1. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Construct a Truss Tower Graphic retrieved from, http://www.world-city- photos.org/Paris/Eiffel_Tow er/Pictures_of_Eiffel_Tower _black_and_white.jpg, on 5/11/2010 Graphic retrieved from, http://www.atlaso.com/imag es/bridge.jpg, on 4/09/2010

2. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Construct a Truss Tower  Performance Objective: Given VEX parts construct a truss tower a minimum of 12” tall, and that will hold a weight ( > 5 lbs) without collapsing.  Enabling Objectives:  define the following terms: force, compression, tension, and shear  identify the forces acting on an object  explain how the geometric shape and orientation of an object can affect the strength of that object or assembly  explain the benefits of using certain geometric shapes over other shapes in the construction of a structure  design a truss bridge

3. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Forces acting on a structure  Force is a pressure on a body or structure  If the force is great enough it will produce a change in movement or in shape of the body or structure  Conceptually, a force can be thought of as a push or a pull acting on a structure or system  In constructing a truss tower, the forces acting on members are compression, tension, and shear

4. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Compression  Compression is a force or pressure that attempts to flatten or squeeze an object Graphic retrieved from, http://library.thinkquest.org/06aug/02102/F orces%20acting%20on%20Bridges.html, on 3/27/2010

5. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Tension  Tension is a force that attempts to pull apart or stretch an object Graphic retrieved from, http://library.thinkquest.org/06aug/02102/F orces%20acting%20on%20Bridges.html, on 3/27/2010

6. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Shear  Shear force attempts to cause the internal material of an object to slide against itself Graphic retrieved from, http://library.thinkquest.org/06aug/02102/F orces%20acting%20on%20Bridges.html, on 3/27/2010

7. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Interaction of forces  When weight is applied to the beam below it experiences compression, tension, and shear forces compression tension shear Graphic retrieved from, http://www.masstec.org/teched/mcasquest ions.html, on 3/27/2010

8. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Forces Applied to Structures  Various geometric shapes can be used in the construction of a structure  Arcs,  Rectangles,  Triangles,  etc.  Different shapes react to forces in different ways

9. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Arches  Arches have a keystone in the middle, that allow the sides of the arch to lean inward, applying a force to the keystone Graphic retrieved from, http://upload.wikimedia.org/wikipedia/ en/7/79/Gateway_Arch.jpg, on 4/09/2010 The Gateway Arch, St. Louis, MO Graphic retrieved from, http://www.dkandsons.com/images/arch%20 with%20keystone.JPG, on 4/09/2010 keystone

10. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Rectangles  Modular apartment buildings are constructed using rectangles Graphic retrieved from, http://jouleconsultingengineers.co.uk/ bigimages/640x480shed.jpg, on 4/09/2010

11. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Triangles  Truss bridges use triangulation to support the weight or force Truss bridges Graphic retrieved from, http://www.prhs.k12.ny.us/fac/Hersko witzM/images/cascade_teft_truss_bri dge_476_1971_ampprn.jpg, on 4/09/2010 Graphic retrieved from, http://www.atlaso.com/images/bridge. jpg, on 4/09/2010

12. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Combinations  What shapes are used in the Eiffel Tower? Graphic retrieved from, http://www.thetravelpeach.com/europ e-vacations/france/eiffel-tower.jpg, on 4/09/2010

13. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Strength and orientation of geometric shapes  Which shape and orientation gives the most structural strength when a force is applied? bar anglechannel

14. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Shape and Orientation  A beam placed vertically is stronger than if placed horizontally  horizontally the bar has very little strength when force is applied  vertically the bar has good strength when force is applied

15. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Bends add support  Notice how this bar flexes or bends when force is applied  An angled shape has strength in two directions due to the bend in the material, minimizing flex as a force is applied. bend in bar

16. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Additional bends  Additional bends in the material create even more strength.  the strength is increased in this channel piece bend in bar

17. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Strength of Geometric Shapes in structures  Which shape gives the most structural strength when a force is applied?

18. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Squares  What happens when you apply a force to the side of a square? No Force Applied

19. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Squares  The square collapses, because it has no strength from side to side. Force Applied

20. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Squares  What happens when your structure utilizes only square and rectangular shapes? No Force Applied

21. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Squares  The structure is not able to hold its shape, and it collapses. Force Applied

22. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Triangles  What happens when you apply a force to the side of a triangle? No Force Applied

23. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Triangles  When force is applied to the side, member A is in tension, while member B is in compression, this allows the triangle to hold its shape. Force Applied A B

24. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Triangles  What happens when you use triangulation in your square structure? No Force Applied

25. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Triangles  When a force is applied, the structure will be able to hold its shape and not collapse. Force Applied

26. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Triangle vs. Square  Notice how the triangle did not lose its shape as the square did when force was applied to the side.  Using triangles in construction offers more structural support for an object than simple squares.

27. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower How does this apply to a robot?  Here is a robot that won a regional competition  What is good about the structural design? Why?  What could be improved? Why?

28. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Robot design  Identify various shapes and structures used in this design.

29. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower Robot design  Here are four possible triangles  Here are various structures Bar with bend Channel

30. Available at: www.etcurr.com Lesson 2.1, Construct a Truss Tower The end  Now don’t get bent out of shape over building your truss tower!