1 Bridges 8 th Grade Science Butler Middle School Lowell, MA Bob, Paul and Ms Adams April 24, 2012

2 Definition of a Bridge A structure spanning and providing passage over a gap or barrier, such as a river, road, railway or some other obstacle.

Basic Types of Bridges Beam Common on Interstate Highways Suspension Can be quite long and high Roadway hangs from cables Can tolerate some movement in high wind Arch Very Strong

Bridge Forces Compress Tension Bend Torsion Shear (squeeze) (stretch) (twisting) (cutting)

What kind of Forces? Tension, Pulling Apart Compression, Squeeze

Bending, Tension, Compression Tension Compression

Forces that can damage a Bridge Torsion - Twisting Bending - Pushes two ends of an object in same direction

Shearing Forces can also damage a Bridge Shear - Pushes in opposite directions within the material

3 Spans across Merrimack River, Lowell, MA

Forces in a Beam Bridge Bending, Compression and Tension Load Compression Forces Tension Forces Reaction

Green St. Bridge over Concord River, Lowell, Ma

Arch Bridge Forces Load Compression Forces Reaction

Suspension Bridge Golden Gate, San Francisco, Ca. Load Tension Forces Reaction

Newport, RI

Tyngsborough, Ma. Merrimack River

Bridge Street Bridge is a Truss Bridge

Bridge Street Bridge, Lowell, Ma Which geometric shape is most noticeable and why?

Triangle vs Rectangle Rigid Flexible (can change its shape)

University Ave Bridge, Lowell Ma Summer April 9, 2009

Paper Bridge Challenge Make a Bridge using 4 sheets of paper and a little tape