1. Unit 4
Structures & Forces

2. Topic 1 Types of Structures
Unit 4
Topic 1
Types of Structures

3. What is a structure?
Structure ??

4. What is a structure? Structure
Something with a definite shape and size which serves a definite function or purpose

5. What is a natural structure???
Follows the same definition of a structure

6. What is a natural structure?
Something that is not man made
Follows the same definition of a structure

7. What is a manufactured Structure???
Follows the same definition of a structure

8. What is a manufactured Structure?
Something that is created by man
Follows the same definition of a structure

9. What is a Mass Structure
A structure made by piling up, or forming, similar materials into a particular shape or design – can be natural
Follows the same definition of a structure

10. How can a mass structure fail?
There are 4 ways a mass structure can fail …
Let’s use a sandbag wall for example!
But …
Before I reveal them can you think of the 4?

11. How can a mass structure fail?
There are 4 ways a mass structure can fail …
Let’s use a sandbag wall for example!
1) The wall is not heavy enough and forces on it push it over
2) The wall could be too heavy, move the earth underneath it, it becomes uneven and topples
3) The wall could be put together poorly resulting in weak links. Certain pieces fall out and wall falls
4) Not anchored to the ground and the external forces will knock it over

12. What would a load be? Load
Weight carried or supported by the structure

13. Frame Structures What is it? A structure with a skeleton like frame
Always made of strong materials
Can support huge amounts of weight … if built properly of course!

14. Frame Structures

16. Frame Structures Cont …
All frame structures are not the same
Objects such as ladders, snowshoes and spider webs are only frames
That is to say are full of important pieces
More complex objects often attach things to the frame
Think a bike … frame is what you sit on and it supports you but we add…
Braking system
Steering system
Suspension systems
Pedals

18. Frame Structures Cont …
Frames can also be hidden …
Like in an umbrella or a car
Or exposed (out in the open)
Like a drilling rig or bridge

19. Shell Structures Strong and hollow Keep their shape
Support loads even without a frame or solid mass of material inside

20. Shell Structures Cont …
2 Major Benefits of this structure
Based on what we just discussed for frame structures … what would the benefits of a frame structure be..?

21. Shell Structures Cont …
2 Major Benefits of this structure
1) They are completely empty which makes them great containers
2) They are made up a thin layer they use very little building materials
But how does it work?

22. Shell Structures Cont …
Shell structures are great! I know shell structures. I’m the best with shell structures

23. Shell Structures Cont …
So if they are cheaper and very strong – why don’t we build everything into a dome shape?!
As strong as they are they face many different challenges to be constructed perfectly!
1) Tiny weaknesses cause the whole structure to fail!

24. Speaking of balloons …

25. Shell Structures Cont …
2) If it is formed and constructed out of hot or moist materials (think clay for example) and dries or cools unevenly you can push or pull in neighboring sections
This causes structural weak points and out of no where it could break!

26. Shell Structures Cont …
3) Think of trying to build a plywood igloo!
Many of our construction materials are not designed for this type of construction
Each piece would need to be shaped individually
Crazy expensive!

27. Shell Structures Cont …
4) Assembling the finishing materials into a shell is also very tricky
It needs to be pinned and held in place in a specific way
Then all the edges need special finishing
Crazy expensive again!

28. Mix & Match
To make the best of both worlds many structures in the world mix and match the principles of both designs together
Part Frame Structure
Part Shell Structure
How does this work?

29. Topic 2 Describing Structures
Unit 4
Topic 2
Describing Structures

30. Functions
Structures perform a variety of different jobs … here is a list of the most common.
Can you think of a real world example of each?
Containing
Transporting
Sheltering
Lifting
Fastening
Separating
Communicating
Breaking
Holding

31. Functions The first thing all designers/builders think is …
“What is this thing supposed to do”
However is it that simple?
No way!
Structures often have many different functions
What are the functions of a house?
What are the functions of a bridge?

32. So what is this..?

33. Functions Cont…
Often, as much as we want the designs to be perfect, when we add multiple functions they are not perfect
Think of a shoe
What are the functions of a shoe?
What happens if we try to water proof a shoe?

34. Aesthetics What are aesthetics?
How good it/they look of course!
Aesthetics is actually the study of beauty in art and in nature
Building materials are key in this? Concrete vs. Marble?
Also, remember the KISS principle
Keep It Simple Stupid!

35. Safety Picture an elevator … or look at this! 
What is the key thing on this panel?

36. Safety Picture an elevator … or look at this! 
What is the key thing on this panel?
All structures are designed with safety in mind!
Elevators are designed to hold more than it could fit for safety

37. Safety
Elevators have extra strength that allows it to withstand much larger loads than it would normally need to carry
Large safety margin! Safe for riders in almost all situations

38. Balance Making things safer typically means more expensive
Sometimes … builders / designers try to take the easy way out and cheap out – no good!
Also, designs typically take into account events they assume will occur (flood, wind, etc …)
Rare and unexpected events are tough to plan for because there are so many things that could happen!
Oops!

39. Materials
So … as you have seen there is a lot of thought that goes into designing something.
Once you have a design it is time to determine what type of materials you will use to construct it
Let’s explore the most common categories …

40. Composite Materials There are different kinds of strength…
Tension (pulling)  Steel rods
Compression (pushing)  Concrete
To enable the structure to withstand both types of forces acting on it, a composite material is used
Composite is essentially a combination of materials
Reinforced concrete  Concrete poured over steel rebar (rods).

41. Layered Materials Pressed and glued together
Combining the properties of the different materials.
The layers are often called laminators.
Did you know this about pop cans and canned foods?

42. Woven / Knitted Material
Spinning or twisting, looping or knotting fibers together gives material added strength
A loom is used to weave two or more pieces of yarn together in a criss-cross pattern to make cloth
Pressing, gluing, melting and dissolving are also ways to combine materials to gain strength.

43. Choosing Materials When choosing materials it is about … For example…
Weighing advantages vs. Disadvantages
For example…
Higher quality & stronger materials are usually more expensive
So here are the most common factors to consider!

44. Factors to Consider Cost
Will inexpensive materials allow the structure to perform its function over a reasonable time?

45. Factors to Consider Appearance
Is the appeal of the structure ‘pleasing' over time?

46. Factors to Consider Environmental Impact
Does the structure harm the environment

47. Factors to Consider Energy Efficiency
Does the structure conserve energy?

48. Factors to Consider Cost Appearance Environmental Impact
Will inexpensive materials allow the structure to perform its function over a reasonable time?
Appearance
Is the appeal of the structure ‘pleasing' over time?
Environmental Impact
Does the structure harm the environment
Energy Efficiency
Does the structure conserve energy?

49. Joints How would you define “Joint”
How do you fasten the structure together?
Are there different kinds of joints?
All this and more on today’s lesson …
JOINTS

50. Types of Joints Mobile Joints Rigid Joints Joints that allow movement
Joints that do not allow movement

51. Fastening
Fasteners 
Devices that hold two, or more, things together
Ex: nails, staples, bolts, screws, rivets and dowels
Unfortunately, the holes made in the structure, by the fastener, actually weaken the structure
One fastener allows movement when the parts are pushed or pulled
More than one will make a more rigid joint - but, will also weaken it more.

52. Interlocking Interlocking shapes Examples
Fit together because of their shape
Examples
Dovetail joints in drawers, dental fillings, Lego

53. Ties Ties Examples Essentially a form of fastening
Thread, string and rope

54. Adhesives Adhesives Thermosetting glues  hot glue
Sticky substances can also hold things together. 
Thermosetting glues  hot glue
Solvent-based glues  drying glue
Strengthen the joint because of the bonds between the particles
Even the strongest adhesives can fail under extreme conditions … if the joint is stronger than the material it is joining, the material next to the joint can fail.
Adhesives can also be a health hazard

55. Melting Melting Examples
Pieces of metal or plastic can be melted together
Examples
Welding, soldering - brazing or using chemicals

56. Unit 4
Topic 3
Mass & Force

57. Mass vs. Weight
So this is the time we learn something very important …
… that is what is mass?
… that is what is weight?
Let’s go!

58. Mass Think back to the particle theory!
All things are made up of particles right?
Can you guess where I am going with this…?
The mass of an object is the measure of the amount of matter in it
The mass is the number of particles the substance has

59. Mass – Units of measure?
To set the standard … A small cylinder of metal was used by which, to compare different substances.
This standard (in the metric system) is called the primary standard of mass, and the amount of material in it is called one kilogram (kg).
Smaller masses are measured in grams (g).
'Kilo' means one thousand (1000) and is equal to 1000 grams.
Very small masses are measured in milligrams (mg) mg. equal 1 g.

60. Mass – The Standard to Measure
A balance is used to measure the amount of mass in a particular substance
Standard scientific balances include the triple beam balance and the equal arm balance.

61. No matter where you are in the universe your mass stays the same!
Mass – In summation
How much would your mass be on Earth compared to the moon?
Trick question it stays the same … the big idea is…
No matter where you are in the universe your mass stays the same!

62. Forces & Weight Force is a push or pull on an object
The standard unit of force is called a Newton (N)
(1 newton of force will stretch a thin rubber band, or will be what it takes to lift up a D-cell battery)
A force meter (spring scale) is used to measure the amount of force - the pull of gravity - on a mass.
To describe a force accurately, you need to determine its direction and size.

63. Weight & Gravity
Time to play with spring scales!

64. Weight Weight is a force and should properly be measured in newtons
Sir Isaac Newton described the force that pulls objects together as the force of gravity
The gravitational forces between two objects depends on the masses of the objects and the distance between them
This gravitational force is called weight
Because gravitational force depends on the distance between two objects, an object's weight changes depending on where it is. (the farther away from the earth, the less the weight.

65. Mass is the amount of matter an object is made of
Remember!!
Mass is the amount of matter an object is made of
Weight is the force with which gravity pulls on an object.