A1-Almendariz

A1-Almendariz

            In the second class we were assigned that each member of the group should design their own bridge.  The main objective of the assignment was to design a “safe” bridge that would have the best strength to cost ratio.  The bridge had some standard constraints and rules that they must obey: All bridges should be running through a “24” meter canyon.   Bridges should have a clear span meaning that they should not have any intermediate support.  Also they should not use any cable anchorages and use standard abutments.  They should be set to have a medium strength concrete (0.23 meters thick) two-lane roadway.  Finally through evaluation they should be able to support a standard load truck of 225kN.

            My bridge went through a series a changes to be able to reach what I think is a successful design.  Each change was made basically after testing the bridge watching for weak points and improving them.  I decided to initialize my design by using through Truss-Warren template.  I decided to use this template because I saw it as the strongest of all templates because I think that triangles are really successful in distributing the weight.  I decided to run the test by just using the template too see what were the main weak points that needed to be improved.  For this template the main weak points that I found was in the whole upper surface of the bridge.  The bridge would collapse completely, and the truck would not be able to even get on the bridge.  It is for this reason that I decided to add a similar second floor using the same idea of triangles as the original template.  After rerunning the test, there was a lot of improvement in the resistance of the bridge.  In difference from the first time, now truck would be able to run until the half of the bridge.  There was only three week points found that needed improvement.  There were two in each side of the second floor and one in the middle.  To be able to solve these weaknesses I decided to divide each section into two.  This would first shorten the size of each member and form two triangles.  With the changes made, the bridge was once more tested and its results were good.  The design did now have any single weak point, it was able to support the whole weight of the truck all the way through, and it didn’t bend significantly.  The final cost of the bridge design was $426, 912.12.  I think that with more time, the bridge design could be worked and improved to reduce its cost while keeping its strength.  From this design I was able to learn that triangle structures are really efficient in bridges and long members will have a lower strength.  The first image is from the final design in 2D from the "Drawing board view".  The second image when the bridge was been tested and the truck was right in the middle of it.  The last three images are from the "load test results".