Building Big Structures

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Applied physics / civil engineering

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Building Big Structures

  1. 1. Building Big Structures An overview
  2. 2. Types of Forces <ul><li>Compression </li></ul><ul><ul><li>squeezing </li></ul></ul><ul><li>Tension </li></ul><ul><ul><li>stretching </li></ul></ul><ul><li>Shear </li></ul><ul><ul><li>sliding </li></ul></ul><ul><li>Torsion </li></ul><ul><ul><li>twisting </li></ul></ul><ul><li>Bending </li></ul>http:// www.pbs.org/wgbh/buildingbig/lab/forces.html
  3. 3. Loads <ul><li>Definition: </li></ul><ul><ul><li>Forces that act on a structure </li></ul></ul><ul><ul><li>Structures must withstand loads or they’ll fall apart! </li></ul></ul>
  4. 4. Types of Loads <ul><li>Dead Load </li></ul><ul><ul><li>Weight of structure </li></ul></ul><ul><li>Live Load </li></ul><ul><ul><li>Weight of objects on structure </li></ul></ul>
  5. 5. Types of Loads <ul><li>Settlement Load </li></ul><ul><ul><li>When soil beneath the structure settles unevenly </li></ul></ul><ul><li>Thermal Load </li></ul><ul><ul><li>Heat expands the structure </li></ul></ul><ul><ul><li>Cold shrinks the structure </li></ul></ul><ul><li>Earthquake Load </li></ul><ul><li>Wind Load </li></ul><ul><li>Dynamic Load </li></ul><ul><ul><li>Loads that change over time, like wind or vibrations </li></ul></ul>http:// www.pbs.org/wgbh/buildingbig/lab/loads.html
  6. 6. Withstanding Loads <ul><li>Live Load </li></ul><ul><ul><li>Thicker beams </li></ul></ul><ul><li>Settlement Load </li></ul><ul><ul><li>Deep, heavy piles (in-ground pillars) </li></ul></ul><ul><li>Thermal Load </li></ul><ul><ul><li>Roller joints allow expansion or compression </li></ul></ul>
  7. 7. Withstanding Loads <ul><li>Earthquake Load </li></ul><ul><ul><li>Solid walls of reinforced concrete or masonry (“shear walls”) </li></ul></ul><ul><li>Wind Load </li></ul><ul><ul><li>Steel cross-bracing </li></ul></ul><ul><li>Dynamic Load (vibrations) </li></ul><ul><ul><li>Thicker beams </li></ul></ul>
  8. 8. Materials <ul><li>What you build a structure with matters just as much as how you build it </li></ul><ul><li>Different materials have different properties </li></ul>
  9. 9. Common Building Materials <ul><li>Wood </li></ul><ul><li>Plastic </li></ul><ul><li>Aluminum </li></ul><ul><li>Brick </li></ul><ul><li>Concrete </li></ul><ul><li>Reinforced Concrete </li></ul><ul><li>Cast Iron </li></ul><ul><li>Steel </li></ul>http:// www.pbs.org/wgbh/buildingbig/lab/materials.html
  10. 10. Properties of Materials <ul><li>Wood </li></ul><ul><ul><li>Cheap, strong in compression </li></ul></ul><ul><li>Plastic </li></ul><ul><ul><li>Flexible, lightweight </li></ul></ul><ul><ul><li>Strong in tension & compression </li></ul></ul><ul><ul><li>Expensive! </li></ul></ul><ul><li>Aluminum </li></ul><ul><ul><li>Very strong, lightweight, and doesn’t rust </li></ul></ul><ul><ul><li>Expensive! </li></ul></ul>
  11. 11. Properties of Materials <ul><li>Brick </li></ul><ul><ul><li>Strong in compression, weak in tension </li></ul></ul><ul><li>Concrete </li></ul><ul><ul><li>Molds to any shape </li></ul></ul><ul><ul><li>Strong in compression, weak in tension </li></ul></ul><ul><ul><li>Reinforced concrete is strong in tension </li></ul></ul><ul><li>Steel </li></ul><ul><ul><li>One of the strongest materials in tension & compression </li></ul></ul><ul><ul><li>Rusts and weakens in very high temperatures </li></ul></ul>
  12. 12. Shapes <ul><li>Shape affects strength of structure </li></ul><ul><li>What are the pros and cons of the following common structural shapes? </li></ul><ul><ul><li>Rectangle </li></ul></ul><ul><ul><li>Arch </li></ul></ul><ul><ul><li>Triangle </li></ul></ul>
  13. 13. Shape Lab <ul><li>Prediction: </li></ul><ul><ul><li>Will a triangle or a square be more stable? </li></ul></ul><ul><li>With your partner, build a triangle and a square out of straws and paper clips </li></ul>
  14. 14. Test It <ul><li>Compare the stability of the shapes. Stand each shape up and press down on the top corner. </li></ul><ul><ul><li>What happens? </li></ul></ul><ul><ul><li>How much does each one bend and twist? </li></ul></ul><ul><ul><li>How hard can you press down on each shape before it collapses? </li></ul></ul>
  15. 15. Explain It <ul><li>Compare the results of your tests on the triangle and square. </li></ul><ul><ul><li>Which shape was more stable? </li></ul></ul><ul><ul><li>What do you think made it more stable? </li></ul></ul><ul><ul><li>How might this shape be used in large structures?  </li></ul></ul>
  16. 16. Reinforce <ul><li>Try to reinforce the less stable shape by adding no more than 2 straws and 4 paper clips. </li></ul>
  17. 17. Build It <ul><li>Now that you know more about shapes, build the most stable structure you can using no more than 20 straws and 40 paper clips. </li></ul><ul><li>Can your structure support a textbook? </li></ul><ul><li>Compete for valuable prizes! </li></ul>
  18. 18. Be sure to Turn In your paper in the INBOX!

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