Presentation on theme: "A Brief Overview of Bridges Preparation for Lab Grade 7 Science Ms. Willis."— Presentation transcript:
A Brief Overview of Bridges Preparation for Lab Grade 7 Science Ms. Willis
Learning Goals /Success Criteria I can describe different bridge types. I can identify geometric shapes used in bridge design. I will understand my expectations for the science lab in building our a model bridge.
Bridges Bridges provide important links between places. They enable us to get to resources, conduct commerce, travel and visit other people. The design of bridges is important to the transportation networks we depend on.
Types of Bridges There are many kinds of bridges, but generally they can be classified into 4 main groups: Beam bridge (includes truss bridges) Arch bridge Suspension bridge Cable-stayed bridge
Arch Bridges The Arch bridge is the shape of a curved arch with abutments at each end. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. This type of bridge was often used by the Romans who built structures out of stone.
Arch Bridges This is a Roman Aqueduct in France. It was difficult to span wide distances without using several arches with supports. The piers to support these arches can restrict water flow which can be hazardous. These bridges can date as far back as the 1300s!
Arch Bridges This bridge is located in Southern California. A modern arch bridge.....
Arch Bridges Note: A voussoir (pronounced /vu ˈ sw ɑ r/) is a wedge-shaped element, typically a stone, used in building an arch or vault.
Suspension Bridge A suspension bridge is a type of bridge in which the deck (the load-bearing portion) is hung below suspension cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 19th century. These bridges can support tremendous weight and span a wide distance.
Suspension Bridges Mackinaw Bridge in Michigan Total Length: 8 038m Length of main span: 1 158m Height: 168m Longest suspension bridge in Western Hemisphere.
Cable-Stayed Bridges A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge deck. There are two major classes of cable-stayed bridges: harp and fan. Harp bridge in Dublin, Ireland Fan bridge in Washington, USA
Cable-Stayed Bridges Cable-stayed bridges differ from their suspension predecessors in that they don't require anchorages, nor do they need two towers. Instead, the cables run from the roadway up to a single tower that alone bears the weight. The tower of a cable-stayed bridge is responsible for absorbing and dealing with compressional forces.
Beam Bridges The beam ends rest on two or more piers or columns. A simple beam bridge is made of horizontal rigid beams.
Beam Bridges The size and the material of the beams determine the amount of force the bridge can withstand.
Beam Bridges Truss bridges distribute the weight differently and are often used for heavy car and railroad traffic. Truss bridges are a type of beam bridge.
Beam Bridges There are several different styles of Truss Bridges:
Beam Bridges Truss bridges distribute the weight making the beam bridge much stronger with less material.
Let’s Take a Look.... A closer look at how bridges are built: https://www.youtube.com/watch?v=hwzXXXUAKVU For interest: 25 Scariest Bridges! https://www.youtube.com/watch?v=_OIHRh6dto8
Review! Quiz to check your knowledge about bridges: http://science.howstuffworks.com/engineering/structural /bridge-quiz.htm http://science.howstuffworks.com/engineering/structural /bridge-quiz.htm Decide the best place to put each type of bridge: http://www.pbs.org/wgbh/nova/tech/build-bridge- p1.html http://www.pbs.org/wgbh/nova/tech/build-bridge- p1.html
Your Assignment! Now it’s your turn! In groups of 2 or 3, you will build your own bridge. Follow the steps on your assignment sheet!
Review of Unit A review of our unit, Structures: https://www.youtube.com/watch?v=u2iPj4Cjajk (Bill Nye) https://www.youtube.com/watch?v=u2iPj4Cjajk