Week 10: Term Review

Last week in class we tested our final bridge designs. The new three foot bridge we constructed was 395,500 dollars and held 31.8 pounds. We had predicted that it would hold at the least above 25 pounds, because we took a estimate according to how much our 2 foot bridge held during the second round of testings. After a quick calculation our bridge had a $12,359 per pound cost to weight ratio. In week 10 of class we will we reviewing what we had accomplished in the past 9 weeks of lab.

Putting the last 9 weeks into perspective, I have learned a lot of new skills and refined a few others. My analysis and design skills have definitely been improved. This was mainly accomplished by the MOJ and the bridge weight testing that we had done in class. Seeing where the bridge failed, I was able to analyze where the bridge needed to be modified, and modifying the bridge helps immensely with the design process.

There were a lot of things that were beneficial to the class, and I felt added alot of knowledge to each individual student. Be the student a mechanical, architectural, civil, biomedical, engineer, the aspects of the design and analysis process we were taught by Professor Mitchell we unparalleled. We learned new concepts, like tension and compression, tensile strength, concepts that apply to almost all engineering fields. But, I feel the class as a whole would have learned more, if we learned a few more analysis skills, so that our bridges might have turned out better.

Week 10: Term Review

Week 10-Term Review

During the previous week in class, our group conducted our final testing for the K'nex bridge design. Using the excel spreed sheet, we calculated the bill of materials for our final bridge to be around $ 395,500. From previously conducted testing and analysis, we predicted that the bridge would uphold more than 25 pounds. Our bridge satisfied our prediction and was capable to uphold 31.8 pounds. We concluded that our bridge design was able to provide a reasonable cost to weight ratio of $12,359 per pound. This week in lab, we will be reflecting upon the materials covered and learned throughout the entire term.


As the term comes to an end, I realized that I have been able to accomplish many things both individually and as a group. Each week was a new learning experience and discovery to a new aspect of engineering that I was unfamiliar with. Some of the notable accomplishments include being able to conduct Forensic analysis, Truss Analysis, Computer modeling, Drafting Plan and Elevation Drawings. There were several challenges that was encountered during the learning process. As a group, we were able to overcome these challenges and improve our project. 


In my perspective, I would consider the least beneficial to be the Bridge designer. There were several constraints that needed to be satisfied for the program to calculate the tension and compression on the membranes. These constraints limited the amount of nodes to amount of membranes which made it impossible for my group to mirror our design into the program. However, the program allowed me to understand the importance of tension and compression in the design process. Conducting the actual testing was the most beneficial in terms of improving the design and the cost of weight ratio. My only suggestion would be to provide the students with more time for the physical testing of the K'nex bridge. I would recommend this course to any engineer seeking a career in the Civil and Architectural Field. Overall, the course was well organized and provided great knowledge to the engineering aspects contained in the innovating process. 

Week 10 - Term Review

    After completing this full term, I realized that I have significantly learned more than I had initially predicted before starting this course. I have gained vital and noteworthy knowledge regarding the engineering aspect of designing process. The most important goals of the courses that I agree with is planning, designing, modeling, and analyzing. To make a successful bridge, I was required to put intensive planning and testing, which continuously changed as I learned new concepts every week. It was also helpful and interesting to model different types of bridges, such as knex for physical models and West Point Bridge Design for computer models. In addition, we spent time learning how analyze the effects of loads on bridges like real engineers would, for example the “Method of Joints.” Unfortunately,  there are some goals that I do no agree with for this course. First of all, this project barley required any teamwork, for the bridge design and website assignments.  Most of the work was considerably easy and possible to be accomplished by one person alone. Therefore, I believe this project should not be considered to be a topic for ENGR-102 because it is scientifically unproductive and easy compared to the NXT Robot module. In conclusion, this project was beneficial for me learn how to plan and use analyzes to make a effective design. For future references I would recommend making students do more types of analysis and add more constrains on the bridge to make the assignment difficult.

    Last week in lab we had tested our final knex bridge, which spanned 36 inches and had the new constrains. Our bridge exceeded our expectations and uphold 31.8 pounds, with a reasonable cost of 359,500. The bridge failed in the area between the center and right end of the bridge, which we did not expect. This week in lab, we will briefly summarize everything that we covered and learned during this course.

A4 - Parth, Jaimon, Sachin

1. Background

•     In ENGR bridge design, students received the opportunity to explore and practice the design process of large projects; which could be bridges, buildings, highways, etc. The goal of the course was to have student understand and experience the process of working in team, planning, documenting, modeling and analyzing. Through these goals the students receives a better grasp of how engineering uptakes in the field. The most efficient method of any project is to create prototypes or smaller scale of the structure and conduct analysis from the testing results to make improvements to the project.  Therefore, the students were assigned  several checkpoints throughout each week that needed to be satisfied to proceed. These checkpoints introduced the students to various  such as West Point Bridge Designer, Bridge Designer, and K'nex pieces and allowed them to experiment their prototype of the bridge design.  The ultimate task for the course was to work in a team to inquire the best solution for the problem given a set of constraints. Constraints such as building and testing  a serviceable K'nex bridge that spans a certain length, width and height. During the whole process, students were able to expand their knowledge on the various physical properties and concepts related to the designing process of truss bridges. 

2. Design Process

• Our primary objective was to construct a simple truss bridge that satisfied all the design constraints and had a best cost to weight ratio. First we utilized West Point Bridge Designer to design a bridge, and it made all of the calculations for us. Therefore, the designing aspect was easy, we just had to make sure to, counteract the tension and compression on the bridge chords. Then the task was to make a bridge using K'nex pieces, which took a hands on approach. This time the bridge will be evaluated based on the price of the bridge and the weight it could withstand. As the course progressed, our group was introduced to various tools and more knowledgeable about the designing process.  Our initial bridge that spanned 24'' constructed using the blue membranes was only able to withhold  five pounds. During our Truss analysis we discovered that by increasing the number of membranes and decreasing the amount of connectors will increase the tensile pull-out force of K'nex rod from a K'nex connector. Next, we learned about the "Method of Joints" (MOJ), system that calculates the exact tension on our bridge. Therefore, for our final design we chose to replace the longer membrane which will result in less connectors and still satisfy the new set of constraints. The predicted load of failure was 26 pounds. This was calculated based upon the testing results conducted by truss analysis conducted each week. 

3. Description of Final Bridge

 The Bill of Materials

Elevation View

                                                        

Inside View

Plan View

The final design of our bridge cost $395,500 and consisted of 265 K'nex pieces. The bridge design met all the required constraints.






4. Testing Results 
    a) Load at Failure

•         The Bridge was able to upheld a 31.8 pound load.

    b) Describe the failure mode of the Bridge


     Our Bridge exceed past our expectations and held more load than it did during the first testing period. We initially believed that the middle section of our bridge was extremely strong and our fail towards the end points of the bridge. However, it actually failed due tension more towards the center of the bridge, in between the center and right end point. 

The failure mode of the bridge

5. Conclusion 

•      In conclusion our bridge exceeded our expectations and held a excellent amount of 31.8 pounds when we only guessed 26 pounds. The final bridge design that consisted of 265 K'nex pieces resulted in a cost to weight ratio of around $12,437 per pound. Unfortunately, we lacked in our analysis and predicted the method of failure wrong for the final bridge. The mode of failure was the separation of the 180 gusset and the yellow membrane. The bridge failed gracefully without pieces exploding everywhere. This demonstrates the strength of the bridge design. Overall, it was a great learning experience and also gave us a good opportunity to perceive the engineering aspects on designing process. It was a good insight for our future engineering careers.  

6. Future Work

•     For our future bridge, we would primarily attempt to bring the total cost down by using less numbers of pieces. Also try to use less of the red beams, which costs 2,000 dollars each. Overall, we believe that our final design has a effective structure and contains all of our best concepts. Therefore, we would not change much of the bridge, besides manipulating the pieces to reduce the total cost.

Bridge Process

Over the last few weeks I have learned alot from engineering lab

Week 8 - Bridge Testing