POS K1a recognize and classify

structural forms and materials used in construction (identify examples of frame structures, such as goal posts and girder bridges, examples of shell structures, such as canoes and car roofs, and examples of frame-and-shells structures, such as houses and apartment buildings.

Unit D: Structures and

ForcesTopic 1 Types of

StructuresTopic 2 Describing

Structures

Careers Associated with this Unit

Engineer Materials/civil/mechanical

Architect Construction/carpenter Project Manager Welder Inventor/Designer Marketing (Lawyers)

Classification of Structures

Two Major types Natural: not made by

humans Manufactured: made by

humans Three sub-types

Mass Frame Shell

Mass & Frame Structures

Mass Structures Can be made by forming

similar materials into a particular shape or design

Mass structures are held firmly in place by their own weight

If small parts break off, it makes little difference

Examples of Mass Structure

Layering in Mass Structures

The pieces that make up mass structures are often carefully arranged

Example: The patterns of bricks in a wall

Mass Structures are not always solid

Ex: Power damns may contain rooms that hold generators

Mass structures must be carefully designed, due their weight and size

Think of a wall of sandbags that is holding back a flooding

riverHow do you think that the

wall structure could fail?

Sandbag Walls Can Fail Because….

The wall may not be heavy enough to stay in place

The wall may be so heavy that the earth below it is pressed down unevenly

The wall may not be thick enough or tight enough, so part of it are pushed out

The structure may not be anchored firmly to the ground

Frame Structures in Buildings

Are a skeleton of very strong materials that support the weight of the roof and covering materials

Most of the inside of the building is empty space

The walls are loading bearing and support the structure

Other FramesSome objects consist only of a frame

More complex objects have other parts added to the frame

Frames may be hidden under covering material

Frames can be left exposed

Problems of Frame Building

• Frame structures are easy to design and build

• One of the least expensive construction choices

• Lightweight frames need to be anchored to the ground

• Very tall frames can become unstable if they are not properly braced

• Large, complicated projects have many parts that all have to fit together perfectly

Shell Structures

Shell Structures• Objects that use a thin, carefully

shaped outer layer of material to provide strength & rigidity

• Strong & hollow• Keep their shape & support loads• Completely empty – make good

containers• Use very little building material• Forces are spread through the

whole structure and each part only supports a small part of a load

Examples of Shell Structures

Problems with Shell Structures

Tiny weaknesses can cause the whole structure to fail

Flat materials are not easily turned into a rounded shell shape

Assembling flexible pieces into a shell can be difficult

Examples(copy this chart, we are going to classify the following structures)

Natural Manufactured

Mass -beaver dam -sand castle

Frame -human skeleton -stool

Shell -turtle shell -cardboard box

Combined type

Sod House(Sod is grass, roots and dirt cut out of the ground in strips)

Epcot Center(Disney World)

Ant Hill(Primarily Sand, some tunnels)

Bird Cage

Snail Shell

House “skeleton”

Describing a Structure Function:

What does it do? What is it for?

Aesthetics Attractiveness of design

Safety Margin of safety- “extra safe”

range Cost (balance with safety)

Materials

Composite materials Layered Materials

Laminations Woven and Knit

Materials

Choosing Materials Cost Appearance Environmental Impact Energy Efficiency

Joints Mobile

Allow movement Ex. Chains, elbows, door hinges

Rigid Fasteners: nails, staples, bolts,

screws Ties: string, rope, thread Interlocking shapes Adhesives Melted joints (welding,

soldering)

Adhesives & Melting

Adhesives

Adhesive (Glue): Sticky substance that

holds stuff together Glue may soften in water

or when its very hot

Melting Welding: Melts pieces

together Soldering: Surrounds

pieces with melted material that locks them together

Assignments Read Topic 2 pgs 282-292,

add to your notes Activity pg 293 “Design

Detective” Traditional Structures Poster

pg 293 Marshmallow Bridge Review Q’s T1-2 pg

296#1,2, pg 297#1,2,3,5,8