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 Forces Topic 1 Types of Structures Topic 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 river How 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 Frames Some objects consist only of a frame More complex objects have other parts added to the frame

Frames can be left exposed 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

Natural Manufactured Mass Frame Shell Combined type 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 is grass, roots and dirt cut out of the ground in strips) Sod House (Sod is grass, roots and dirt cut out of the ground in strips)

Epcot Center (Disney World)

(Primarily Sand, some tunnels) 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 Rigid 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

Sticky substance that holds stuff together 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