- 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.
Three (3) basic types of bridges:
- Beam bridge – simple but weaker of the three types of bridges.
- Arched – stronger than a beam bridge.
- 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.
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.
China Opens the World’s Longest Bridge Over Water, Toppling American Record-Holder
New York 21st Century Development
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
History of Bridges:
Links to websites about the history and mechanics of bridges
- Brooklyn Bridge: 1883: http://www.history.com/topics/brooklyn-bridge