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

Week 9 - Bridge Process

Over the past 9 weeks, I have realized that my knowledge on Bridges and conducting analysis have expanded tremendously. I have become more familiar working with bridge design software such as WPBD and K'NEX to construct prototypes. Along with that, I learned to conduct truss analysis on the K’NEX Bridge by applying the “Method of Joints” and using the online software called the Bridge designer. The truss analysis enabled me to understand how tension and compression plays a major role in the designing process. Furthermore, I discovered that there are several factors that needs to be taken in to consideration during the designing process. The fact that attaching more membranes to the connectors increases the tensile pull-out force, changed my designing perspective. In conclusion, I learned the engineering aspects of Bridge Design process and understood the issues that will engage in the field of designing large structures.

During the previous week in class, our group remodeled the K’NEX bridge with the new set of constraints for our K’NEX Bridge. The Bridge redesigned to span 36 inches with a minimum width of 3.5 inches. From the information that was shown online, our group attached more membranes to the connectors to increase the pull-out force. To reduce the price, we also decided to replace the small membranes with longer membranes to reduce the amount of connectors. Our group conducted more forensic analysis and concluded that the bridge collapsed by being twisting. Therefore, the bridge went through more modification to allow the bridge to withheld twisting. This week in lab, we will be focusing majority of the time redesigning and conducting our final K’NEX Bridge test. 

Week 9 - Bridge Process

As the term comes to an end, I have gained significant knowledge on the bridge designing process. One very important and interesting concept I have learned about the process is how to analyze the forces applied on the truss bridges. One method we use was called “Method of Joints” to calculate the tension and compression on each membrane. Along with the calculation done by hand, “Bridge Design” automatically computes the values, which serves as a back up for the calculations. Finding tension and compression is very essential for the design processes to make an effective bridge. According to the values, I was able to make areas of the web stronger or remove unnecessary membranes to save money.

Last week in lab we were given the majority of the time to build the three-foot spanning bridge. We had to take in consideration the new constrains, such as the inside of the bridge has to be hollow by 3 inches wide and 2 inches in height. My group had most of the bridge created before lab so all we had to do was fix it a little and test it. During the test, our bridge held 26 pounds and collapsed by twisting. For the rest of the lab we finished modifying the bridge and made it ready for this week’s lab, where the whole class is required to do the final test.

A3 Sachin Patel

A3 Truss Analysis:

 Those were the pictures for my Calculations using the MOJ.

The force calculations done by the online simulator.

The online simulation for Our own bridge design. 

Analysis: 

 Using the method of joints on the online simulator helped us get realistic numbers for own own 

A3-JACOB

1.Calculations of forces in  the truss members using the Method of Joints.

Truss Bridge That was used in Method of Joints

Calculation of Forces via Method of Joints (MOJ)  - 1

Calculation of Forces via Method of Joints (MOJ)  -  2

Labeled Diagram showing results of MOJ.

2.Results of the Analysis

From the truss analysis it can be concluded that the members connected to the center node will have tension and the members not connected to the center node will have compression.

 3.

Bridge Designer Image Replicating MOJ

4.

The bridge designer is a very convenient method for calculating the tension and compression of each member in a Truss bridge design. The data collected from hand analysis and the online Bridge Designer is very similar. In order for both analysis to correspond, the length of the members and the angles must scale to each other. In Bridge Designer, each block represents 2 inches in length. Therefore, the ratio between the members must stay the same for the angles to stay the same. 

5.

Bridge Designer Applied to our Knex Truss

6. How to Use Analysis to Improve the Design of Knex Bridge

Using the method of joints analysis, we can determine a value of the tension and compression of members of the bridge for a given load. The testing information about the K’NEX rods and K’NEX connectors provides the tensile pull-out force for various modes of connection. The web page displays three different modes of connections that contain different number of membranes connected to one connector. Analyzing the tensile pull-out force, it is evident that the pull0 out force increases with the number of membranes attached to the connectors. I was also ale to observe that the pull out-force greatly increased going from Mode 2 to Mode 3 rather than Mode 1 to Mode 2. This Tensile pull-out force table is useful in understanding that the how the number of membrane to connector ratio directly correlates with the stability of the bridge. From this information, our objective for this week would be detected the weakest connections and strengthening it by additional membranes.

Week 8 - Analysis Process

The Method of joints is a nice approach to calculating the force load of the bridge. However, this method wouldn’t be sufficient for constructing a bridge in the real world. In a real world, there are many other forces that need to be considered such as the load of the bridge itself.  Method of joints mainly focuses on the forces going vertical, but in real world there are horizontal forces that impact the tension and compression of the members in a bridge design. Some of the other forces that can impact a real bridge would be the wind, location, weather and natural disasters like earthquakes. I would like to learn more about the each connectors and how the strength increases with more members get attached to it. I would also be really interested in learning about software like Bridge Designer that makes calculations more convenient.  

During the previous week in class, we discussed the new set of constraints for our K’NEX bridge. The Bridge is required to span 36 inches with a minimum width of 3.5 inches. Along with that the bridge must be a tube for the vehicles to drive across the bridge. Majority of the class focused on learning the proper method drawing free body diagrams, as well as calculating the forces using the method of joints. Method of joints can be used to calculate the tension and compression in the membranes involved in the bridge design. Using the calculated values, we can improve the design of our bridge. This week in lab, we will be conducting more truss analysis and finishing up the final design of the bridge.

A3 - Parth Patel

1) Method Of Joints

2) Results of Analysis

3) Bridge Design Replicate

4) Hand Analysis Correspond to Bridge Designer

          For the hand analysis to correspond with the Bridge Designer, the length of the membranes need to be scaled equally. In Bridge Designer, the length is contained and scaled to 2 inches per graphical unit, while on the hand drawing we can draw membranes at any sizes. Therefore, Bridge Designer needs to scale their bridge so the forces correlate with the values calculated.


5) Bridge Designer for Knex Bridge

6) Final Analysis

          According to the Knex joints test page, it shows that it requires more force to remove a membrane from a 180 gusset plate as the number of membranes added to the gusset increases. Using the given average pull-out force for the different types of modes, such as one, two or three attached membranes, we can compare it with our Knex truss bridge. The online Bridge Designer has already computed the values of forces applied on each membrane of our bridge; so now we only need to identify the membranes close or far from the maximum limit of force. Than we could adjust those certain membranes to build a better cost to weight ratio bridge. For example, if a membrane if suffering force close to its maximum capacity, we can add more membranes in that region, such as to the gusset plates to make a stronger bridge. Similarly, if a membrane is suffering very few amounts of force, we could take the piece out and reduce the estimated bridge cost.

Week 8 - Analysis Process

      In my opinion, “Method of Joints” for analysis is not sufficient enough for a real bridge in a realistic situation. First of all, the load applied on a real bridge is different than the situation we considered for class where it only has vertical force. A real bridge will have force from all directions, for example the horizontal load from wind. Also the size and type of membranes included on a real bridge will contribute to how much load is actually felt on the joints. Another factor is the constant change of load applied on a real bridge, such as number of vehicles or weather patterns. Therefore, there will be a constant variation of forces applied on each membrane and joints.  In addition with “Method of Joints” I would also like to know the strengths of each membrane and joint so I could predict at which forces will the bridge collapse due to the specific parts. One more think I would like to analyze is the failure of the two 180 grooved gusset plates because they are found to be weak and caused our first bridge to easily collapse. 

       Last week in lab we discussed how to analyze the forces applied on a bridge by using the process called “Method of Joints.” With this method, students are able to learn how to compute tension or compression forces felt on each membrane of the truss bridge. This mathematical tool can help students compute the forces applied on their Knex bridges and make adjustments for a better result. For example, if certain membrane is experiencing a great amount of force, the best method is to make that area strong and compatible for the load applied. This week in class we will finish designing a truss bridge that will span over 36 feet and follows the new constrains. This will be the second bridge that the students will be testing in class. 

Week 7: Analysis Desires

One of the differences between WPBD software and Knex is the “Block box” answers. The “Block Box” provided with values associating with compression and tension of each membrane of the bridge design. These numeric values were very useful in terms of studying and understanding the strength and weakness in the design of the bridge. In addition, the software highlights the membranes that failed the bridge after each load testing. These were great beneficial features because it allowed us to analyze our bridge design effectively. As a result we were able to construct a serviceable bridge design that satisfied all the constraints and remained in low budget. Working with Knex would be more resourceful if there was a system to calculate the tension and compression of each membrane as it goes through the load testing. I would recommend using the VideoPoint software which can be used to record the testing and analyze the footage. VideoPoint with VideoPoint Capture allows you to gather position vs. time data of a QuickTime movie. The collected data can be viewed in a table and plotted to examine the design of the bridge.

During the previous week in class, our group was able to make little modification to the original bridge. While we modified our bridge, we were quickly able to come to a hypothesis that our grooved gusset plates and the long chord were worn-out from constant remodeling. From the testing we were able to conclude that our bridge design was very weak because it was only able to hold about 5 pounds. During the class discussion we were very interested by one of the groups who decided to design a bridge without any grooved gusset plates and produce good results. Therefore, we decided to redesign the bridge by completely replacing the grooved gusset plates with other connectors. This week in lab we will conducting more truss analysis and learning about the joint method and the importance of free body diagram.

Week 7: Analysis Desires

If we were able to get a analysis of the our KNEX bridge just like we got in WPBD, I would be able to tell what exactly is the problem with the 180 groove gussets. Like in WPBD, I wish I was able to see what the most strained or least strained pieces were, which pieces had the most tension in them, so that we knew how to change our bridge with a better perspective. Though we would not how to do further calculations with these numbers, since we have no prior background, but if given formula's, finding out more in depth analytical numbers would be greatly appreciated. But, for now we have to make best use of our eye, trying to watch each piece as more and more weight is put onto the load, if we are sucsessfully get three good angles at the bridge, we might have a good chance of seeing where out bridge exactly failed from.

Last week the entire class performed loading tests on our bridges. We came out with a lousy and pathetic 5 lbs. we partially knew that we would score low because of the 180 groove gusset plates that we used. Yes, they added a versatile part to our bridge, but in the end it was just too weak of a part. We did not just have once of them our every gusset plate on our bridge was that one, which amplified the instability of our bridge even more. This week we hope to construct an entirely new bridge that holds alot more than a measly 5 lbs.

Week 7 - Analysis Desires

West Point Bridge Design provided very useful feedback such as the tension force and compression force for every beam and gusset point. The numeric information helped students understand their bridges better; areas that are over strained or less strained. With this resource I was able to change the design around and try different methods to find the lowest cost to strength ratio. Unfortunately, Knex does not provide numeric feedback but allows student to visually see how the bridge fails. This allows students to observe the effects of different weights and points of the bridge where it collapses. However, with numeric information for the amounts of forces applied at various points of the bridge could help me understand better how the bridge fails. For example, if the tension on a certain beam is high, I would change the design on that area to prevent it from collapsing. Vise verse, if the tension on a certain beam is very low, I would try to parts out from that area so it can reduce the total estimated cost. Unfortunately, I have no previous idea or research for how to calculate these numeric values.   

Last week in lab we had spent a long period of time testing the bridges created by all the groups. My groups bridge resulted in a epic failure. It was completely unstable, unreliable, and only held a little over 5 pounds. My group had already anticipated a bad result before the test because we recently realized that the 180 groove gusset plates are extremely unreliable to use as connectors. The two combination of two 180 grooved gusset, which was used numerous times in our design, easily separated even without a lot of weight compressed on it. Unfortunately we didn’t have enough time to change our design and had to face the failure. However, my group has acquired significant knowledge from the failure to be able to build a better bridge. This week in lab we will learn how to analyze bridges and calculate numeric values, which will also help to design a stronger bridge for the week 8 test.  

Week 6 KNEX

Working with the KNEX for a week, I have come to the view that KNEX are alot better with building bridge. 

It gives you a wide range of connectors and different types of rods. With the KNEX we are actually able to test out out bridges, so the relativistic effects on a bridge are seen. the uneven weight distribution is put forth in front of you, unlike WPBD the full range of those defects are not seen. Here you are clearly able to see what connectors are bad and which are good. So that you know exactly which parts to replace and which to keep and where to change the structure of bridge if need be. Which WPBD did not show connector defects, it only showed uneven distribution in the rods. So, maybe changing a connector was not an option. Here it is, which also may keep cost down, since you are able to change a broader range of items. 

This week we will be testing the weight capacity of out bridges with sand, as well as the discussing and changes that might be needed to out bridge. We have done several modifications so far but our bridge still had about the same strucuture, a trapezoidal prism. This week we need to fix all of our connector issues that were presented to us last week. 

Week 6 - Knex Process

After working with the Knex for a week, I have noticed that my previous perspectives of the comparison between Knex and WPBD have slightly shifted. I have noticed that working with Knex gives you more options to design your bridge. Especially the connectors, WPBD is limited to one type of connector while Knex has variety of connectors. In addition, Knex consist of groove gussets that can be attached another groove gusset to strengthen the bridge. Some of the major flaw in the similarities and differences I had previously seen between Knex and WPDB programs is with testing the bridge. WPBD program provides a constant result because the bridge is being tested in a controlled testing field. The results from the Knex bridges can vary because the bridges are tested at an uncontrolled field. Therefore other factors can influence the end result of the bridge such as the position of the bridge and the placing of the weights on the bucket. Another discovery I made from working with the Knex was that the connectors and the chords starts to bend and becomes less stable, more we work with the Knex. Whereas, the joint and the membranes in WPBD programs remain stable and unchanged as they undergo more testing.

During the previous week in class, our group discussed about the design that will produce the most efficient bridge. For the rest of the class, we worked with the Knex to build one bridge as a team. We did several trial and error on our own and modified the design as went along. Although our bridge went through several modifications, the basic outline of the bridge remained as a trapezoidal prism. For the next week in class, we will be discussing the construction issues and conducting more Knex bridge testing.    

Week 6 - Knex Process

After spending another week with Knex to build a bridge, I believe that it is harder than I first assumed. First of all, it was difficult to choose which design or method the team will use to create the bridge because there are numerous different options. In addition, while building the bridge we encountered several problems, such as the parts not fitting with the design due to the limited sizes available. As we moved on fixing the problems, at the end it resulted with a very expensive bridge. The most important observation we saw about the Knex pieces is the 180 groove gussets. The most common procedure is to combine two of the 180 groove gussets to able to create a rectangular prism structure, but it turned out to be very expensive and unstable. Our bridge, which contained numerous 180 groove gussets, was extremely weak and unreliable even though it was expensive. Therefore, it is very important to understand all of the Knex pieces and use them efficiently. In West Point Bridge Design, all the parts played similar role, but the gussets were not as important as they are in Knex. In addition I realized that in WPBD, increasing the cost will increase that strength ratio, which does not occur with knex pieces.

Last week in lab, the groups were allowed to build a bridge based on their design from the A1 assignment using Knex pieces. My group decided to build one bridge as a team effort and incorporate everyone’s ideas. Our bridge was structured in a small rectangular prism with triangles as the web. It contained numerous pairs of 180 grooved gussets, which turned out to be unreliable. This week in lab, each group will test their final outcome of knex bridge and try to analyze how it fails.

Week 5: WPBD vs. KNEX

In the last weeks class, we started to build a truss bridge of our own with the KNEX. Unlike the weeks prior to where we used the WPBD. Both ways a vastly different from each other, one it utilized on the computer and the other is hand made. Therefore calculations on the bridge are alot harder when done by hand. Therefore alot more time consuming, unlike WPBD that would run throught the calculations in a second.

Unlike WPBD with the KNEX we were able to do anything we felt. We were not limited to gusset constrains even though there were other constraints. Also building the bridge by hand gives us a more hands on approach to the actual things physical factors that affect the bridge and its sustainability over time.  Once we get a grasp on the how the bridge can be affected, we can build a stronger bridge. Unlike WPBD that did not tell us how the bridge had uneven weight distribution, we simply just swapped a pipe out to make it stronger, not knowing exactly how it did so. 

In the end both ways are excellent on their own in the process of bridge designing, but with the combination of both, one is able to get a full novel grasp on bridge designing, although it seems for practical for us to learn with the KNEX first to get a grasp, then build with WPBD.

Week 5: WPBD - Knex

During the past weeks, the students have been introduced to two different methods of designing and constructing a truss bridge. Although there are similarities in the two methods, each method demonstrates different aspects of engineering. The West Point Bridge design software allowed the students to comprehend the mechanism involved in designing a truss bridge. Similarly, designing the bridge using Knex provided the students to visualize the structural behavior included in the designing an actual bridge. Along with that, both methods express the budget factor that plays an important role in the designing process.

The major difference between these two methods would be that West Point Bridge Design software has a limit to the types of gussets used to connect membranes while the Knex method limits types of materials and their thickness to construct the bridge. In my perspective, WPBD software is very time efficient and more convenient in regards to restructure and rearrange the design of the bridge calculating the cost of the bridge. The software also allows the students to quickly calculate the cost of the bridge, while the Knex method requires the students to calculate everything using excel file. In addition, the Knex method provides more hands on experience the assembling of the truss bridge. Overall, both methods serve as a great guide to comprehending the engineering aspects convoluted in designing process.

During the previous week in class, we discussed the constraints that need to be considered in building the final design. We also received an overview of the assessment that each bridge will have to undergo during the final week. For the rest of the class, the group decided to work together in designing a “real” truss bridge using Knex. For next week, each group member will have a blueprint of their own unique design including the details of materials involved in the construction.

A2-JACOB

Bill of Materials

Elevation Image

Plan Image

My initial objective was to construct a truss bridge that satisfied all the design constraints and had the best price to weight. I realized that the best way to start the design is by applying what I learned so far. Therefore, my objective shifted to building the simplest design with smallest membranes that followed the same truss pattern as the one I designed on the WPBD software. To build 8" wide flat portion on the top of the bridge, I decided to remove the arc that I previously designed on the software. My initial designed consisted of blue and white long chords because I recognized that shorter beams are more stable than longer beams. My initial design of the bridge was expensive and totaled over $350,000.   During the designing process, I was able to cut down the price significantly. I recognized that one yellow long chord going diagonal was efficient and cheaper than having two white chords connected with a gusset plate going diagonal. By replacing the white chords with one yellow chord enabled me to lower my price range to $277,500. The basic outline of the bridge didn’t experience any change and remained as a trapezoid with the long base that spanned 2 feet and 1/8 inches with a height of 3.125 inches. This assignment was a great learning experience as well as a great hands-on experience on how real designing work. The assignment also taught me the importance of making accurate measurements and keeping a record of the progress of the design. Overall, this assignment was a great way to understand the engineering aspects involved in designing a bridge.

Week 5: WPBD - Knex

After Transitioning from WPBD and into Knex for designing a bridge, I realized that WPBD is much easier and different than Knex. In WPBD we did not have to face problem with dimensions or the materiel size. Students were allowed to create beams from any point to another point and than allowed to just test the bridge to observe the results. With Knex we only have few options to choose from to bulid our bridge and also have to take in considerastion which part fits with other parts. For example, depending on the outer frame of the bridge, only a certain bars or design can be used to create the 'web'. In the Knex's kit we have to choose from the different collored beams accoriding to size, such as white, blue, yellow, red, and gray; in addition with the types of gussets. The main difference between WPBD and Knex is the lack of helpful feed back WPBD provided on the tension and concentration or each material.Both West Point Bridge Design and Knex are excellent tools for engineers to understand how professionals design real structures. It is a tool that helps visualize structural behavior and also an opportunity to experience the design process.
  
Last week in lab we were introduced to Knex and allowed to play with them get a good understanding. The first thing done was a presentation which gave details and constrains for the bridge competition. I was able to realize what my bridge needs to accomplish and how it should be design to meet the constraints of the competition. Furthermore, the presentation informed the class about the different Knex parts and how much each will cost. At end we were allows to play with the Knex to get a good feel of how the bridge will be. This week in lab we will work more with the Knex pieces and attempt to Build a bridge for the competition.

A2 - Parth Patel

 

 My idea for designing the bridge is to use small pieces, such as the blue and white beams, so that I can  include more numbers of pieces for a low estimated total cost. My design contains square cross sections, which holds triangular webs to provide the strongest support. Design 1 contains a strong web, but is a expensive bridge while Design 2 has weak webs for a low cost. During the designing process, I changed various aspects of the bridge, such as making the bridge smaller by using the blue bars instead of yellow bars for the outside frame. In addition, I changed the design of the web several times in order to create a very inexpensive bridge. In conclusion, I was able to receive experience on how to use the Knex pieces to design a bridge. It was a very good experience because it was much different than using West Point Bridge Design and required more critical thinking. In addition, I learned how to design a bridge by keeping the cost in consideration, which will be of huge importance during the competition.