Science Focus Topic 1 Notes: Types of Structures | Print |
Structures are things that have a definite size and shape, which serve a definite purpose or function. To perform its function, every part of the structure must resist forces (stresses such as pushes or pulls) that could damage its shape or size.

Classifying Structures

- not made by people
- occur naturally in the environment

- built by people
- many are modelled after natural structures
Structures can also be classified by their Design

Mass Structures
Can be made by, piling up or forming similar materials into a particular shape or design.

- Mountains, coral reefs are natural mass structures
- Sand castles, dams and brick walls are manufactured mass structures)

Advantages: held in place by its own weight, losing small parts often has little effect on the overall strength of the structure

A Layered Look
- mass structures are not always solid, but are layered and have hollowed out areas for specific functions.
- a power dam and the Great pyramids of Egypt are a good examples

Sandbag Wall Structure to prevent Flooding (4 Key Elements) to avoid failure
- must be heavy enough to stay in place
- must not be too heavy to compact the earth unevenly below it
- must be thick enough so it cannot be pushed out of place
- must be anchored firmly

Frame Structures
Have a skeleton of strong materials, which is then filled and covered with other materials, supporting the overall structure. Most of the inside part of the structure is empty space.

- Load-Bearing Walls: these are the walls that support the load of the the building.
Partition Walls: these are the walls that divide up the space inside the building.
- because they are relatively easy to design and build, and inexpensive to manufacture, the frame structure is the most common construction choice.

A Bicycle frame supports the load it carries on the seat.

Find Out Activity p. 275


Rigid Joint

Mobile Joint


Rigid Shape

Type of Material


All frames, whether simple or complex must overcome similar problems.
To solve these problems joints, type of material, bracing, anchoring and design all must be considered in the overall structural frame construction.

Golf Ball Bridge (Investigation 4-A ? pgs. 276-277)

Shell Structures
Structures, which keep their shape and support loads, even without a frame, or solid mass material inside, are called shell structures. These structures use a thin, carefully shaped, outer layer of material, to provide their strength and rigidity. The shape of a shell structure spreads forces throughout the whole structure, which means every part of the structure supports only a small part of the load, giving it its strength.
Examples include: igloos, egg cartons, turtle shell, food or pop cans, or, even bubbles in foam and cream puffs.

Flexible structures, like parachutes, balloons and different types of clothing are a different type of shell.

Shell structures have two very useful features:

- they are completely empty, so they make great containers
- their thin outside layer means they use very little material

Problems in building shell structures include:
- A tiny weakness or imperfection on the covering can cause the whole structure to fail.
- When the shell is formed from hot or moist materials, uneven cooling can cause some parts to weaken other parts by pushing or pulling on nearby sections.
- Flat materials are difficult to form into the rounded shell shape.
- Assembly of flexible materials is very precise, so that seams are strong where the pieces are joined.

Mix and Match
Some structures are combinations of different types of structures:
- Football helmets are shell structures - to protect the head, with a frame structure attached in front - to protect the face.
Hydro-electric dams are mass structures, with frame structures inside to house the generators
Airplanes are frame structures, with a 'skin' that acts like a shell - giving it the added strength to resist stresses and making it lightweight and flexible.
Domed buildings combine shell and frame construction
Warehouses are often built with columns to support the roof (frame) and concrete blocks, (mass structures) which stay in place because of their weight.

Can you think of some Famous Structures?

Topic 1 Review p. 281