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