1. Unit 5 Structural Strength & Stability
Chapter 13 Describing Structures and their construction

2. Structure and Functions
 Manufactured structures: are made by people
Natural structures: are not made by people
Function or purpose: To perform its main job every part of the structure must resist forces that could change its shape or size.
*Ex: you might build a brick wall around your backyard. The wall must be able to stand up to the force of the wind. The bricks at the bottom must support the weight of the bricks above.

3. Types of Structures
-mass structures: sand castles and other things build by piling materials up or called mass structures
frame structures: like the Houses many buildings are frame structures. load bearing walls hold up a frame structure.
*Load: the weight carried or supported by is structure

4. Structures and Criteria
- shell structures are objects that use a thin, carefully shaped outer layer of material to provide their strength and rigidity. * for example: egg cartons, food cans and bottles pipes and clay pots are all examples of shell structures - criteria or specifications: these tell how well must a structure perform its function. it gives a precise measurable standard that structures must meet.

5. Structural tools
- braces, ties and gussets: these turn rectangular corners in to rigid triangles, able to resist large forces. * whole buildings can be made with triangular sides creating a pyramid shape.
- aesthetics is the study of beauty in art and nature

6. Structural Tools
Arch: carries load forces all the way to the ground. domes use this principle to spread forces evenly through the whole structure and down to the ground.
Columns and horizontal beams: are weak in the middle. Pressing down on the middle of the beam causes it to bend and push sideways. If the supporting column spread apart the structural collapse.
Double cantilever: is a particularly strong design with a very strong central column and braces that support beams on either side.

7. Structural Materials
laminations: to make the material of layers that are glued or pressed together.
corrugated: in plywood the fibers in different layers point in different directions. cardboard has a middle layer that is folded into a wave like or corrugated shape.
composite materials: are created by pouring concrete around steel rods and mesh.

8. Structural Joints
Rigid joint: these fasten parts firmly together, but these two can be weak points in a structure. chair legs and table legs become wobbly as wooden parts shrink, glue ages, or nails, screws and bolts and loosen.
Mobile joints: are joints that allow movement. example door hinges, elbows and pins in a bicycle chain.

9. Structural Joints
Brazing and soldering: surround pieces with a different melted material which locks the pieces together as it cools and hardens.
Adhesive or glue can hold things together these are sticky substances. - Welding :melts the pieces themselves.