pos k1a recognize and classify structural forms and materials used in construction (identify...
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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
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