Don't Forget!

Review the reasons why the Tacoma Narrows Bridge collapsed!

I hope you all have already started to review the material! :)

Designing for Safety Worksheets Answers

Designing for Safety

In this section, you will learn about some of the way in which designers plan safety into structures and the factors they consider when designing and monitoring them.

No one can design a structure to be 100% failure proof. The materials may wear down over time. A person may use it incorrectly and break it. Unexpected forces might come into play

Engineers use the techniques of risk management to reduce the risk of failure as much as possible.

They deal with known risks in one of three ways:

Ignore the risk

Avoid the risk

Design for the risk

When a risk unlikely to occur, it can be ignored. E.g., an elephant sitting on a classroom chair.

Building a bridge with no supports in the water is a way to avoid the risk of boats colliding with the bridge supports.

When designers design for risk they often over-compensate for the various risks. They often make the structure stronger than really needs to be; e.g., stronger bridge supports in the water in case of a boat collision.

They also build in back-up and warning systems that may use sensors.

Designing for Loads

When designing a structure, the designers must calculate the load it will support. They design the chair to support more than itself plus the biggest occasional load. Some structures have warning notices about the maximum load they are designed to support, e.g., an elevator.

The Ontario Building code gives minimum standards for all aspects of building, including load bearing design and materials. This assures the public of a certain level of safety.

The Ontario Fire code is a law in Ontario that states that every home in Ontario must have working smoke alarms on every floor and outside all sleeping areas. Properly installed working alarms can warn people to get out of a burning building. This reduces the number of fire-related injuries and deaths.

Designing for Efficiency

Something described as “efficient” operates well without a waste of time, effort, or expense. E.g., if two students build bridges that support the same load, the bridge that uses the least amount of materials (usually by weight) is considered more efficient.

Sensors

A sensor is any device that can detect or measure real-world conditions. Different sensors can detect heat, lights, pressure, or sound, as well as changes in the amounts of these things.

Make a list of sensors found in your home:

Smoke alarm

Carbon-dioxide alarm

Thermostat

Motion sensing lights

Motion sensor alarm

Chapter 4 Test Study Guide

The following key terms and concepts should be reviewed prior to the test on:

Wednesday October 28th.

Section 4.1 Classification of Structures

1. Form and function
2. Ergonomic design
3. The 3 way to classify structures: form, function, construction
4. The 3 structural forms: frame, solid, shell (many structures are combination structures)

Section 4.2 Forces That Can Act on Structures

5. Internal forces: tension, compression, shear, torsion, (bending - combining tension and compression)
6. External forces: gravity, wind, cars, etc.
7. Describing forces: magnitude, direction, point and plane of application
8. Loads: total load, static load, dynamic load
9. Designing for forces: structures must support total load, a 100-year storm

Section 4.3 Designing for Safety

10. Risk Management:ignore the risk, avoid the risk, design for the risk
11. Designing for Loads: Engineers design for the more than the largest possible load
12. Designing for Safety: Ontario Building Code, Ontario Fire Code
13.Designing for Efficiency: What makes a structure efficient?
14. Sensors: Where are they used? How do they make people safe?

Practice Activities for Forces

Forces Lab

http://www.pbs.org/wgbh/buildingbig/lab/forces.html

Loads Lab

http://www.pbs.org/wgbh/buildingbig/lab/loads.html

4.3 Designing for Safety Quiz and Crosswords Links

Quiz 

https://sciencesource.pearsoncanada.ca/quizzes/quiz_04_3iUc4d.htm

Crossword 

https://sciencesource.pearsoncanada.ca/puzzles/puzzle_04_3/

Forces Notes #5" Internal Forces and Designing for Forces

Internal Forces

·        Can be classified as:

o   Compression – a force that squeezes or presses something together

o   Tension – a force that stretches apart to expand or lengthen

o   Shear – a force that pushes in opposite directions

o   Torsion – a force that twists

o   Bending – A force that acts to bend a component putting one side of the part in tension and the opposite side in compression

The forces occur within the human body as well since the human body is a structure; e.g., when a skater twists, torsion occurs within her body.

Designing for Forces

Engineers have to consider all these forces when designing structures, e.g., they have to consider the load of the snow on a bridge in addition to the truck.  

Engineers design structures to withstand a hundred year storm, a large storm that occurs once in a hundred years. 

Forces Notes #4: External Forces and Loads

Every structure supports a load:

§  Total load: the sum of all the static and dynamic loads

§  Static load: the effect of gravity on a structure (the weight of the structure itself) also called dead load (non-moving things on the structure add to the static load)

§  Dynamic load: the force that moves or changes while active on the structure; also called live load

o   Called “dynamic” because they change their magnitude, direction, and point and plane of application.

o   Wind is considered a dynamic load because its magnitude can change

E.g., a bridge: The static load is the weight of the bridge itself (dead load).

The dynamic load is the weight of the moving cars across the bridge (live load).

DRAW PICTURE OF TRUCK ON BRIDGE WITH LABELS HERE

4.2 Crossword for Practise

You can complete this crossword online AND in your package to practice key concepts.

https://sciencesource.pearsoncanada.ca/puzzles/puzzle_04_2/

Forces Notes #3: Describing Forces

Describing Forces

To describe forces, engineers use three main things:

• The force’s:
• Magnitude (strength)
• The size of force compared to the size and weight of object
• Direction
• Where the force is coming from
• The point and plane of its application
• Point of application: the exact location where the force meets the structure
• Plane of application: the side of the structure affected by the force 

Forces Notes #2: Internal and External Forces

Internal and External Forces

·       External force: acts on an object from outside the object; e.g., wind, gravity, earthquakes

o   Gravity

§  is a natural force of attraction

§  acts on all structures all the time

§  pulls structures towards Earth’s centre

·       other external forces

o   a person on a ladder

o   pulling a drawer open

o   sitting on a chair

o   cars on a bridge

o   wind/snow/rain

·       Internal force: one part of a structure acting on another part of a structure; e.g.,

o   tension in stretched cables on a bridge

o   compression by the weight of a roof on the walls

Section 4.2 Online Practice Quiz

Complete the following quiz to practice the concepts in section 4.2.

https://sciencesource.pearsoncanada.ca/quizzes/quiz_04_2G0jMB.htm

Chapter 4 Test Date

The date for the Chapter 4 Science test is Wednesday October 28th.

Forces Notes #1: Forces that Can Act on Structures

Forces That Can Act on Structures

• Structures constantly experience forces; they must be designed to withstand the forces they will face (Force: any push or pull)
• If the structure isn’t strong enough it may experience structural failure.
• If the structure is too strong, time and resources may have been wasted. 

4.1 Crossword for to Practice Key Terms

You can complete your crossword in the package and check your answers online by following this link!

https://sciencesource.pearsoncanada.ca/puzzles/puzzle_04_1/

4.1 Practice Quiz

You can check your understanding of classification of structures by completing this online practice quiz.

https://sciencesource.pearsoncanada.ca/quizzes/quiz_04_1RHUCb.htm

Classification of Structures Notes

Classification of structures

Structures can be classified by their:

Function – it may contain something (a glass), support something on top (a wall), or span a space (a bridge)

Construction – how they are built and what they are built from

Form – solid, frame and shell structures also there are combination structures

Solid Structures

Most are solid all the way through, but some may have small hollow parts, e.g., an apple or a mountain.

Frame Structures

Made of parts and fastened together; the parts are often called structural components. E.g., a bicycle, a tennis racket, cars, skeleton, umbrellas.

Shell Structures

Strong and hollow structures e.g., an igloo, a domed roof, a glass; these make good containers and require few materials. Even clothes are considered shell structures.

Combination Structures

Combination of frame, shell and solid structures. E.g., a house is made of solid pieces of wood that are arranged in frame. The boards arranged in a frame provided strength to the house.

Form and Function Worksheet Answers

Considering Form and Function _______

Structure	Description of Form	Description of Function
Desk	Made from wood and metal It has a rectangular flat surface with four circular legs	Used to support books, binders and to provide a surface to write on.
Chair	Four legs, sometimes attached to the desk. Made from plastic and metal. Has a back support and a surface to sit on, has four legs	Used to support our bodies in a sitting position
Coat Rack	Made from wood, metal or plastic Its shape is a tall pole with a wider base; there are hooks at the top	Used to hang coats and other clothing, to hang bags
Pen	Made from plastic. Hollow container holds the ink in a stick-like shape.	Used to write with using hands
Bulletin Board	Piece of corkboard attached to the wall with a metal frame.	Used to display work, art or information
Shelves	Made from wood The shape is a rectangular prism open on one side, there are flat wooden boards inside	Used to support books or other objects
Binder	Made from plastic, cardboard, and metal. Plastic covers the outside of rectangular cardboard.	Used to store and organize papers

Made in Bangladesh Video

The following is the complete video we viewed in class as our introduction to structures in the developing world.

Strucutres: Form and Function Notes

Structures: Form and Function

Structure: something made up of parts that are together in a particular way for a specific purpose or purposes

Form: the basic shape of the structure

Function: the job that the structure does

Force: Any push or pull that can make an object change shape, speed, or direction

Ergonomic design: designs that take into account information about the human body. Ergonomic design can help people from getting hurt doing repetitive tasks and those who are physically challenged