to keep the end joints from slipping out of place. Fixing these issues can cause the total weight the bridge can hold to increase and the price of the bridge to decrease. A lower price tag and greater strength and stability leads to a much improved efficiency cost.

            In the weeks to come the team must transform the bridge from two feet long to three feet long. The biggest challenge is going to be tweaking the design to extend its distance. Not only does the team need to develop a way to make the bridge longer but also how that will affect the end points and all of the weak points of the bridge.  

Week 7: Bridget Breslin

In week six, the Knex Bridge that was designed by the team was tested. The learned a lot from witnessing the bridge in action. We expected that the bridge would do fairly well considering it had done well in week five. In week five the bridge held roughly 36 pounds. Minor adjustments were done to the bridge to stop it from contorting and it was tested again in week six. The bridge broke not due to the weight but due to one of the end joints. The entire bridge remained intact except for the end point it broke at. Overall the bridge ended up holding 47.8 pounds of sand and had an efficiency cost of $4,341. With a few minor adjustments and the removal of unnecessary pieces the team could greatly improve the efficiency cost.

In West Point Bridge Designer, the team was able to view the weak points of the bridge with “block box” answers. This was extremely helpful when determining which areas of the bridge needed to be adjusted to make it stronger. When using the Knex to build the bridge, this feature is not available. Without specific numbers, it is more difficult to determine which regions of the bridge are under the most tension and compression. If these values were available it would tremendously help with bridge adjustments. Although the tension and compression of the bridge parts is not readily available, there are ways to calculate it. Drawing a free body diagram of the bridge could help to visualize which pieces are the weakest. Calculations from the free body diagram could then lead the team to determine the greatest tension and compression on the bridge.  

Week 7: Amanda Ngov What Want to Analyze

The previous week was an educational experience because the bridges were tested. Groups tested their bridges by adding sand into a bucket, that was suspended by an apparatus, until the bridge failed and collapsed. As the sand was being displaced as evenly as possible into the bucket, students observed where the weak points of the bridge were. For example, a specific bridge did not fail as a result of the weight of the sand but instead failed as a result of a weak beam without much support. Towards the collapse of the bridge, students realized the bending of a Knex piece was in a great amount of compression. One of the end points that acted as the reaction points was a weak point because of the high amount of compression force. The upcoming week will result in further improvements of the endpoints. In addition the bridge will span from two feet to three feet. This goal originated from the previous week's lab where students were able to gain knowledge in other designs' failures. Difficulties will occur when the span of the bridge is required to span a minimum of three feet. The challenge with this obstacle will come from the lack of knowledge in the field and the weak Knex pieces. 

The use of Knex pieces has limited the ability to know the compression and tension forces of each beam, the amount of weight a bridge can hold prior to testing and the amount of deflection the bridge experiences during a point load are the three major questions that are constantly asked to try to maximize the efficiency of the truss bridge. The amounts for these numerical values requires calculations that are currently unknown to many students, if not all, because students have not taken courses related to bridge design. 

Week 6: Bridget Breslin

In week five, our group was able to start adjusting the design for our bridge. We made minor but substantial changes to the bottom of our bridge. We used longer Knex pieces to allow for more bend in the bridge. We then had the chance to test out the bridge that we had designed. The bridge held thirty six pounds of weight and only broke due to contortion. Watching the bridge in action, gave me a better idea of how exactly our bridge was going to work and think about what should be changed in the design.

            After working more with the Knex pieces, my views of the similarities and differences between Knex and the West Point Bridge Designer program have remained the same. I still believe that the Knex give a better understanding than the West Point Bridge Designer of what to expect from the function of a realistic bridge. However, the Knex are more of a hassle when redesigning and readjusting designs.

            Even though Knex give more of a realistic approach, they do not completely portray the functionality of a real bridge. There would be many differences between designing a steel bridge spanning 20’ and a Knex bridge. The Knex pieces and pieces of steel have very different strengths and weights. The Knex joints are not completely secure whereas a steel bridge spanning 20’ would have more reliable and stable joints. For instance, as more weight is added to the Knex bridge, the grooved gusset plates detach and cause the bridge to collapse. The joints also do not secure the chords completely at every angle. The angles at which to work with using Knex are limited but in a steel bridge they can be created to an angle that is necessary. The Knex bridge is a good start to designing or developing ideas for a real bridge but is not completely reliable for a “real” steel bridge.

            I think the biggest challenge for the group in the upcoming week is going to be testing and readjusting the current design of the bridge. The current bridge design seems pretty stable however can always use more improvement.  

Week 6: Corey Duane

          The previous week allowed further work and design modifications to the bridge.  When testing the bridge, it was noticed that when it failed, it would fail at the connection points.  The idea of fewer connection points, the stronger the bridge was applied.  

This figure shows the latest design.  The yellow knex pieces along the bottom of the bridge were replaced with the longer gray pieces, decreasing the number of connections.

This figure shows the center of the bridge.  The weight in the center of the bridge goes directly down, and on the original design there was a connection there.  The connection would break because of the weight directly on it.  With this design, the weight can be evenly dispersed to all connections, making the bridge stronger.  

Week 6: Team Update

The previous week allowed many improvements to a bridge design, out of Knex pieces, because the majority of the lab was dedicated to allow students to experiment with different types of designs. At first, a basic yet expensive design with triangles and squares was created as seen in figure 1. 

Figure 1

This design cost over $275,000 and was weak at many connection joints. The cost was too extravagant which resulted in major changes to the basic geometric shape of the overall bridge. Different gussets were eventually discovered and acknowledged for different and unknown uses. The gussets that could be connected to similar gussets could withstand larger amounts of tension and compression forces. This resulted in an increase amount of those specific gussets in the design of the bridge. As the experimentation with the Knex pieces continued, new ideas and methods to increase the ratio of the cost to strength increased. The final design created can be seen below in Figure 2 after different gussets and ideas to lower the cost by changing the members was used and factored in. 

Figure 2

The upcoming week will have one major goal which is to further lower and improve the ratio for the most efficient bridge design among the other competitors. To have a functional truss is sufficient but will not win in a real life bid for a job or contract. This course shows how a real life situation can be applied to class modules.

Week 6: Amanda Ngov Knex Design and Build Process

Last week gave students a longer time frame of learning how to design and build a truss bridge with Knex pieces. The majority of the lab allowed access to all the available pieces for design changes and improvements as needed. In addition, the initial beginning of testing an intended finalized bridges was permitted and showed many faults in many bridges that students built. The main goal of the week was to lower the cost of the bridge. Consequently, some alterations were made to lower the cost of a specific bridge to around $200,000, from the extravagant original designed bridge of $260,000, geometric disfigurement and weak spots became visible in testings to show the group the features of the bridge that needed readjustments. The ratio of the cost and strength was much to large for a bridge to be called efficient; as a result, adjustments were made and will be continued to next week to make a better truss bridge. The upcoming week requires major changes and improvements in certain connection joints and more stability in beams, with the creation of triangles, to allow for an increase amount of compression and tension forces. Hoping to increase the overall strength of the bridge, different gussets will be used and more triangular shapes will be incorporated. Some challenges that were clearly encountered was the competition between other competitors. Other groups designed more efficient bridges. It was realized that certain smaller and shorter bridges designed were more efficient in cost and strength. New ideas are being designed and discussed about to improve the decent design already created. 

Reflecting on the past, it was noted that the computer program of West Point Bridge Design was more beneficial. Now it has been realized that the Knex kit is a much more realistic approach in the process of designing and creating a bridge. Although there are many advantages of the program as previously stated in last week's blog post, it has come to conclusion that the kit of Knex pieces has more benefits. The real hands on experience allows a more definite approach in the building process of a bridge. In addition, the limited amount of sizes allows a real world challenge. Real manufactures will not have every size of member beams or joint connectors available because they want to maximize their profitability. Consequently, the thirteen sizes represent the readily available beams or connections. In addition, an actual point and evenly distributed load test can be calculated and seen. Resulting from the two different test allows learners to see the failure points as well. These features mentioned cannot be applied or generated in the computer program West Point Bridge Design as well as the real life like experience with Knex pieces.

A2: Breslin

     The aim of this project was to build a bridge using different Knex pieces. Each piece had a different length and price tag. The goal was to construct a bridge that I believed would be durable and strong as well as low in cost. When designing the bridge I had come up with many different ideas but none that I thought would be constructed with a lower price tag. I had decided to keep the design simple and stick to basic concepts. Below is the design of the bridge I have created.

Bridge Design

Red lines represent 5" long chord
Yellow lines represent 3-3/8" long chord
Purple dots represent 180 degree grooved gusset plates

     Side View of Bridge Design:

     Top View of Bridge Design:

      Throughout the design process, my bridge design had not changed drastically. I knew from the start that I would like the bridge to take on the shape of a trapezoid from the side view. This aspect of the design remained constant throughout. Then next thing I decided was to add a series of right triangles into the side of the bridge. After completing the sides I determined that I would like to carry on the same idea to the top and bottom of the bridge as well. Over all I has used thirty-four 3-3/8” long chords, fourteen 5” long chords and forty-eight 180 degree grooved gusset plates. The price of the bridge design would cost a total of $175,000. Below is the Truss Bill of Materials which indicated the cost of each piece used and the total cost of the bridge.

     Truss Bill of Materials:

      After completing the design of the bridge I had learned many things. Developing an idea for a bridge takes a lot of time and effort. It is important to stick to simple realistic concepts and only get fancy if it is needed. Also building the strongest and safest bridge possible does not make it the most efficient. A bridge must have as much sustainability as possible with the lowest overall cost.

A2: Duane

          While designing the bridge, the group kept the constraints in mind-the bridge has to be at least two feet long and have a certain width.  The group began by coming up with a basic design and modifying it from there.  parts were added and taken off to build a stronger bridge.  

This figure shows the design in the first stage.  Once this design was complete, the group evaluated the bridge.  It was determined that the bridge would be able to hold a large amount of weight, however; the bridge would begin to twist.  

This figure shows the plan.  Modifications were later made to this design.  The width was shortened by replacing the horizontal pieces with shorter pieces.  This allowed for the truss design to be used on the top and bottom of the bridge, creating an overall stronger and safer design.  

This figure shows elevation of the design.  The one major design flaw is that the bridge begins to twist when under pressure.  This flaw was fixed by connecting additional pieces from one side to the other about halfway up the height of the bridge.  From this first design, the group has learned what works and what does not work.  The group further understands which pieces work best with others.

This is the Truss Bill of Materials.  As shown, the total cost of the design is $189,9000.  This cost will change drastically throughout the design process.  It will most likely increase because the group plans on adding more pieces to stop the bridge from twisting under pressure.  

Week 5: Team update

In week 4, the team applied the knowledge of bridges and their structure to create a model out of Knex. Before building began, components of truss bridges were reviewed and component cost and efficiency was discussed. It was established that the efficiency would be determined by the cost of the materials divided by the weight of sand the bridge can hold. This discussion was followed by information of how to research different bridge information and how information about past and current bridges could help to create better bridges in the future.

Although a distinctive design was not established the team is off to a great start. We were able to build an entire bridge out of Knex in the class time period. The bridge was developed using the idea to include large amounts of triangles. The structure of the sides was created to have the ends angled at 45 degrees followed by a series of right triangles.  The same general idea is carried out throughout the top, bottom and middle level of the bridge. These three layers are composed of a rectangle outline filled with right triangles. The overall price of the bridge is $253,500. This design for the bridge is a great starting point for the team. It allowed us to develop ideas and features that we would like to include in the final design.

Although a design has been created, more research and development is need for the bridge. The first design we come up with does not have to be our last. In the upcoming weeks, the team will be challenged the most on readjusting the bridge. The bridge needs to be altered in order to ensure that it remains or increases strength and stability while maintaining a low price tag. It will also be a challenge to fine a design to reduce the price of the bridge.

Aerial View of Bridge:

Side View of Bridge:

Week 5: Bridget Breslin

In the previous week, all of the information learned about the structure and development of bridges was applied. The team developed a bridge out of Knex. Initially, the concept seemed as if it would be extremely easy and a bridge would be completed in no time, however that was not true. When finally given the Knex, my ideas, as well as my teammates’ ideas, were somewhat limited due to the ability of the Knex pieces and the pieces that were available to us. After getting to accustomed what could and could not be done, a bridge was able to be built.

            The purpose of using Knex to construct a bridge is to get a more realistic understanding of the bridge building process. When using the West Point Bridge Designer program it was extremely helpful. The program helped to facilitate the thinking strategy of how to construct and design a bridge. However, the program had some flaws and in ways was not completely realistic, especially when it came to how an actual bridge would work in real life. The simulator did not account for outside factors and allowed too much bending of the bridge.

Transitioning to building a bridge out of Knex will help to get a better feel for what a realistic bridge could withstand. Like the West Point Bridge Designer, Knex help to get an understanding of the bridge design process, only with hands on experience. A Knex bridge that is built will not allow for as much bending and flexibility as the West Point Bridge Designer simulator.  Testing designs out of Knex and observing their successes and flaws will be more helpful to understand the successes and flaws in real bridges. Although doing this will be more time consuming because designing a bridge, testing it and claculating the price can not be instantly done by the program, it will take more effort.

In the upcoming week, I think that the biggest challenge is going to be perfecting the bridge. Although an initial design has been constructed, that does not mean it will be our final design. The team needs to review the price and sustainability of our current design and determine how to moderate it to make an even better bridge that is cheaper.

Week 5: Corey Duane

          Last week, the Engineering Librarian came to lab and shared resources that will be helpful in the future.  The librarian also went over how to efficiently use the Drexel University Library website.  Students were then able to begin using Knex to create and design a bridge.  Throughout the creating process, modifications were constantly brought up and made to the bridge.  The groups were permitted to take their designs from lab, however; the group did not take any additional pieces.  Next week, the group will have to take additional pieces in order to work on and make any necessary changes to the design.
          West Point Bridge Design seems more realistic.  The program show the specifics of each member used and it also calculates the total cost of the bridge design.  The Knex allows for more of a "hands-on" design.  Members can easily be taken off or added to the design and an actual 3-d model can be observed.  When it comes to changing the size of a member, using Knex, the designer has to locate a piece of suitable size which may not always be available.  On West Point Bridge Design, the designer has to simply draw a member that fits.

A2: Ngov

The essential reasoning of the design of a truss bridge with a Knex kit is to allow a hands on experience with a realistic approach for a creative design to be physically tested. Consequently, the pieces of Knex are being used. The design in Figure 1 and Figure 2 show the elevation and plan view of a specific designed truss bridge. The reasoning of this particular creation came about because the most cost effective and stable bridge created must be built for a competition. A limited amount of members and gussets were used because an excess amount of material will increase the cost dramatically; as a result, there were not a great number of Knex pieces used. In addition, the use of the triangular pattern and shape allows for maximum load bearing capacity compared to squares and circles.

A design of a bridge shown below is an example of a CAD drawing version of Knex of the elevation view.

Figure 1

The plan view of the design is shown below.

 

Figure 2

The spread sheet seen below shows the cost and materials used for the design. 

As the spread sheet shows, the cost of the bridge design should total to be approximately $189000. Only three main pieces were used. 46 3.375" long chords, 12 5.0" long chords, and 48 180 degree grooved gusset plates that were later connected were used to create the Knex bridge.

The original design of the bridge was hand drawn and needed to be completely redesign due to the limited amount of member sizes. In addition, the intended design began with more triangles intersecting the middle to reduce the amount of deformation of the squares because the geometry of squares will force the squares to become trapezoids under compression and tension. The amount of triangles was reduced because the cost of the bridge project was too extravagant. Consequently, the design seen in Figure 1 and Figure 2 were drawn up.

Throughout the process of designing this bridge, a number of things were taught. For example, the pieces are similar to real life were some pieces are readily available and made in industrial plants, while the customization of new pieces would have an extravagant cost. This showed that not every piece of member will be constantly available for the erection of a bridge. In addition, the planning and drawing of the bridge on a computer is a similar process to professional because real engineers and construction managers must have a clear understanding of other trades to complete a bridge. If a designer or any member of the project is unorganized or unable to communicate effectively, then misinterpretations will occur and the project will be prolonged; consequently, the cost of the project will increase while the productivity decreases.

Week 5: Amanda Ngov Knex Design

 The previous week had a number of questions answered because the Engineering librarian from Drexel University came to show a few resources that could be utilized for future references in the course project and future research papers for other classes. The navigation of the Drexel University library website was also shown for further understanding. In addition, the majority of the class allowed students to experiment and creatively design new ideas for a truss bridge with a kit called Knex. Though a final design has not been agreed upon, the progress of communicating ideas to other team members in a specific group is improving. Suggestions are constantly being offered and not enforced independently. For the upcoming week, the specific group hopes to accomplish a possible finalized design as a back up while creating new designs to improve on in the future with Knex. The main and only issue that the group is encountering is the inability to use or physically have more Knex pieces to experiment and design an efficient bridge. Permission was allowed to borrow pieces but only a few were taken. Next week, more pieces will be taken to create a great bridge. 

The use of the program West Point Bridge Design and Knex certainly showed a few similarities and differences. Firstly, the computer program allowed a stimulation of a load being suspended on the bridge that was recently designed to show the compression and tension forces in each member, while the Knex allowed a literal hands-on experience. The computer program also allowed for a number of variety and changes of the member's material and size, but the Knex does not allow a change because the alterations of the pieces will result in a break of the material. The West Point Bridge Design seems to be more realistic and suitable for the project occurring due to the additional amounts of benefits than the Knex pieces.

Week 4: Corey Duane

In the previous week, the groups were shown different designs of truss bridges.  The idea of changing the kinds of materials used in the design was also introduced.  The groups spent the lab designing different kinds of truss bridges through trial and error.  A final design for a truss bridge was not determined and further research should be done before making the final design is decided on.

The bridges are designed using a program called West Point Bridge Design.  This program allows the user to design a bridge using different kinds of materials.  The program determines the total cost of the design.  It also provides information such as the maximum compression force / strength, maximum tension force / strength, and the length of each beam used.  In the program, the user can choose between using carbon steel tubes, or hollow tubes.  Changing the type of material being used can decrease the overall cost of the bridge, but this also make the bridge less stable.  I think the program is pretty realistic.  It is able to calculate the cost of the bridge and some of the forces on it.  However, the program does not account for other factors.  When testing, one truck drives over the bridge, when in reality there could numerous trucks on the bridge at once.  Weather such as warm or cold temperatures, rain, snow, ice, and wind may not have an immediate effect on the bridge, but over time they do.  The program does not account for these factors as well.

Week 4: Bridget Breslin

In the previous week, the West Point Bridge Designer was used by the team, again. We had tested many different types of bridges in the program observing different factors. Designing a bridge that was as safe as it possibly could be was very important to us. Another factor we looked at was the cost. We designed many different types of trusses to try and make it as safe as possible at the lowest price. After many trials and errors, we then played around with using different types of materials for different components of the bridge. Doing this brought down the cost of the bridge substantially, however was more of a task choosing which pieces would be made of what material.  

After using the West Point Bridge Designer for several weeks now, I have noticed some qualities of the program that are not realistic. Although the program helps to facilitate the thought and design process, some designs would never work in real life. When the design for the bridge is completed, a test run is done, which is one of the problems in the software. No matter what the design of the bridge looks like, as long as it does not break or deform into so strange shape, the truck will pass over it. This is a huge problem because although the bridge is safe in the program, in real life it would be anything but safe. The program does not account for the proper amount of bending that should be allowed. Also, the program does not consider nature’s effects on the bridge. Finally, the West Point Bridge Designer does not drawn into account the fatigue on the bridge and how long it is supposed to last based on environmental conditions and usages. All of these factors need to be considered in real life, otherwise many lives will be at stake.