Knowledge of structures CMT 8-5
A structure refers to framework that is used to support a load(s). A framework is comprised of structural members that are assembled using pin or fixed joints. The integrity of a framework is reliant on the strength, weight, material, and profile of its structural members; the combination and means of joining structural members; and the safety factors applied to the structure.
Knowledge within this component includes understanding of how pin jointed structural members transfer forces when a framework is subjected to gravitational loads; how safety factors are applied to ensure a frameworks integrity; and calculating using vector diagrams the magnitude, direction, and type of force acting on pin jointed structural members in a framework.
Learning objective: CMT 8-5
Students will:
- demonstrate understandings of complex structures.
Indicators
- Uses technical language, diagrams, and symbols to explain structural members and materials used in a structural system, and how the system withstands known loads.
- Discusses how the selection of structural members and materials enables a structural system to achieve structural integrity in terms of withstanding known loads.
- Evaluates the structural integrity of a structural system.
- Discusses, with justification, possible ways of increasing the structural integrity of a structural system.
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Progression
Initially students learn what is meant by tension, compression, shear, and torsion; how safety factors are applied in the design of frameworks; how structural members and pin joints transfer forces in a framework; and how the integrity of a framework is established. This should progress to students learning how to: use technical language, diagrams, and symbols to explain structural members and materials used in structural systems such as buildings, bridges, cranes; explain the way structural members and materials enable a structural system achieve structural integrity through withstanding known loads; and evaluate the structural integrity of a structural system; and determine ways of increasing the structural integrity of a structural system.
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Teacher guidance
To support students to understanding complex structures at level 8, teachers could provide opportunity for students to:
- understand how dynamic loads (that is, those resulting from changes in heat, wind and earth movement) impact on the design of structural systems (for example buildings, bridges, cranes).
- use technical language, diagrams, and symbols to explain structural members and materials used in structural systems, and how these systems withstand known loads
- understand how the selection of structural members and materials enables structural systems to achieve integrity in terms of withstanding known loads across a range of differing structural systems
- evaluate structural systems and discuss, with justifications, possible ways of increasing the structural integrity of structural systems across a range of differing structural systems.
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Contexts for teaching and learning
The assessment resource uses the context of a timber house built for current New Zealand conditions. Students would need to explore information that supports their understanding of how a timber-framed house derives its structural integrity situated in different topographical, wind, and earthquake conditions in New Zealand and when different roof types and materials are used, for example, corrugated iron versus clay tiles. In doing so students would need to learn about the implications of structural changes, including in materials and construction techniques that are needed for differing conditions. This could be done by comparing different locations and topography for example comparing a coastline property versus a metropolitan situation, hillside site versus a flat site, or a house on a property in an earthquake-prone area versus a non-earthquake-prone one. As part of this learning students should become familiar with the relevant building codes and New Zealand standards.
This learning could be part of design work where they are engaged in learning about and presenting information regarding the design of structure where they are designing a timber-framed house to address an identified need or opportunity or as a separate research investigation. The design work is not part of their assessment but may contribute to other portfolio of evidence for other standards. In this case students are assessed on their understanding of the structural system within their design and in other structures for example New Zealand timber-framed houses.
Literacy considerations
Students will be required to:
- research appropriate materials to gather and analyse relevant information
- explain and discuss aspects related to structures, load, and materials in context
- evaluate the integrity of a structural system
- discuss and justify possible ways of increasing the structural integrity of a structural system
- presentation of evidence may be in the form of a report that includes discussions and an annotated graphic design, and may include annotated photographs and CAD drawings.
Resources to support student achievement
Students will need access to visiting speakers such as architects, builders, and council building inspectors and technical information such as:
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Assessment for qualifications
The following achievement standard(s) could assess learning outcomes from this learning objective:
- AS91624 Construction and mechanical technologies 3.24: Demonstrate understanding of a structural system
Key messages from the standard
For the purposes of this standard a structural system refers to any technological outcome where the structural integrity is of primary concern. Examples of structural systems include such things as:
- bicycles
- cars
- aircraft
- buildings
- bridges
- cranes
- marquees
- bodices
- sails
- scaffoldings
- staging
- lighting and/or sound rigs.
Dynamic loads acting on a structural system may include those resulting from changes in heat, wind, velocity, g-force, tension, and earth movement.
Last updated May 23, 2018
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