Building an efficient bridge requires optimizing the strength to weight ratio while still adhering to size and safety specifications. To tackle this challenge, I built a 271g wooden bridge with a team in ENGS 33: Solid Mechanics that withstood 4.7 kilonewtons of force (equal to 1,056 pounds of force). We performed hand calculations of the forces exerted on members of a simplified truss, then designed an improved arched truss with a curved deck in SolidWorks. We tested this bridge extensively in FEA simulation to optimize the design before laser cutting the parts and assembling.
Assembly of the parts using generous amounts of wood glue and clamps.
Force testing the fully constructed bridge on an INSTRON machine.
After testing the bridge, we found that our actual load and deflection were better than predicted through SolidWorks FEA. The bridge failed as expected by buckling along the topmost edge of the truss. The arched design likely contributed to its improved strength. Its final strength to weight ratio was very efficient at 3.9 pounds of force per gram of weight.
