Great Groton Gorge Bridge
By Sophie Scanlan and Nataniah Cagan
Forces Acting Upon Bridges
Cantilever
Compression:
- 2 sides act with each other pushing together but still balancing
Tension
- 2 sides act against each other
- Pulling away but balancing at the same time
Torsion
- Twisting force
- Dont want to have it in a bridge or it will collapse
Shear
- 2 opposing forces acting on the same point
- Occurs horizontally
- More or less an arch bridge that relies on diagonal bracing
- Only supported on one end
- Up to 1800 ft long
- Typically meet in the middle
Arch
- Use arches for support - arches always go under the bridge, not over
- Has supports at both ends
- 1+ hinges (depends on load and stress forces)
- Has supports on either end
- Up to 1741 meters in length
- made of steel or concrete
Our Choice
Truss Bridge
Suspension
- Stretches well across short distances
- Does not require downward vertical beams, which would not work for such a deep crevice
- Can be built well with the materials provided
- A beam bridge would snap in the middle and eventually bend into a v shape; the cover above the truss and triangle system beneath it prevents this from happening
- Span up to 2,000 - 7,000 ft across
- Most have a truss system beneath the road
- Suspension cables anchored at either end - load that the bridge supports is transferred from cables to towers
- Span long distances
- Resist earthquakes
- Uses less materials, costs less to make
Beam and Truss
- Beam
- Good for short distances, should not span more than 250 ft across
- Can be inclined or v-shaped as well as just straight across
- One beam supported on both ends by piers
- Truss
- Assembly of triangles made from straight bars
- Diagonal posts supported by straight post in the middle