Nilay's Posts

Week 9

During week 9 we tested the final 3 foot bridge that we designed as a team, and spent the rest of the time in taking apart the bridge parts and returning them to their appropriate containers. We also briefly looked over the deliverables for A4 in case we had any questions about it. The major accomplishment was that we successfully finished the bridge module without any issues. During the next week we will be working on A4 which will be the last assignment for this class. We did not have any major issues throughout the term.

Looking back at the bridge module, I learned a lot from each of the goals identified in the course description. Teamwork was almost integrated throughout this course. Each of the bridge projects helped me learn the process of planning, documenting, design process by which the design undergoes modifications, computer modeling and physical modeling. I also learned forensic analysis through the actual testing of the Knex bridges. Static analysis gave us the basic knowledge on how to calculate forces on individual members which would be similar to any large scale bridge projects. To accomplish all these tasks, we used a variety of software that I had never used before, but certainly gained efficiency in using them upon finishing this term.

 All the goals taught something to us, but based on the area of engineering I am planning on concentrating, the bridge analysis was the least beneficial for me. The specific analysis of the bridge did not serve much help, but the overall idea of analyzing something in detail would certainly apply to most of the engineering disciplines. The most beneficial aspect of this course was the teamwork and design process. Again, those two things are something that applies to all the engineering fields. They taught me how to work efficiently with others, and how to make changes to a product while designing it. For future, I would substitute one of the Knex bridge assignments (2 feet or 3 feet) with something different. 

Week 8


During the 8^th week, we worked on designing our new bridge that has to span 3 feet. We tried a few different side designs to see which one we felt most comfortable with. We built the bridge based on the design we thought was the best in terms of its weight holding capacity (as predicted) and the price. We then tested the bridge using the parameters we will be using in the next week for the official testing of the bridges. It was able to hold decent amount of weight on the first try (about 25 lbs) so we decided to reduce its cost by removing some of the members connecting the two sides of the bridge. We tested it again but the amount of weight it held dropped significantly. So our plan for next week is to re-design the final bridge that can hold decent amount of weight without failing which we will be test during week 9. The only accomplishment this week was to test the same design with different number of members connecting the two sides of the bridge which gave us an idea on how much the connecting pieces contribute to its weight holding capacity.

We have completed almost 9 weeks of the bridge module which has brought many new things into my perspective. I learned quite a few things from the bridge design tools such as WPBD, Knex, truss analysis etc. that we utilized throughout the term. One of techniques I learned in designing a bridge when our goal is to have the lowest cost is that you can analyze the compression and tension forces using WPBD and try to reach the ratio of 1. This can be done by using different variations throughout the bridge which include changing the member size, material and length etc. while reaching a ‘functioning’ bridge. However, in real world, the bridge would be undergoing a lot of external forces such as wind turbulence etc. The amount of force applied by the vehicles travelling over the bridge would also vary constantly. So to ensure the safety, the bridge would have to be designed such that it can withstand the maximum amount of force. Every members and gusset plates would have to be analyzed in great detail to ensure that they wouldn’t give up under the normally expected force. In this case, the safety would be the first priority, not the overall cost of the bridge.

Week 7

During week 7, we briefly looked through the assignment 3 deliverables which asks us to perform a simple truss analysis on a 7 member bridge. We also browsed through the accompanying video which showed us how to perform the calculation to make sure we understand everything so we can ask questions to TA if something was unclear. Our group planned on doing the actual assignment outside of class in an environment where we could hear the sound of the video better without disturbing others around us. We then spent the remaining period of the class in brainstorming ideas for our next bridge. A major accomplishment for this week would be analysis of the sample bridge as well as our own bridge using the Bridge Designer software. While Knex does not provide us with box answers for the tension and compression forces, this method certainly helped us by giving us some ideas about the forces acting on the members of our bridge.

Using Bridge Designer software for the analysis only gives us a rough idea about the forces acting on the bridge. These forces are calculated without taking into account the weights of the members. While in real world, the weight of the members would play a crucial role. The force of the load is directly applied at a single point (center) in the Bridge Designer, while in real world the forces caused by the live load would be under constant change as vehicles move across the bridge. In real world, external forces such as wind affect the total forces acting on the bridge, which is not a parameter for Bridge Designer. As far as the Knex bridge is concerned, it would be helpful to know the magnitude of forces that cause the joints of the members to the gusset plates break.  

For the coming week we plan to analyze the Bridge Designer results in order to help navigate our design process in making a strong and cost efficient bridge.  

Week 6

Major portion of this week’s class was used in testing the bridge designed by our group during last week. We made some final adjustments to our design by changing the gusset plate connections at a few of the joints. The test parameters included a 2 feet span where the bridge would be suspended with a bucket hanging from the center. The weight was added in the form of sand which allowed us to get an accurate weight at which the bridge failed. Our bridge, which cost us $124,000 held 24.8 lb, resulting in a decent cost to weight ratio. However, the group was disappointed since we were expecting it to hold more than 35- 40 lb. Testing our bridge serves as a major accomplishment since we were able to see the failure points of our bridge. This design, like most others, failed at the joints. None of the parts actually broke, but the joints gave up due to the force and separated which caused our bridge to collapse. Next week we plan to make improvements and changes to our design for the next one which will be spanning 3 feet.

WPBD readily provided us with the tension/compression forces acting on each individual parts of the bridge which served as a big advantage. It allowed us to decide which parts should be compromised in terms of the material used to reduce the cost. Knowing the forces acting on each part, specifically gusset plates would allow us to design a stronger bridge. Gusset plates seemed to be the most common cause of bridge failure, whether it be through physical breaking of the part or through the separation of joints. The members seem to be very strong and don’t usually break. So knowing the amount of force acting on each part would tell us which portions of the bridge are most crucial. This would allow us to decide upon the type of joints we can use for different parts of the bridge. 

Week 5

During the fifth week we worked on our group bridge design. We started with three individual designs, and went with the one which seemed the strongest. We tried adding and subtracting minor, different variations to that design until we settled upon one. We tested our bridge in class so we can notice the weak points and try to improve on those areas for our final group design that we turn in for the competition. Major accomplishment for this week is that we have the general idea for the design of our bridge. Our plan for next week is to build the final Knex bridge that will be turned in to compete against other bridges. We did not finish calculating the cost of our bridge so that’s a task for next week as well. We are standing at a good position right now, and don’t have any issues.

My view on the similarities and differences between WPBD and Knex hasn’t changed much at all. Knex only provides us with one material for the bridge, but has different lengths and gusset plates.  A couple of things would have different considerations if we were to compare the Knex bridge model with a real steel bridge spanning 20’. For the real bridge, we would have options for using different materials for the chords and the web members based on the amount of force/load each has to bare. Knex, as mentioned above, only provides us with one type of material. We would also have stronger joints at the gusset plates in the real bridge since we would be able to weld it in place. On the other hand, Knex connections are really “welded”/ held together properly, which is a main reason for the Knex bridge to collapse. The chord pieces in Knex don’t usually break, proving that they’re able to withstand a lot of force before they break at the joints. We would also need to build a base for the real world bridge whereas we don’t build one for the Knex model. 

Week 4

During the fourth week we had a presentation on the Knex bridge assignment which laid out the goals and objectives in detail. It objective is to have the cheapest bridge and possible which can withhold the maximum weight. So our goal is to reach the lowest numbers possible when the cost of the bridge is divided by the weight it holds at the failure point. The price for each Knex parts was laid out in the presentation as well. We also had a brief presentation from Mr. Jay Bhatt who introduced us to engineering specific database and sources. The remaining time was spent familiarizing ourselves with the Knex kit, which can be considered as one of our major accomplishments since we will be using them for the rest of this term. Next week, we will be building our individual bridges based on the design that we proposed. There are no major issues that we face right now. However, I don’t have any past experiences with Knex and as a result the bridge I built in class failed at the joints upon applying pressure. So part of my challenge is to experiment with different joints until I reach a sturdy one.

As we move from WPBD to Knex, I can point out some similarities and some differences between the two. They’re both limiting in the variety of ‘material’ they provide us to use for the bridge. Also they both let us built and analyze the bridge but they do not include the labor cost. This is a crucial component since our overall goal, in both the cases, is to have the lowest cost. One major difference between the two is that WPBD exaggerates the weak points of the bridge in the animation and also calculates the different forces acting on different parts of the bridge, allowing us perform several tries on the computer until we reach a functioning model. Knex model on the other hand is physically tested and it does not provide us with electronically computed data. We would have to compute the forces ourselves and rebuild different designs to reach a better result. In WPBD our goal was to design the cheapest bridge possible which is capable of moving the truck across; thus the weight load had a limit. With the Knex model, we have to design the cheapest bridge that can support the maximum load until its failure point.

Week 3

During the third week, the class had a brief discussion about the different factors that would be considered during the construction of a bridge. For example, the cost of the bridge wouldn’t be the only thing that people would care about. Other factors like the life span, weight holding capacity and the look of the bridge also come into consideration. We also reviewed the comp1 results where the costs of everyone’s bridges were compared with the depths. We further saw the design and animation of the cheapest bridge, priced at about $222k. The rest of the class period was spent collaborating with our group to combine our ideas in order to build a better bridge. We followed our initial arc design and did not take symmetry/ looks of the bridge into account since our goal was to design the cheapest bridge possible. We managed to design a functioning bridge at a cost of $221k which is one of our major accomplishments for this week. Next week we plan to further work on our bridge to reduce the cost. We have also prepared some bridge specific questions to ask Mr. Bhatt during his visit next week. Currently, there are no issues that we face individually or as a team.

Figure 1: Group Bridge Design

After using the West Point Bridge Design program for a couple of weeks, we can point out the realistic and non-realistic features of the program. In real world, designing is an open-ended process in which one can alter their designs multiple times in order to achieve a better result. The real world also has specific conditions and restrictions, which is demonstrated by WPBD by limiting our span lengths and the limited variety of materials available. WPBD conducts standard load tests and calculates the compression and tension forces as specified by AASHTO, the standards which govern the design of highway bridges in US. These features allow WPBD to be considered realistic. However, there are a few things not considered in WPBD which would greatly be affected in real world.

The cost in WPBD doesn’t accurately reflect labor cost etc. which would offset the budget in real world. WPBD also does not consider fatigue- the tendency of a structural material to fail prematurely. WPBD allows and displays the deflection of the bridge and lets us compromise the bright strength with the cost. In real world, the deflection and bridge strength are a major criterion as we take the safety into account. While conducting the load test, WPBD moves the truck in one direction and does not have more than one vehicle on the bridge simultaneously. This allows us to have a functioning asymmetrical design. In real world, though, traffic would be moving in both the directions, and would have multiple vehicles travelling on the bridge. Along with the live load, real world bridges would also have to withstand rain, snow and other forces caused by external objects which are not considered in WPBD. All in all, WPBD is a good tool to gain basic knowledge about bridges, but we should consider the face that non-realistic features outweigh the realistic features in the program.

Week 2

During the second week, we were shown a PowerPoint presentation with a few different types of bridges that had truss designs in them. We also viewed video clips of two fatal bridge collapses and learned more about the bridges along with some vocabulary. We utilized the remaining time in familiarizing ourselves with the West Point Bridge Design software by designing a bridge. For the next week, our group will be evaluating each other 

individual bridge designs and combining different ideas to design the final bridge.

Major accomplishments from the second week include the installment of WPBD on my personal laptop as well as acquiring the basic knowledge of utilizing it to design our bridges. I learned some different features about the software during the process of designing my own bridge which include but are not limited to the different types of steel beams we can use, the thickness of each member, different viewing angles of the animation etc. There are not any issues that we face right now.

Some potential questions that I can ask Mr. Bhatt during his visit to our class include:

1. Would I be able to find a book or a collection of bridges that have failed to perform well? This can help us explore the specific faults that caused the failure and keep us from using a design like that for our bridge.
2. What would be a good resource that would provide us with visual data (pictures, blueprints etc.) on famous truss bridge designs?
3.  Is there a source that would let us input the basic information of our bridge design and help us calculate the force/ load on different parts of the bridge?

Week 1


During the first week of ENGR-103, most of the class time was taken to explain the course goals and objectives. In the remaining time we divided into groups of 3 people who will be working as a team for the bridge design module. We introduced ourselves to each other, exchanged contact information and filled out the group information sheet. In the coming week, we plan to conduct some research on different types of bridges so we can enhance our knowledge and incorporate those ideas in our own bridge design. For example we can see how an arc shape can be integrated with a truss design. Our major accomplishment from week 1 is the setup of our blog which is a major component for this course. There aren’t any major issues that we face at this point since it has only been one week and we haven’t gotten deep into the project components yet. The first week’s reading focuses on teamwork which is not only a part of this course, but almost all the engineering fields. With multiple people in a group, there may be a few problems that may arise in the future. For example, not everyone’s thoughts and opinions are always going to be the same when making a decision. In which case, we plan to give everyone a chance to explain their opinion and listen to them from their point of view, and then make our decision based on the facts presented. One of the other problems might come up when deciding on a group meeting time. Since everyone would have different schedules, and me being a commuter, it would be hard to decide on a time that is convenient for everyone. In that case we would have to compromise and work our way around the busy schedule.