Im stucked to the lappy! D:

Structure

Descriptions :

Understand what a structure is and the need for manufactured structures ; anything that can support a load, they must resist force, they must not collapse during use, they must hold parts in the right places.

Understand the four main functions of structure :

Supporting ; chair
spanning ; bridge
containing ; water bottle
protecting ; packaging

Classify structures :

Natural structures

Rib, branches and honeycomb cells.

Manmade structures

Buildings, bridges, roofs and domestic furnitures.

Frame structures

- Frame structures are constructed by joining separate pieces of materials, to support and protect various parts.
- Frame structures are designed to be as strong as possile with minimum material ;
Skeleton, honeycomb, spider webs.

Shell ( skin ) structure

- Shell structures are structures that have a skin to provide their strength ; cups, trashcans.


Structural Bridges

Four main types of bridge:

- Beam bridge
- Arch bridge
- Suspension bridge ; most cables are connected to other cables
- Cable-stayed bridge ; has cables connected directly to towering pylons

Loads

Static load: A force that has constant magnitude, position and direction on or within a structure ; weight of the roof itself.

Dynamic load: A force that changes magnitude, position or direction on a structure ; rain, wind, natural forces.

5 main forces

- Compression
- Tension
- Bending
- Torsion
- Shear

Compressions

- When compressed, structure is squashed
- Force that cause compression are called compressive force.
- Structure in compression ; e.g strut.

Tension

When in tension, structure is stretched.
Force that cause Tension is tensile forces.
Structure in tention ; e.g tie ( all cables, chains, strings )

Bending

When bended, structure is deflected.
Force that cause bending ; bending force.
Structure in compression ; beam, cantilever beam. E.g, diving board, spring board.

Torsion

When under torsion, structure will be twisted.
Force that caused torsion ; Torque.
E.g laundry peg, torsion spring.
Shear

When under shear, one part of structure slide past another part.
Force that cuase shear ; shear forces.
E.g, scissors, hole puncher.

Structural Failure

-Designers must understand the properties of materials so that they can make the right choices in their designs.
-They must understand how a material can change with use.

- A Structural failure may result from one or more of several causes due to :

- Poor selection and wrong use of material.
- A lack of understanding of the forces involved in the design.
- Incomplete knowledge of conditions a structure is likely to face.

Structural Properties of Materials

- The strength of a material is its ability to resist force without breaking.
- The hardness of a material is its ability to resust cutting, scratching or wearing off.

- The elasticity of a material is its ability to return to its original shape after being deformed.

- I beam is very stiff against bending
- Round section tube is very stiff against twisting.

1. It is lighter than solid material
2. It is less expensive
3. Less material, lighter.

Reinforcing Structure

- The triangle is one of the strongest shapes in structural design and does not distort easily.
- Frameworks such as the truss, have triangular parts to provide strength and rigidity.
- Trusses are used for supporting roofs and bridges.

Shelving system is upright with hardboard back in place.

- Sheet material can be stiffened by folding.
E.g , paper.

- Thin sheet materials are quite weak.
- Laminating thin sheet materials together can make them strong.

( 3 sheets of plywood ; standard! )

- Gusset plates are used to add strength a join.
- They increase the area of the joint and help to distribute stress more evenly.
- Gusset plates can be any shape.

- Ribs are used to add strength to the walls of a structure. They help to stop the walls from caving in.

- A sheet of paper can be made stiff by folding into a concertina shape.
- Rolling the paper into a tight tube makes it even stiffer.
- The honeycomb structure is light, but strong under compression

- Braces add strength to a joint.
- Commonly used in shelf brackets, wall brackets.

SPRING!

- Compession spring
- Tension spring
- Torsion spring
- Flat spring

Compression spring

- is used to resist a squashing force ( compressive force )
e.g pens, bicycle suspensions.

Tension spring

- is used to resist a stretching force ( tensile force )
E.g Trampoline.

Torsion spring

- is used to resist a turning force ( Torque)
E.g Laundry peg.

Flat spring

- is a piece of material that returns to original shape when bent.
E.g Stapler.

Screws

- is used to convert rotary motion into linear motion.

THAT'S ALL FOR STRUCTUREEEES~
LEFT ELECTRONICS T_T JIU MING AHHHH!