Week 9: Bridge Process

During this in class, my group and I sort of just recollected and stepped back to decide how we were going to move forward from here on out. First we tackled the problem we were having with the online Bridge Designer portion Assignment 3, and once that was worked out we started working on our new bridge design for the 36-inch span. We decided the best thing to do was to create a completely new design for this new task, because our previous bridge did not perform as well as we would have liked. Also from calculating the method of joints, and using the online bridge designer we learned that a taller bridge is actually sturdier. Of course, we know we need to take cost into mind while making our new design. In the next week we hope to branch off of the design we created in class today, and test it to find its weak spots. Then we will be able to come up with a plan on how to make those weak spots stronger for the competition next week.

            This course has taught me overall that designing a bridge is NOT as easy as it looks! So many things need to be taken into mind when not only designing a bridge but also building it. The way the gusset plates are positioned could in the end make the difference between weather a bridge fails at 5 pounds or 40 pounds. Cost we found to be a huge issue. When your designing a bridge, you not only ask yourself “how can we build this bridge to make it hold the most weight in the class” but also “how can we modify our design, to make it cost the least it possibly can”. All in all this course was a great learning experience in all things bridge related.

Kelsey McSorley 

A-3 Question 5 McSorley

We found that the bottom deck truss was what was causing many of the problems we were having with the online Bridge Designer. Because of this, we decided to modify our actual bridge design to make an online design that would work. We kept getting an error telling us that the members plus three needed to equal to twice the nodes, causing the design to be "statically indeterminate". Our new online design is:

                                                           Image 1

As you can see we had to remove the deck truss, but I think if we had the deck truss in this design, it would decrease the tension in the middle nodes and move it to the outside nodes.

A3 - Chelsea Moss

Method of Joints

Calculations for each joint member were obtained by using the Method of Joints structural analysis. A free body diagram was drawn to figure determinacy of the problem. Each individual joint member was composed in a series of calculations to solve for reaction and internal forces within the bridge when load is applied. These calculations help visualize tension and compression forces so that efficient alterations can be made.

The diagram in Bridge Designer must be scaled properly to that of its tangible prototype. When conducting the Method of Joints calculations by hand, its particular measurements are considered. Therefore, the same must be done in order to achieve corresponding accuracy. The results shown in Bridge Designer verify this common oversight because they were a multiple of our original values. Consequently, the results must also be scaled to correlate with its dimensional proportions.

Week 8: Truss Analysis

This past week in lab we discussed the process of bridge analysis. Through the guidance of online resources, we learned how to calculate the individual forces exerted on the joint members when experiencing a load. This method was called the “Method of Joints.” To do so, we drew a free body diagram to figure determinacy of the problem. From there, we used a series of calculations to obtain the reaction and internal forces stressed upon each joint member. Once the calculations were obtained, we compared are hand-done work to that of online program by creating a diagram of our design and entering our scaled dimensions and load applied to determine the same results. The online program provided us with results that were multiples of the values we had calculated.

The Method of Joints proved to be an accurate telling of which beams were under tension or compression; however, further structural analyses should be conducted and conditions considered to achieve absolute stability.  In this upcoming week, I plan to complete further analyses when designing the final bridge.

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.