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### Structures Presentation

1. 1. Structures Technology Department IES Amparo Sanz 1º E.S.O. European Section
2. 2. INDEX <ul><li>Introduction </li><ul><li>Frame structures
3. 3. Shell structures
4. 4. Structural member
5. 5. Redundant member </li></ul><li>What is force? </li><ul><li>Types of loads </li></ul><li>Types of force that act on a structure </li><ul><li>Tension
6. 6. Compression/Pressure
7. 7. Shear
8. 8. Torsion
9. 9. Bending </li></ul></ul><ul><li>Types of structures / Parts of structures. </li><ul><li>Beams
10. 10. Bridges
11. 11. Cantilevers
12. 12. Columns and pillars
13. 13. Ties
14. 14. Struts
15. 15. Triangulation </li></ul><li>Structures and the environment </li><ul><li>Damage to the environment </li></ul></ul>Cover page
16. 16. INTRODUCTION This chapter is about how materials can be formed into different shapes (or structures) to support loads and withstand pressures. Did you know you can make strong structures from fairly weak materials? Most structures are designed to support heavy loads. A bridge is an example of an everyday structure. Can you think of others? When you think of structures, you probably think of things like bridges, mobile phone masts and tall buildings. There are also other examples that we use every day, like chairs, tables, windows and presses. The two main kind of structures are: <ul><li>Frame structure: Frame structures are structures that have a “frame” or skeleton associated with them.
17. 17. Shell structures: Shell structures rely on the shape they have been moulded into for their strength. They are usually lighter than frame structures. </li></ul>These structures may be man-made or may occur naturally . Cover page
18. 18. FRAME AND SHELL STRUCTURES Cover page
19. 19. Structural Members STRUCTURAL MEMBER A structural member is a part of a structure. Tension Compression Redundant REDUNDANT MEMBER A redundant member is a part of a structure that is neither in tension nor compression. Redundant members can be removed from structures without the structure weakening. A good design has not redundant members. Cover page
20. 20. What is a force? A force is a push or a pull . Forces can make things move. Engines and motors make forces that cause machines to move. The force of gravity pulls everything downwards towards the earth. Force is measured in newtons (N), after Sir Isaac Newton. TYPES OF LOADS: Structures are built to support a load. Loads can be static (not moving) or dynamic (moving) Cover page
21. 21. Types of forces that act on a structure <ul><li>Tension
22. 22. Compression / Pressure
23. 23. Shear
24. 24. Torsion
25. 25. Bending </li></ul>Cover page
26. 26. Tension Tension is stretching, straining, pulling, tensile force. If something in tension is cut, the two ends will pull apart. <ul><li>Example: A rope with a weight hanging on the end of it is in tension. If it cut, it will pull apart.
27. 27. Example: A coping saw always has its blade in tension. If the blade is cut, it will pull apart. </li></ul>Cover page
28. 28. Compression / Pressure Compression means being pressed into less space or being flattened by pressure. Something under a heavy load is in compression. Certain materials under compression will get smaller. An object is under pressure if there is a compression force acting on it. Pressure = Force / Area This means that the smaller the area the force is applied to, the greater the pressure. This explains why someone leaning on you with their hand is a lot less painful than the same person leaning on you with a compass point. Cover page
29. 29. Shear A shearing force is a tearing or ripping force that is trying to move one part of the material in the opposite direction to the other. <ul><li>Example, scissors cut through paper by applying a pair of forces on the paper, each force in the opposite direction. </li></ul>Shear force acts on the paper as the scissors try to cut through it. Cover page
30. 30. Torsion Torsion is the act of twisting a structure. A torsion force causes something to twist or turn. The cube is in torsion, as it is being twisted. Cover page
31. 31. Bending Forces can bend a structure. Example: A bar bends due to the weight of a gymnast swinging on it, or a long narrow shelf may bend with books on it. In these situations, the upper surface is in compression and the lower surface is in tension. The beam is being bent with the weight. Cover page
32. 32. Types of structures / Parts of structures <ul><li>Beams
33. 33. Bridges
34. 34. Cantilevers
35. 35. Columns and pillars
36. 36. Ties
37. 37. Struts
38. 38. Triangulation </li></ul>Cover page
39. 39. Beams A beam is a long rigid piece of wood or metal. It is the simplest way of supporting a load across a gap. It is the simplest structure, but it can also be part of a more complex structure. Circular section Square section Triangular section L-section beam I-section beam U-section beam T-section beam Cover page
40. 40. Bridges A bridge is used to “bridge” a gap, usually between the banks of a river. A bridge has supports at two ends. The first bridges were simple wooden beams, but nowadays they are often huge, complicated structures. Golden Gate (St. Francisco) Tower Bridge (London) New River Gorge Bridge Fayetteville (USA) Cover page
41. 41. Cantilevers Cantilevers are beams that are held and supported at one end only. They are brackets for supporting balconies, shelves, tree branches, etc. Cover page
42. 42. Columns and pillars Columns and pillars are vertical beams, normally designed to support loads directly on top. Example: Table legs. Cover page
43. 43. Ties A tie is a part of a structure in tension for keeping two objects from spreading or separating. Ties are usually thin. Example: The cross piece on a swing. Tensor Cover page
44. 44. Struts A strut is a part of a structure in compression for keeping two objects from coming closer together. Struts are usually thick. Example: A pillar supporting a roof. The wires on either side of the flagpole are being stretched, and so, therefore, are the ties. The pole is in compression due to gravity, and so, therefore, is the strut. Cover page
45. 45. Triangulation Triangulation means using triangles arranged together to form a frame or part of a frame, with increased rigidity . Structures made from triangles are strong. Eiffel Tower Pylon Tecnology Project Cover page
46. 46. Structures and the environment While many structures are needed in our world to house people and allow them easy transport, structures also impact on our environment. Structures can impact positively by being beautiful and enriching people's lives or structures can be ugly and damage the environment. DAMAGE TO THE ENVIRONMENT The environment can be damaged from structures being built in some or all of the following ways: <ul><li>Grassland is destroyed by the structure.
47. 47. There is pollution from the lorries and trucks used in the construction of the structure.
48. 48. The iron, stone and other raw materials have to be sourced in quarries and mines, which damage the landscape. There is further environmental damage in converting the raw materials into a form that can be used in the structure.
49. 49. Wildlife is disturbed and may no longer survive. </li></ul>Cover page
50. 50. THE END Cover page