WPBD

            At this point in the quarter, all of the students participating in out engineering 103 lab section involving bridge design have been using a specific application provided by the school for the creation of the designs and models.  This application also serves the useful purpose of helping us engineering students learn about judging the different effects and properties of the particular shapes and materials used in a respective design.  Last week we modeled and submitted our own designs, while during class we compared them with our classmates and each group submitted a new one that the students felt represented each group.  As for my teammates, we all agreed we liked the stability of triangles, however more time needs to be dedicated familiarizing ourselves with the different materials and their effects on the design and price, a skill we will all need to acquire.  At least we accomplished to learn about the different factors that apply when designing a bridge.

            To address the question at hand of weather the program currently used for designing a bridge is realistic or not there are more than one factor to the answer this question.  On the one hand, the program is exaggerated with many reactions of the bridge, which can often be considered unrealistic, however it makes sense why they would want the designers of the bridge to understand the risk a t cost and see exactly where they fall wrong with each design.  Additionally, no matter how much designing one does on a computer, it is most probable that nothing truly resembles the real world and its rules   The design matters, very much, nevertheless is not the, only component to a good code and experiment, or work environment for that matter.  Which may or may not affect how realistic this program is seen as, but that depends on the yes that are judging it and their own definition of realistic and unrealistic.

-  Ana M. Franco

West Point Bridge Design

Last week each student in the class submitted their own bridge design to our professor, James Mitchell, online via a survey. In class we compared the results of each bridge side-by-side. My bridge, coming in at close to $590,000, was one of the most expensive. The least expensive bridge had a cost of just below $250,000. I clearly wasn't going to be winning this first competition.

For the rest of that class period, each group was to analyze the bridges each member of the group had created. My group members and I decided that we would benefit the most by attempting to build a bridge entirely from scratch on West Point Bridge Design, keeping one goal in mind: have a cost below $250,000. After about 50 minutes had passed, the least expensive bridge we could design would cost about $440,000. I was happy with this, however, because in about a day I'd learned how to reduce the cost of a bridge by over $100,000.

My group and I decided we would play around on WPBD before our next class together, but our group's bridge had already been submitted and there was no way we could do anything to change our design's official status until the next class. I am very much looking forward to seeing the results of the competition between groups in class tomorrow. I'm sure our bridge is not the least expensive, but maybe it is the safest or the most durable. On another note, the group is not having any trouble working together. So far we haven't run into any issues that we cannot fix by simply looking in a book or asking a question to someone with a good understanding of bridges.

Going back to the WPBD program, I have noticed that some aspects of it are not very realistic, however, the program helps the used understand many important areas of civil engineering. As we discussed in class, when you test a bridge, the program exaggerates the displacement of the bridge's road surface so that the user can easily see how significant the changes are that they make to their bridge.

Without even realizing it, users of WPBD are learning how civil engineers use computers as tools to help them perfect their designs. This program calculates the stress on each member of the bridge and displays it in a chart within a fraction of a second after running the test mode for a bridge design. This saves time for the civil engineer and allows them to make more changes to their designs without having to go through the process of manually calculating all the forces acting on each member of each bridge design.

Personally, my favorite part of WPBD is that it calculates the cost of my bridge for me. Every time I change the size, material, or structure of a member, the cost automatically updates. This makes it easy to avoid heading in the wrong direction with a design and ends up saving alot of time. The program provides standard options for bridge materials and dimensions which helps users learn which materials are the best for designing bridges.

Overall, the program is unrealistic in the sense that it does not account for certain forces which act on bridges. Wind is something that can significantly affect a bridge in reality, but the program does not provide for such a force. All of the things that program does do accurately definitely help the user speed up the process of designing a bridge.

The Reality of West Point Bridge Design

West Point Bridge Designer is a great program to start designing bridges with.  It helps you to understand how to design structures, provides an idea of the engineering design process, how to improve the effectiveness of bridge designs, and provides a tool to help us figure out how structures work.  Although all of this is great, WPBD is not entirely realistic.  WPBD focuses more on the design process than the structural design of the bridge.  Although it will tell you if the design is stable for a specific computer coding, that does not mean it will work in real life situations. 

                In a real life situation, many different kinds of materials, connectors, and members are used.  West Point Bridge Design offers some variations, but not as many as engineers consider when designing a real bridge.  Engineers also have to consider roadways, weather conditions, the body of water the bridge is going over, and a three dimensional structure.  WPBD allows you to make some changes to the roadway, but not enough to get a real sense of the design.  Along with environmental concerns, bridges undergo a lot of fatigue and engineers must figure out what kind of material to use to make the bridge last as long as possible while still being efficient. WPBD does not consider this, making the user unaware of the efficiency of their bridge.  The user would also be unaware of how much weight their designed bridge could hold.  In actual bridge designing, many different forms of vehicular traffic have to be taken into account, along with the self-weight of the bridge and environmental conditions, such as snow or an earthquake.  West Point Bridge Design accounts for some failures that occur from the design, but not all that could occur on a real bridge.  Engineers must take these added failures into account, including deflections that occur from driving on the bridge or weather.  West Point Bridge Design fails to do this completely.

                Although West Point Bridge Design does not accurately represent a realistic bridge, it is a very good learning tool for students.  It focuses on the fundamentals of building and using trusses, and gives a good representation of how a bridge would act if weather, vehicular loading, and the river were not factors of the design. 

                In week 3 of lab we reviewed the results of our A1 designs and then each team developed an improved design in class. Our team’s design was improved from any of our individual designs, but did not come close to competing to the most cost efficient. Unfortunately, the lowest we could make it in the time allowed was around $41,000.  We were happy with our design but I personally wished we had more time to work on it to see how cheap we could make it. 

                For this week in lab, I hope to gain a better understanding of how a bridge holds weight as we will be using Knex for the first time.  I know we will have to document how much weight it holds and I would really like to be on my game the first time around.  I hope to accomplish an efficient design that my team will like.

A1 - FRANCO

I have designed my first bridge following the use of triangles.  The reason is, that with the advantage of their strength and sustainability if done properly, less material would be necessary for the needed amount of strength, which would also make it a more affordable bridge.

My bridge began using a lot more material and smaller similar shapes of triangles.  As I modified the bridge and its angles, I was able to gradually remove material used and make it more economic.

Current bridge cost:  $354,192.01
Estimated bridge cost (future improvements included):  $425,000.00

During the making of this design I learned that not only does the length of a rod matter, but also do the angles and it can significantly affect the way the force sustained is distributed.

Research Questions

During class in week 3, Mr. Jay Bhatt, Drexel University's research librarian, will be visiting to help students with strategies for research. In week 2, Mr. Bhatt spoke to the entire Engineering 103 student body about using the library's website as a main research tool. He showed us where to find different databases to search all sorts of subjects and he helped us to understand which resources to use to find certain types of information.

After completing my first bridge design for Engineering 103 using the West Point Bridge Designer computer program, I have begun to notice patterns that fail and patterns that are successful for bridge truss designs. I have specifically noticed that on alot of designs I came up with, the top of my truss was weaker than the bottom. I understand that this is because of the way weight is dispersed across the bridge, but I would like to learn more about strong triangular designs commonly used in trusses and what it is about these designs thats makes them so popular.

I am hoping that Mr. Bhatt will be able to help me find resources to answer the following questions:

1. Does the design of a truss above/below the road surface of a bridge affect the bridge's potential strength? If so, does placing a truss above the roach surface of the bridge make the bridge stronger or weaker?
2. Is it better for a truss to be made of small triangles of equal size or large triangles of varying sizes?
3. Is there a certain way to go about designing a truss? Are there any base-designs or patterns to follow other than using all triangles?

Research Questions

Mr. Bhatt was introduced to the engineering student body during week two of the quarter.  He spent an hour informing us of all the great resources there are out there on the web for us to use, especially when we need information regarding engineering.  These seem like very helpful places to go when researching for projects.  I am sure I will use at least one of the resources he discussed when researching about bridges.  

However, I still have a few questions as to how to go about my research.  One thing I would definitely like to know is where exactly to start researching them online.  Are there better websites than others?  How do I know what websites will be the easiest to understand?  Is there somewhere I can go to learn about the general formation of truss bridges?  For someone who knows absolutely nothing about bridges, what’s a good beginner website to start my research at?  These are just a few questions that would be really helpful.  My biggest concern is that I will only find websites that are hard to understand and that will go into very detailed explanations.  First, I need to learn and know the basics about bridges before I will be ready to conquer the harder descriptions. 

On a more detailed note, I would also like specific questions about bridges answered.  I noticed that there are two major ways to design a bridge on WPBD.  What are the pros and cons of building the truss above/below the bridge?  I also would like to know how to make the strongest bridge.  I know that triangles are a must, but should they be big or small? Equilateral or all different shapes? I am hoping that Mr. Bhatt can answer these questions and more in Wednesday’s lab.

A1-O'CALLAGHAN

Goals for my bridge design:

• Truss design consist mostly of triangles
• Have a general square shape for the bridge
• Have a two lane truss bridge that did not include pillars 
•  Keep the cost down 
•  Use as few members as possible and still be considered steady

                                                            View of bridge in building mode









                                                                   Image of truck in center of bridge


                                                   Load Test Results

My design originally changed from when I started the design process.  I am still getting used to WPBD the program, so a lot of things I did were experimental.  I started out thinking that a lot of small triangles would be best, but I soon realized that it was also more expensive.  I basically tried to come up with the cheapest bridge I could that supported the truck.  I learned that members couldn’t be too thin and I had to find a happy medium in the length of each member.  Overall, I am happy with the design since it is my first time designing a bridge. 

The cost estimate turned out to be $438,282.34.  I played around with a few other designs and out of the three bridges I saved, this one was the cheapest.  I hope to eventually decrease this to under $400,000 but I feel this will take practice and patience.  

Overall, I learned how to use WPBD and how to build a beginner bridge.  I found the load test results to be very useful and the truck simulator to really help me understand why my bridge was failing at certain points.  In the future I hope to build upon my knowledge so I can improve my bridge building skills and create more efficient and stronger designs.