2.  Every bridge ever constructed had the same 4 stresses to overcome.  Tensile Stress- Forces that try to stretch material and pull it apart.  Compression- Forces that try to push or squeeze material together.  Shear Stress- Forces that try to make materials tear and slide by each other.  Torsion Stress- Forces that try to twist and bend material.

3.  Pier- A strong support that helps a bridge with stability.  Caisson- A Tube used for bridge foundations when built over water.  Bedrock- A strong foundation that support bridge piers.  Keystone- A critical part of an arch bridge that keeps it together.

4.  Beam Bridges ◦ Girder- Box-girder or I girder laid between two piers. ◦ Cantilever- Built so that middle beam is supported by two outside beams. ◦ Truss- Uses a series of triangular shapes to distribute weight across the beam to piers.

5.  Arch Bridges ◦ Abutment- Where the bridge meets the land, keeps the arch from pushing out and down ◦ Aqueduct- A man-made channel that carries water built by the Romans to shield the water from sun and contaminations.

6.  Suspension Bridges ◦ Suspension Bridge- A bridge deck that is supported by cables hung from towers ◦ Cable Stayed Bridge- Single towers are used to suspend the road surface.