A bridge must carry a load across a gap to supports. A beam does this partly by bending. A triangular frame can carry squeezing forces in some members and pulling forces in others. With a centred load on this symmetric model, the supports share the upward force equally. Pulling is called tension; squeezing is called compression.
Engineering and scientific investigation · Discover & try
How can a bridge pass a load to its supports?
Reading level 1 of 5 · EarlyChange
Word help
Tension
A pulling force along a member.
Compression
A squeezing force along a member.
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See how it works
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Ideal symmetric beam/truss force paths with a central load. Deformation is exaggerated and connections are simplified.
What to look for
- The beam bends under its central load; both supports share the load.
- The upper members are squeezed while the lower tie is pulled.
- Each equal support reaction grows from one to two model force units.
Explain what you noticed
A cable in a different structure is pulled at both ends. What name describes that internal action?
Keep this idea: Loads must reach supports, but different structural forms carry internal forces differently.
Follow the sources
- University of Colorado Boulder / TeachEngineering — Analysis of Forces in a Truss Bridge
- University of Colorado Boulder / TeachEngineering — Building Our Bridge to Fun
Source material checked 2026-10-29. Explanations and activities by Nepedia. Source links do not imply endorsement.
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