Structures

1. Manuel ÁngelMartínez García (manuelmg@educastur.princast.es) Jesús Prieto Fuentes (jesuspf@educastur.princast.es) Víctor ManuelSánchez Canga (victorsc@educastur.princast.es) Grupo de trabajo PALE 2008 – Área de Tecnología Structures Hold, protect & provide shape

2. Unit Layout (9 lessons) • Structures (Technology - 2nd Year of ESO) • What are structures? Examples in Asturias. • Different types of structures • Frame, Shell, Solid (or mass). • Types of forces acting on structures • Compression, Tension, Bending, Torsion & Shearing. • Structural elements • Beams, columns, joists, foundations, steel sections, arches, ... • Joints • Rivets, welding, nuts & bolts, hinges, ... • Projects • 3 projects ... • Summary

3. Aims and objectives • Aims • To raise students’ awareness of the role played by structures in common objects. • To show how structures work and how we can use them in our projects. • Objectives At the end of the unit, • Most of the students should be able to identify different types of structure and explain their use. • Most of the students should be able to analyze simple structures and forces. • Some of the students should be able to design simple structures with certain constraints.

4. Vocabulary

5. What are structures? • Everything has a structure. • A structure is something that • Protects. • Provides shape. • Supports loads.

6. What are these structures for? 3 1,2,3 • Functions • Protects. • Provides shape. • Supports loads. 1,2

7. Structures in Asturias I Fernández Casado Bridge (Asturias- León) Coal washing plant Saints Bridge (Asturias- Galicia) Cangas de Onís Bridge

8. Structures in Asturias II Coal mine shaft Negrón Tunnel (Asturias- León) Steel Factory cooling tower Grandas de Salime dam

9. Structures in Asturias III Oviedo Cathedral Church in Universidad Laboral Oviedo Congress Centre (Calatrava) Viaduct, Luarca

10. Types of structures I • Mass Structures • Solid structures which rely on their own weight to resist loads. Examples: a brick, a dam. • Shell structures • Made or assembled to make one piece, usually thin sheet material with ridges or curves to make it stronger. Examples: Tin cans, bottles, car and airplane bodies, …

11. Types of structures II • Frame Structures • These are made from many small parts (called members) joined together. Bridges, cranes and parts of an oil rig are a few examples. Structures can also be classified as Natural Structures Made by natural means Manufactured Structures Man-Made

12. Loads I Loads can be either static or dynamic. Static Loads Those which remain constant. Example: the weight of the materials from which a structure is made. Dynamic Loads Those which exert constantly changing forces upon a structure. Example: a car crossing a bridge.

13. Loads II Loads produce the following effects. Bodies with Elastic Behaviour (elasticity) They change their shape, but return to their original form when the load is removed. Most materials exhibit elastic behaviour to some extent. For example: gently bend a plastic ruler. Bodies with Plastic Behaviour (plasticity) They change their shape, but they don’t return to their original form when the load is removed. For example: bend a paper clip. Up to a certain point, a paper clip will spring back into shape. If you bend it too far, it springs back slightly but stays permanently bent. This means it has been bent beyond its elastic limit.

14. Loads III Bodies with Rigid Behaviour (rigidity) They don’t change their shape when a load is applied. If the load is too heavy, they just break. Example: If you try to bend a piece of glass, you can’t. If you increase the force beyond a certain limit, the glass just breaks. It is said that glass is rigid. • REMEMBER • Structures should operate within the elastic limit of their materials. • Structures shouldn’t break under the weight of loads. • Structures shouldn’t change their shape significantly under the weight of loads.

15. Loads IV Types of Loads  Loads are produced by forces. Depending on these forces, the following effects can be caused: Compression - for example, the buckling of a bridge pier.      Tension - for example, the stretching of a suspension bridge chain or strut                        Bending - compression and extension combined, for example, with a bridge beam.

16. Loads V Torsional or twisting of a bar or a key in the lock Shear ,for example, a bridge beam, a metal shear or a cutting pliers 

17. Loads VI Structural analysis  Determine the type of load affecting each piece of a structure Bending Example Compression Idea  Imagine a piece of the structure breaks. What happens to the pieces? Tension Load Load Load Compression

18. Loads VII

19. Stability (I) Structures should be stable  They should support external loads without falling down, falling over or collapsing. Unstable building Unstable slope

20. Stability (II) We can gain stability in our structures by: a) Choosing an adequate shape flat and wide shapes are the most stable. b) Lowering the centre of mass

21. Stability (III) c) Anchoring the structure to the floor Using wires. d) Sticking the structure into the floor  Deep foundations

22. Structural Elements I How can we build strong structures? By using resistant structural elements made of light, resistant materials. Arches They stop the downward bend of a flat beam. The forces in an arch are transferred to the foundations at the base of the arch. The weight is carried down along two curving paths. Beams These are horizontal elements designed to support bending, produced by vertical forces.

23. Structural Elements II • Joists • These are the horizontal supporting members that run from wall to wall, wall to beam, or beam to beam, to support a ceiling, a roof or a floor. They are made of wood, steel or concrete. • They are often supported by beams and are usually repeated. • Beams are bigger than joists. Joist Hollow concrete blocks or breeze blocks, to fill gaps between joists Beam

24. Structural Elements III Columns These are vertical elements designed to support horizontal loads and transmit the forces to the ground. Foundation elements These are elements designed to reinforce the ground so it can bear the vertical forces produced by the whole structure built upon it. For example footing elements. N.B. Foundations prevent the soil collapsing under the weight of the structure. The weaker the soil, the stronger (and more expensive) the foundations.

25. Structural Elements IV • Profiles • Resistance of structural elements depend on: • The materials used to build the elements. • The shape of the elements. Some shapes (profiles) are stronger than others. I shaped steel profile L shaped steel profile U shaped steel profile Steel tube

26. Structural Elements V • Triangles • Very useful for structures • Application • Is it possible to build a structure that supports a book with a piece of card?

27. Structural Elements VI • Solution • Folding the piece of card  forming arcs and triangles.

28. Evaluation • Learning: • Activities • Exam • Teaching: Pass rate of students • Less than 60%  Unsatisfactory • From 60%-70%  Poor • From 71%-80%  Acceptable • From 81%-90%  Good • More than 91% Very good

29. Plenary Questions are welcome

30. Bibliography & acknowledgements • In this work we have use pictures and taken information from the following sources: • The Internet, specially these sites • http://en.wikibooks.org/wiki/SA_NC_Saaste_Tech:Modules_Structures_grade_5 • http://www.chester.ac.uk/~mwillard/sci_ed/structures/structures.htm • http://www.edselect.com/grade51.htm • http://www.deyes.sefton.sch.uk/Technology/Keystage3/structures.htm#WHAT%20IS%20A%20STRUCTURE? • “Design & Technology”, by James Garratt (ISBN0-521-55607-4)