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Unit about Structures used for 2º of ESO (Spain)

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  1. 1. What do they have in common?
  2. 2. What do they have in common?
  3. 3. What do they have in common?
  4. 4. Structures Technology Department I.E.S. El Batán, Mieres 2007
  5. 5. Structures Aims: ● Classify the different types of structures. ● Recognize the structural elements than the others. ● Distinguish the different structural forces, specially compression, tension and bending. ● Be able to understand the design of simple structures, attending the forces involved on them.
  6. 6. What's a structure? The structure is the part of an object (a building, a device or a car) which keeps the other parts joined and in their positions.
  7. 7. Where are the structures? Practically all the objects have a structure. Some of them, as bridges, towers, are simply a structure.
  8. 8. Hidden structures Sometimes, as in buildings or cars, the structure is hidden by other elements, but it can be observed during the construction.
  9. 9. Types of Structures Massive: Great amount of mass, stones, concrete or land. Casing or Shell: An exterior box made of rigid material support all the other parts. Framework: Rigid linear elements joined by their ends.
  10. 10. Massive Structures They can use arcs to make the openings. Examples: Great China Wall Egyptian Pyramids Cathedrals Dams Harbours
  11. 11. Arcs The Romans used stone arch technology to build long bridges and high aqueducts. They are widely used in massive structures.
  12. 12. Casing Structures Casing is used in many small objects: as toys, electronics, TV, laptops, mobile phones, etc. Plastic materials are very suitable to make this kind of things.
  13. 13. Frameworks Rigid elements can be made from wood, iron, steel or another metals, or using cement, concrete or reinforced concrete. The triangle is often used to make them stronger.
  14. 14. Why the triangle? If the elements are rigid, even if the joints are articulated, the triangle keeps its shape. Otherwise, square is not a rigid shape.
  15. 15. Trusses & Girders Trusses Girders
  16. 16. Structural elements are subjected to forces (stresses) from the other elements and from the weight of the load. There are six fundamental stresses. They are: Tension Compression Bending (Flexure) We will study some of them. Stresses Shear Torsion Buckling
  17. 17. Tension & Compression Two opposite forces are exerted on the ends of a workpiece. If they are pulling, we say tension. If they are pushing, compression
  18. 18. Flexure, Bending If an horizontal beam supports a load, it's subjected to flexure or bending.
  19. 19. Torsion The element is twisted between both ends, one of them clockwise and another counter-clockwise. The bar is said to be in a state of torsion.
  20. 20. Shear Shear attempts to move adjacent sections of an element in opposite directions.
  21. 21. Beams Beams are used to cross an opening, such as the distance between two walls. They are made from different ‘sections’ or shapes.
  22. 22. Modern Bridges Modern bridges use towers and cables to keep the deck in its place.
  23. 23. Watch the video about the Tacoma Narrows Bridge (1940), and try to explain what you have seen. Look for information in the Internet about it. Study the structure of an Asturian Horreo. Design & construct a 15 cm height structure with paper and cardboard which can support a load of 1 kg. Activities
  24. 24. Analysing a structure 1: Compression 2: Tension 3: Bending 4: Bending & torsion 5: Shear 1 1 1 1 2 2 3 4 5
  25. 25. Credits Made with OpenOffice & LibreOffice running on Knoppix & Ubuntu Linux. All of them are Free Software under GPL License Software. This presentation is licensed under Creative Commons 3.0