INFLUENCE OF THE DESIGN ON THE STRENGTH OF A BRIDGE PURPOSE The purpose of this project is to compare three different designs spanning over a short constant distance. The materials for all the bridges will be constant as well. I will be comparing the truss, cable stayed and the beam bridge to determine which type of design will hold the heaviest load.
HYPOTHESIS My hypothesis is that the truss bridge would be much stronger than the other two bridges. My research indicated that truss bridges can support very heavy loads, most bridges that railroads are built on are truss bridges and the beam bridges are fine if you are carrying light loads over short distances.
EXPERIMENT DESIGN The constant in this study will be the distance the bridges will span, the height, the materials used in the construction, and the way the bridges will be tested. The manipulated variable will be the design of the bridges.
The resulting variable will be how much mass each bridge design will support. The resulting variable will be measured in pounds.
MATERIALS Balsa Wood strips 1/4 inch wide Pine center beam for cable stayed bridge 1/10 inch bass wood for bridge road base Fishing line - 50 lb. Test, .029 diameter Bottle of glue Weights used to test strength of the bridges 2, 2ÃÂ½, 3, 4, 5 and 10 pounds Weight scale Additional weights were improvised using heavy books PROCEDURES 1) Gathered materials 2) Built the three bridges 149/16 inches long and 4ÃÂ½ inches wide 3) Build two end bases to hold the side of the bridges 4) Take pictures of the beam, truss, cable-stayed bridges 5) Begin testing the cable-stayed bridge first 6) Add weights to the cable-stayed bridge 7) Take pictures of cable-stayed bridge 8) Add more weights to the cable-stayed bridge,