Post on 22-Dec-2015
StructuresHold, protect & provide shape
Manuel Ángel Martínez García (manuelmg@educastur.princast.es)Jesús Prieto Fuentes (jesuspf@educastur.princast.es)Víctor Manuel Sánchez Canga (victorsc@educastur.princast.es)Grupo de trabajo PALE 2008 – Área de Tecnología
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
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.
ObjectivesAt 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.
Vocabulary
Beam. Joist &Breeze Block
Steel Sections (T, I, …). Columns
Rivets Welding Nuts & Bolts Hinges
What are structures?
Everything has a structure.
A structure is something that 1. Protects.2. Provides shape.3. Supports loads.
What are these structures for?
Functions1. Protects.2. Provides shape.3. Supports loads.
31,2,3
1,2
Structures in Asturias I
Coal washing plant
Saints Bridge (Asturias- Galicia)
Fernández Casado Bridge (Asturias- León)
Cangas de Onís Bridge
Structures in Asturias II
Coal mine shaft
Grandas de Salime dam
Negrón Tunnel (Asturias- León)
Steel Factory cooling tower
Structures in Asturias IIIOviedo
Cathedral
Church in Universidad
Laboral
Viaduct,Luarca
Oviedo Congress Centre
(Calatrava)
Types of structures IMass 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, …
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 StructuresMade by natural means
Manufactured StructuresMan-Made
Loads I
Loads can be either static or dynamic.
Static LoadsThose which remain constant.
Example: the weight of the materials from which a structure
is made.
Dynamic LoadsThose which exert constantly
changing forces upon a structure. Example: a car crossing a bridge.
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.
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.
REMEMBER
1. Structures should operate within the elastic limit of their materials.
2. Structures shouldn’t break under the weight of loads.
3. Structures shouldn’t change their shape significantly under the weight of loads.
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.
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.
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
Loads VI
Compression
Bending
Example
Structural analysis Determine the type of load affecting each piece of a structure
Load
Idea Imagine a piece of the structure breaks. What happens to the pieces?
Load Load
Tension
Compression
Loads VII
Stability (I)
Structures should be stable They should support external loads without falling down, falling over or collapsing.
Unstable building
Unstable slope
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
Stability (III)
c) Anchoring the structure to the floor Using wires.
d) Sticking the structure into the floor Deep foundations
Structural Elements I
ArchesThey 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.
How can we build strong structures?By using resistant structural elements made of light, resistant
materials.
BeamsThese are horizontal elements designed to support bending, produced by vertical forces.
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
Beam
Hollow concrete blocks or breeze blocks, to fill
gaps between joists
Structural Elements III
ColumnsThese are vertical elements designed to support horizontal loads and transmit the forces to the ground.
Foundation elementsThese 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.
Structural Elements IV
ProfilesResistance 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 profileL shaped steel profileU shaped steel profileSteel tube
Structural Elements V
TrianglesVery useful for structures
ApplicationIs it possible to build a structure that supports a book with a piece of card?
Structural Elements VI
SolutionFolding the piece of card forming arcs and triangles.
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
Questions are welcome
Plenary
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)