1. Types of Structures  Residential - Structures in which people live.  Ex. Single family houses, condominiums, and apartment complexes.  Industrial - Structures used for manufacturing.  Ex. Automobile plants, computer chip manufacturers and power plants.

2. Types of Structures  Commercial - Structures built for business.  Ex. Supermarkets, shopping malls, restaurants, and office buildings.  Public Works - Structures intended for public use or benefit.  Ex. - Highways, bridges, tunnels, airports, hospitals, schools and parks.

3. Terminology zBeam – A horizontal structural member that is supported at two or more points. zColumn, post or pier– a vertical structural member that supports a beam or other structure. zCantilever – the part of a beam that extends beyond a column. zFoundation/Footing- distributes the weight of the structure on the ground.

4. Forces Acting Upon A Structure  Compression - A force that attempts to shorten or crush an object or material. Occurs along the top edge of a beam.

5. Forces Acting Upon A Structure  Tension - A force that pulls on an object or material, thereby stretching or elongating it. Tension occurs along the bottom of a beam.

6. Forces Acting Upon A Structure  Torsion- A twisting force.

7. Structural Loads  Dead Load – The weight of the structural elements of the structure  Live Load – The weight of objects placed onto the structure  Static - Stationary Load  Dynamic – A load in motion

8. Types of Bridges  Beam - the earliest and most common bridge form.  Supported at both ends by a pier or foundation.  Strength is accomplished by size and type of material.  Beam bridges rarely span more than 250 feet. SPAN

9. Types of Bridges  Truss - a structural framework consisting of two or more triangles. SPAN

10. Types of Bridges Components: Top Chord - Compression Bottom Chord - Tension Webbing - Compression and Tension

11. Types of Bridges  Arch - carries loads primarily by compression.  Today, most arch bridges are made of steel or concrete, and they can span up to 800 feet.

12. Roman Bridge Building  Roman bridges are famous for using the circular arch form, which allowed for spans much longer than stone beams and for bridges of more permanence than wood.

13. Types of Bridges  Cable Stay - this design carries the vertical main-span loads by diagonal cables in tension.  Cables are attached from the road bed to the tower.

14. Types of Bridges  Suspension Bridge - carries vertical loads through curved cables in tension. These loads are transferred both to the towers, which carry them by vertical compression to the ground, and to the footings which spread the weight over a large area of the ground.

15. Types of Bridges  Cantilever Bridge - generally made with three spans, of which the outer spans are both anchored down at the shore and cantilever(project) beyond a tower.  A beam is said to be cantilevered when it projects outward, supported only at one end.

17. Related Websites http://www.pbs.org/wgbh/buildingbig/bridge/index.html http://www.technologystudent.com/forcmom/force1.htm

18. What Type of Force is being exerted in each example?