Truss Destruction
Students work within constraints to construct model trusses and then test them to failure as a way to evaluate the relative strength of different truss configurations and construction styles. Each student group uses Popsicle sticks and hot glue to build a different truss configuration from a provided diagram of truss styles. Within each group, each student builds two exact copies of the team's truss configuration using his/her own construction method, one of which is tested under shear conditions and the other tested under compression conditions. Results are compiled and reviewed as a class to analyze the strength of different types of shapes and construction methods under the two types of loads. Students make and review predictions, and normalize strengths. Teams give brief presentations to recap their decisions, results and analysis.
Trusses are tried and true designs for bridges.Copyright US Department of Labor http://www.osha.gov/doc/guidance.html
Structural engineers are involved in the design and engineering of many objects we encounter in our daily lives, from bridges to buildings. When designing a structure, engineers rely on the results of many empirical tests to predict the performance of their structures. In this activity, students engage in the engineering design process to determine a structure's maximum strength under two different load configurations, shear and compression forces. Students rely on known truss configurations, but are given the freedom to engineer their own construction methods, and then compare their relative performance.
After this activity, students should be able to:
- Describe the difference between shear and compression testing.
- Analyze data on configurations and construction methods and report which proved to be the strongest under two load conditions.
- Communicate how structural engineers use load-failure data to design structures.