Impact of Bridges: POLITICAL- relating to gov., link countries together ECONOMIC- make possible the transportation of goods and the provision of services.

BRIDGE BUILDING

Impact of Bridges:POLITICAL- relating to gov. ,

link countries togetherECONOMIC- make possible the transportation of goods and the provision of services

ENVIRONMENTAL- effect on fish and other water animals

CULTURAL- skills and arts developed during a certain period

SOCIAL-communities can travel

SUBSTRUCTURE OF BRIDGES

ABUTMENTS- support at the ends of a bridge

usually made of concrete

PIERS- vertical structural supports placed between abutments in longer bridges.

Piers are positioned to keep the longer bridge from sagging.

Made of wood, metal or

concrete.

Arch Bridge

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TYPES OF BRIDGE SUPERSTRUCTURES

Beam bridge- piers support beams that support spans of reinforced concrete slabs.

This is most common and least expensive.

ARCH BRIDGEThe load of the bridge is transferred along the arch to the abutments or piers at the end of the arch.

Arch Bridge

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SUSPENSION BRIDGEThese have two tall towers that support main cables that run the entire length of the bridge.

These bridges are used to span long distances.

Suspension Bridge

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Brooklyn Bridge Suspension Bridge in New York. The engineer who began the bridge died in a

bridge related accident. His son continued to build the bridge It took 14 years and 30 lives. The workers were afraid to tie the cables.

The engineers made pulleys and attached the cables themselves.

Golden Gate BridgeThe Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean.

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TRUSS A truss is a triangular

framework. It can be used above or

below the roadway to support the bridge.

Used in other types of bridges

Truss Bridge

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CANTILEVER BRIDGE

These beams extend from each end of the bridge.

Cantilever Bridge

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MOVABLE BRIDGEThese bridges are designed so that a portion of he roadway can be moved to allow large water vessels to pass underneath.

Moveable Bridge

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Tacoma Narrows BridgeWashingtonBuilt in 1940 Collapsed 4 months after being builtCalled the Galloping GertieWinds of 40 mph swayed the bridge

enough to collapse it.

Tacoma Bridge Informationhttp://www.enm.bris.ac.uk/research/

nonlinear/tacoma/tacoma.html

BALSA WOOD BRIDGE

PROJECTGoogle images

The Goal:

To build a bridge with the design that produces the largest strength-to-weight ratio during the destructive test

Bridge Efficiency = mass held by bridge/

mass of bridge

The bridge shall be an open frame structure designed to allow a 3 inch test block to pass parallel to the base.

The bridge must be free-standing and designed to span a distance of 10 inches.

The bridge must rest on a flat surface without the aid of external fasteners or bracing.

The bridge must be a minimum of 12 inches in length and the roadbed must be open throughout the entire length and must have a minimum overhead clearance of 3 inches.

The bridge shall be designed to accept a dead weight from the load platform. The load will be applied through the bottom of the bridge and will be guided from a 1/4” diameter rod passing through the center of the bridge.

To facilitate the insertion of the rod, the bridge must have a 1/2” diameter vertical opening through its center. The load platform is designed such that the load is approximately centered on the bridge.

The bridge must be wholly constructed from the furnished balsa wood and glue.

Other materials, such as straight pins, binder clips, tape, etc., may be used as aids for construction, but shall be removed from the bridge prior to submittal for testing.

The wood sticks may be cut and shaped at the discretion of the team. Single components may be combined to build-up members for use in final assembly.

No single piece of wood may have other pieces of wood laminated to more than two of its four faces.

Do not paint or stain the bridge. Do not impregnate the bridge with

glue. Glue must be confined to the points of contact between two pieces of wood.

MATERIALS

Balsa Wood 6 sticks ( 1/4 x 1/4 x 36 inch)

Super Glue 1 bottle

(use sparingly…it is heavy) Hobby Knife (optional) Super Glue remover Sandpaper

Project Overview• Balsa wood and glue construction• 2” width, 12” length, 10” span

(minimum)• Accept a dead weight applied

through the roadbed• Free Standing• 1/2” vertical opening

Web Design Support Check out the Building Big web site at:

http://www.buildingbig.com

Design your own bridge at:

http://jhu.edu/virtlab/bridge/bridge.html

http://jhu.edu/virtlab/bridge/truss.html

http://www.pbs.org/wgbh/buidingbig/lab/forces.html

http://www.pbslearningmedia.org/resource/lsps07.sci.phys.maf.dstruss/design-squad-truss-bridge/