Unit D: Structures and Forces
(Science and Technology emphasis)

7 Wonders of the World
Great Buildings of the World

Overview:
Structures can be found in both natural and human-constructed environments, serving a variety of purposes and taking a wide range of forms. In learning about structures students investigate the properties of materials used, and test them under different loads and forces. They examine different ways that structural components are configured, analyze forces involved and investigate resulting effects on structural strength and stability. As part of their study, students also examine construction methods used in past and present, and learn how science and technology link together in developing safe and efficient designs that meet human needs.

Focusing Questions:
How do structures stand up under a load?

What forces act on structures,
and what materials and design characteristics contribute to their strength and stability?

Key Concepts

	recognize and classify structural forms and materials used in the built environment (e.g., 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-shell structures such as houses and apartment buildings)
	interpret examples of variation in the design of structures that share a common function, and evaluate the effectiveness of the designs (e.g., compare and evaluate different forms of roofed structures, or different designs for communication towers)
Native American Shelters	describe and compare example structures developed by different cultures and at different times, and interpret differences in functions, materials and aesthetics (e.g., describe traditional designs of indigenous people, and peoples of other cultures; compare classical and current designs; investigate the role of symmetry in design)
	describe and interpret natural structures (bone), including the structure of living things and structures created by animals (e.g., skeletons, exoskeletons, trees, bird's nests)
	identify points of failure and methods of failure in natural and built structures (e.g., potential failure of a tree under snow load; potential failure of an overloaded bridge)

	recognize and use units of force and mass, and identify and measure forces and loads
	identify examples of frictional forces and their use in structures (e.g. friction of a nail driven into wood; friction of pilings or footings in soil; friction of stone laid on stone)
	identify tension, compression, shearing and bending forces within a structure and describe how these forces can cause the structure to fail (e.g., identify tensile forces that cause lengthening and possible snapping of a member; identify bending forces that could lead to breakage)
	analyze a design and identify properties of materials that are important to individual parts of the structure (e.g., recognize that cables can be used as a component of structures where only tensile forces are involved; recognize that beams are subject to tension on one side and compression on the other; recognize that flexibility is important in some structures - earthquake-proofing structures)
	infer how the stability of a model structure (dam) will be affected by changes in the distribution of mass within the structure and by changes in the design of its foundation (e.g., infer how the stability of a structure will be affected by increasing the width of its foundation)

	devise and use methods of testing the strength and flexibility of materials used in a structure (e.g., measure deformation under load)
	analyze methods of jointing used in structures, and evaluate the appropriateness of a particular type of joint to an individual structure (e.g., fixed jointing by welding, gluing or nails; hinged jointing through pin joints or flexible materials)
	compare structural properties of different materials, including natural materials and synthetics
Biominerals	investigate and describe the role of different materials found in plant and animal structures (e.g., recognize the role of bone, cartilage and ligaments in vertebrate animals, and the role of different layers of materials in plants)

	describe and demonstrate methods to increase the strength of materials through changes in design (e.g., corrugation of surfaces, lamination of adjacent members, changing the shape of components, changing the method of fastening)
	identify environmental factors that may affect the stability and safety of a structure, and describe how these factors are taken into account (e.g. recognize that snow load, wind loads and soil characteristics need to be taken into account in building designs; describe an example of design adaptations used in earthquake-prone regions)
	analyze and evaluate a technological design or process on the basis of identified criteria such as costs, benefits, safety and potential impact on environments