Unit 4

1. Unit 4 Structures & Forces

2. Unit 4 Topic 1 Types of Structures

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

4. What is a natural structure? • Natural Structure • Something that is not man made • Follows the same definition of a structure

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

6. 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

7. 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

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

9. 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!

10. Frame Structures

12. 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

14. 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

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

16. 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?

17. Shell Structures Cont …

18. 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!

19. 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!

20. 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 shapedindividually • Crazy expensive!

21. Shell Structures Cont … • 4) Assembling the finishing materials into a shell is also very tricky • It needs to be pinned and heldin place in a specificway • Then all the edgesneed special finishing • Crazy expensive again!

22. 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?

23. Unit 4 Topic 2 Describing Structures

24. 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

25. 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?

27. 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 (see pg: 283) • What are the functions of a shoe? • What happens if we try to water proof a shoe?

28. 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!

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

30. 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

31. 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!

32. 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 …

33. 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 concreteConcretepoured over steel rebar (rods).

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

35. 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.

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

37. Factors to Consider • Cost • 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?

38. 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

39. Types of Joints • Mobile Joints • Joints that allow movement • Rigid Joints • Joints that do not allow movement

40. 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.

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

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

43. Adhesives • Adhesives • 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

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

45. Unit 4 Topic 3 Mass & Force

46. 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!

47. 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

48. 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). 1000 mg. equal 1 g.

49. 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.

50. 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!