A3- Mercado

4) The bridge in bridge designer must be scaled properly in order for the forces to be correct. For example if the bridge is 2 feet then maybe each square should be 2 inches. Scaling keeps everything in the same proportions which allows for the forces to interact in a similar way except on a smaller scale. 

6) This information about the forces experienced by the beams could be useful in bridge construction. This shows what beams are experiencing the least amount of forces and the most amount of force. Once it is determined what beams are under the most force then additions and changes can be made to disperse the forces.

* I tried my best with number 5 it didn't function as it should have 

A3- McSorley

1.)

                                                           Image 1

2.)

                                                           Image 2

3.) 

                                                            Image 3

4.) When we were doing the Method of joints hand analysis, we realized that the numbers we were finding were not identical to the numbers given to us by the online Bridge Designer. This worried us, but then we also realized that there were no units given to us by the online bridge designer and this cause us to think that in order to get those numbers it would just come down to scaling the numbers we calculated. The numbers, we found, were the same in the end but just differed by a common multiple and only needed to be scaled to be identical.

5.) 

                                                              Image 4

6.) Through this analysis I learned that when the angle is decreased, the force also decreases. This would cause me to want to build a bridge with smaller angles to decrees the force on each joint. By doing this I would improve my bridge design, and ultimately cause it to hold more weight. 

Week 8: Bridge Analysis

This past week in lab we learned about bridge analysis. Using online tools professor Mitchell provided on the blog and the help of our TA’s we learned how to calculate the forces the beams experienced when they experienced a load. This also showed us which beams are under compression and tension.  After doing the calculations by hand we drew a diagram if the sample bridge in an online program which calculated the forces manually.

            While knowing how much force the different parts of the bridge is under is useful, I think further analysis would be conducted for a real bridge. There simply is not enough data about the gussets and all the members. These calculations did not include the top and bottom members, while they may not have a big of effect on the bridge ass the side members it is still important to understand what they are doing. When making a real bridge any designer would test and calculate everything possible before allowing something so massive and important to be created. These calculations simply, leave too many variables out like consistent weight and the weather, both of which would have a significant effect on the bridge. In order for a bridge to be safe it is important to calculate how much weight it will take for the bridge to break. It is also important to know where the weakest point is in the bridge. Additionally, the designer would also have to calculate how consistent weight would affect the bridge over a long span of time. These calculations are vital to the bridges safety and feasibility and cannot be omitted. 

Week 8: Analysis Process

During this past week in engineering lab, my group and I worked a lot with numbers and calculating stress and compression of each joint and chord using trigonometry and a method called “method of joints”. For this, we first did our calculations by hand using a lot of physics and math to find the tension forces at each gusset plate. We then entered the dimensions and weight applied given to us into an online system created to calculate all of our hard work in the click of a button. Although the numbers we got from the online system didn’t match our numbers identically, we soon found out that they were simply multiples of the numbers we calculated. This coming week my group will create a new bridge that can span 3 feet, with the ideas that we have learned from our previous bridge.

            I think that this method of joints would be sufficient for calculating for a real bridge. In the real world the bridges we build have to be tested somehow, and a lot of the times, hand calculations would need to be done for them. I would like to further analyze maybe the different ways that this tension and stress can be relived, and how the design of the bridge can affect the forces acting on the bridge.

Kelsey McSorley

Week 7: Bridge Results and Analysis

        This past week in lab we tested our first truss prototype.  Melissa and I had toyed with the bridge design for some time before deciding on a simple design that consisted of one through truss with X’s in elevation and horizontal members in plan view. We felt that, although rough, we would see how the bridge performed to determine our next steps in design. Our initial plan was to focus on keeping the cost low, however we found that the weight supported did not exceed expectations as we hoped. Therefore, last minute alterations were made. Right before testing, we added a deck truss that followed our gusset pattern and included X’s on the outer plates, to prevent the bridge from failing from middle compression. The reason for this addition, from conclusion of trial and error, was that the weight needed to be dispersed to the outer edges. Although our theory succeeded in testing, our results were not impressive. Our final bridge cost $320,000 and supported 19 pounds.  Ultimately, our bridge failed at an outer gusset point, which was disappointing because much of our design was contingent upon the success of our gussets.

        

        For this week, our team needs to analyze our bridge designs through testing with thorough tension and compression measurements in order to modify and refine our final product. WPBD was a great tool because it provided us with those calculations, which allowed us to make modifications that affected both cost and strength efficiency. 

Chelsea Moss

Video of Bridge Testing: Week 6

Week 7: Bridge Results

This past week in lab we got to test the 2 feet bridges we built. Our bridge had a fairly simple design, following a concept I learned from the WPBD; Simple is better. It was a basic X truss across the sides that included an under truss. The idea behind the under truss was that It would help disperse the weight to the outside members. The under truss worked exactly as I expected. Our bridge broke right where the under truss ended. Our bridge only held 20 lbs. I was disappointed with our bridges performance but I was proud that it did not cost an extraneous amount, only $320,000. Another thing I noticed was that many of the bridges experienced the same failures. The Knex gussets are the weakest point on the bridge and through much testing I noticed that the arrangement of the gussets on the bridge mattered and could affect the failure point by several pounds. All the gussets alternated sides starting from the center covering the weaker point

I truly liked our final design but I knew deep down that it just wasn’t going to hold a lot of weight. I spent many hours testing a building bridges but it was hard to do without knowing where the compression and tension forces were and their magnitude. When working with WPBD one could look at the numbers given in the tension and compression columns and deduce where changes could be made to make the bridge strong and where beams were not being utilized at all.  This information can easily be found using trig. I know a main factor in tension and compression calculations are the angle in the triangles. So I would assume in the calculations the angles would be essential. Other than that I am not completely sure and can’t wait to learn Wednesday!

Melissa Mercado