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Bridges

8th Grade ScienceButler Middle School

Lowell, MA

Bob, Paul and Ms AdamsApril 24, 2012

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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 BridgesBeamCommon on Interstate

Highways

Suspension Can be quite long and high

Roadway hangs from cables

Can tolerate some movement

in high wind

ArchVery 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 BridgeBending, Compression and Tension

Load

Compression Forces

Tension Forces

Reaction Reaction

Green St. Bridge over Concord River, Lowell, Ma

Arch Bridge Forces

Load

Compression Forces

Reaction Reaction

Suspension Bridge Golden Gate, San Francisco, Ca.

Load

Tension Forces

Reaction 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