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Bridges. 8 th Grade Industrial Technology. Instructional Objective. Students will be able to identify the three types of bridges. Span the shortest distance (200 feet) Least expensive and most common. Beam and Span. A beam bridge may be as simple as a log across an open span.
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Bridges 8th Grade Industrial Technology
Instructional Objective • Students will be able to identify the three types of bridges
Span the shortest distance (200 feet) Least expensive and most common Beam and Span
The Beam BridgeA beam bridge is basically a rigid horizontal structure that is resting on two piers, one at each end. The weight of the bridge and any traffic on it is directly supported by the piers. The weight is traveling directly downward.
Simple Beam Bridge The pier at each end may also be called an abutment
Beam Bridges Modern beam bridges are good for short spans. CR North
Beam Bridges Scudders Falls Bridge For longer spans, a series of beam bridges may be put together. This is called a continuous span bridge.
Beam Bridge (Truss Design) Another type of beam bridge is known as the truss bridge. The truss bridge is made up of a framework consisting of straight bars (usually steel) that are arranged in triangular shapes.
Truss Bridges Truss bridges are lighter weight and can have a longer span than solid beam bridges. This is because they distribute weight evenly.
Truss Bridge Dingman’s Ferry bridge crosses the Delaware River at the town of Dingman’s Ferry
The Washington Crossing Bridge is an example of a continuous span truss bridge because it has more than one section.
The Calhoun Street Bridge from Morrisville to Trenton is also a continuous span truss bridge.
Arch Bridges Arch over the roadway Arch under the roadway
Arch Bridges The arch bridge...has great natural strength. Thousands of years ago, Romans built arches out of stone. Today, most arch bridges are made of steel or concrete, and they can span up to 800 feet.
They can be made of solid material such as stone or concrete.
Arch bridges can be strong enough to carry trains, such as this one near Yardley.
Used for spanning long distances up to 7000 feet Most expensive Suspension
Roadway Cables Main Cable Suspension bridges use large cables to suspend the roadway from above. Here is a view looking down from the top cable of the Golden Gate Bridge.
Suspension Bridges The main cables on the Golden Gate are about 3 feet in diameter
The Golden Gate Bridge in San Francisco is one of the most photographed bridges in the US.
The Golden Gate also has a section of trusses to add strength and stability.
The Cable Stay bridge is a suspension bridge without a main cable
Large bridges may utilize more than one style Beam Suspension
Bridges Video Clip • View the short video discussing the various types of bridges