Experiment: Comparing roof truss structures

Aim:  To determine which structure is best for roof trusses/bridge girders

Materials:  Poplar wood /ice cream sticks/grass straws, stikistuff/drawing pins/glue, tin of sand, 2 bricks, weighing scales

Method

Models of roof structures (a-d) and girder bridge structures (e and f)

1. Build models of roof trusses and bridge girder using ice cream sticks/grass straws or poplar wood
2. Support each structure on bricks at the two thrust points
3. Load each of at the point shown by the load arrow using the tin of sand
4. Find the load each structure can carry by weighing the sand in the tin at the moment the structure breaks
5. Repeat this for each structure
6. Ty to determine which beams are in compression ( the ones that collapse in inwards)
7. And which ones are in compression (the ones that collapse outwards

Observations and Results

This is one of the strongest roof truss structure types

• For house roof structure d holds the most load before collapsing.
• Structure c holds slightly less weight when compared to d followed by structure b which holds less weight
• Structure a holds the least weight before giving in
• Structure f holds more weight compared to structure e which is susceptible to shear forces

Conclusion

• Structures d and f hold the most weight

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