7th Grade Bridge Unit Vocabulary

Learning Targets:

  • I can explain the advantages and disadvantages of constructing a beam, arch or a suspension Bridge.
  • I can identify the different types of beams used to make a structure stronger.

Essential Question: What is compression? What is tension?

Bridge Unit Vocabulary Part 1: Please study all vocabulary words, images & definitions.

The following words and definitions were discussed in class and should be written in your notebook. Create vocabulary cards to help you study.

  • Bridge – a structure carrying a road, path, railroad, or canal across a river, ravine, road, railroad, or other obstacle. Bridges gives a way to get from one place to another.
  • Compression – a force that pulls materials together.
  • Tension – a force that pulls materials apart.

  • Stability – A structures ability to maintain or regain a stable position. Structures do move.
  • Center of gravity – The point where the mass of an object is equally distributed in all directions.
  • I beam – a level structure usually made of metal that supports a load. The beam shape resembles an I.
  • Corrugation – bending the material, folded material.
  • Rebar – metal bars that are bumpy, used to reinforce a structure, such as a large walls. Rebar can be placed between the cement that might be used when building a wall or sidewalk.
  • Cantilever – a beam that is only supported on one side.

  • Tensile strength of materials. This is the maximum force that can be applied to a material without pulling it apart.
  • Span – the length of a single bridge segment, between two vertical supports called piers.
  • Gravity – The force that pulls everything on the earth’s surface towards its center.
  • Buckle – bend and give way under pressure or strain.
  • Displacement – movement of a force from a weaker area to a stronger area.
  • Dissipate – to break up, to cause to spread thin or scatter

Supporting a beam:

  • Tie – a support on top of a beam to prevent tension.
  • Gusset – a support placed in a tie position, on top of the beam but it’s a solid piece of material shaped like a triangle. A gusset prevents tension and compression.
  • Strut – a supports beneath the beam, this prevents compression.

Larger Construction:

Three (3) basic types of bridges:

  1. Beam bridge – simple but weaker of the three types of bridges.
  2. Arched – stronger than a beam bridge.
  3. Suspension Bridge – The strongest design of the three bridges. The stronger the bridge the more distance it can cover in a single span

.

  • The Truss: a network of beams (each one of the lines in the diagram represents a beam). This is in a triangular formation. The triangle structure is the strongest structure there is in a building.
  • The Arch – a solid piece with a ½ circle , looks like a moon. This spreads out the mass or the load over the arch.

  • The Dome – a solid shape, it spreads the mass or load in equal directions all the way around.

Advantages of Bridge Designs:

Garabit Bridge – The Garabit Viaduct (Viaduc de Garabit) is a railway arch bridge spanning the River Truyère in the mountainous Massif Central region of France.

http://www.bridgesofdublin.ie/bridge-building/famous-bridges/garabit-viaduct-1884

Akashi Strait Bridge, also called Akashi Kaikyo Bridge or Pearl Bridge, suspension bridge across the Akashi Strait (Akashi-kaikyo) in west-central Japan. It was the world’s longest suspension bridge when it opened on April 5, 1998.

https://www.britannica.com/topic/Akashi-Strait-Bridge

China Opens the World’s Longest Bridge Over Water, Toppling American Record-Holder

https://www.popsci.com/technology/article/2011-07/china-opens-worlds-longest-sea-bridge-toppling-american-record-holder

New York 21st Century Development

https://www.governor.ny.gov/news/governor-cuomo-announces-transformational-plan-reimagine-new-york-s-bridges-and-tunnels-21st

Understanding Bridges: Types of Bridges – Brainpop

Brainpop.com (see teacher for code). https://www.brainpop.com/technology/scienceandindustry/bridges/

In the movie, Tim explains the three main kinds of bridges, but engineers have tweaked those basic designs in dozens of ways. These are just a few of them.

Brunel Truss: A hybrid arch-suspension bridge, the one-of-a-kind Royal Albert Bridge (A) is suspended by cables from an arched metal tube. Trusses crisscrossing below the arch give added support.

Stressed Ribbon: Would you drive a car over something called a stressed ribbon bridge (B)? A variation on the suspension bridge, the ribbon arcs up and down between supports. Despite the name, they’re actually stiffer and more stable than traditional suspension bridges.

Cantilever: A cantilever bridge (C) is basically a beam design, but with one important difference: the beams are supported on only one end, just like a diving board. Most of these bridges have two cantilevers—one on each side—that meet in the center.

Cable-Stayed: A descendant of the suspension bridge, the cable-stayed bridge supports its roadway through cables attached directly to the support piers, or pylons. This results in a look that is rather cool. Cooler still is the cantilever spar cable-stayed bridge (D), a cross between the cantilever and cable-stayed bridge that was first designed by the Spanish architect Santiago Calatrava. Welcome to the future of bridge design.

Real World Connections:

A tall suspension bridge usually provides enough clearance for big ships to pass underneath—but they are expensive. So engineers have developed a slew of smaller, moving bridges instead!

Drawbridge: This classic design, featuring one hinged end that can be hoisted with ropes or chains, has protected castles for hundreds of years.

Bascule: Often called drawbridges, bascules like the Tower Bridge in London are the most common movable bridges. Counterweights hoist the split roadway upward.

Lift bridge: Using counterweights, lift bridges vertically lift a section of the roadway on towers.

Swing bridge: The central section of a swing bridge uses motors to rotate 90 degrees when boats have to get by.

Submersible bridge: The opposite of a lift bridge, submersible bridges lower a section of the roadway underwater.

Curling bridge: There’s only one curling bridge in the world: London’s Rolling Bridge (pictured). It consists of eight triangular segments that can curl up into a circle, thanks to hydraulic pistons.

Disadvantages of Bridge Designs: Infrastructural problems with new Bay Bridge in San Francisco, CA

  1. http://www.nytimes.com/2011/06/26/business/global/26bridge.html
  2. http://www.sfgate.com/bayarea/article/Tests-of-Bay-Bridge-rods-find-more-widespread-6135790.php
  3. https://www.wired.com/2015/06/mystery-brand-new-bay-bridges-corroded-steel/
  4. https://www.docsteach.org/shared-documents/favorite/NjYwNQ==

History of Bridges:

Links to websites about the history and mechanics of bridges

Videos:

http://www.pbs.org/video/curious-crew-bridges-ep-207/

Bridge Disasters:

Modern Marvel