Lesson Notes By Weeks and Term v5 - Grade 7
Structures: types of structures and simple frame structures – Week 4 focus
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Structures: types of structures and simple frame structures – Week 4 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Technology
Class: Grade 7
Term: 1st Term
Week: 4
Theme: General lesson support
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This week, we dive into the fascinating world of structures! Structures are all around us, from the houses we live in to the bridges we cross. Understanding how structures are designed and built is crucial for creating safe and functional environments. In South Africa, where infrastructure development is constantly evolving, knowledge of structures is essential for future architects, engineers, and even everyday citizens who want to understand the world around them. Think about the RDP houses, the Gautrain, or even a simple corrugated iron shack - they are all structures with different purposes and levels of complexity.
What is a Structure? A structure is anything that is constructed or built with a definite size and shape for a specific purpose. It can be natural, like a mountain or a beehive, or man-made, like a building or a bridge. Structures must be able to withstand loads and forces applied to them.
Types of Structures: We can classify structures into three main categories: Solid Structures: These structures are made entirely of solid materials. They rely on their own weight and material properties to withstand loads.
Examples include: Brick walls: A solid wall provides support and protection. The bricks are stacked and mortared together to create a strong, solid barrier.
Dams: A dam is a massive solid structure that holds back water. Its weight and shape are designed to resist the huge pressure of the water.
Statues: Sculptures made of stone or metal are solid structures. The shape and material determine their stability.
Mud Huts: Traditional mud huts found in many rural areas of South Africa are excellent examples of solid structures using readily available materials. The thick mud walls provide insulation and support.
Frame Structures: These structures consist of a framework of interconnected members (beams, columns, struts, ties) that support loads. The framework distributes the load across the structure.
Examples include: Bridges: Many bridges are frame structures, using steel or concrete beams and supports to carry traffic across a river or valley. The Gautrain bridge is an excellent example.
Buildings: Modern buildings often use a steel or reinforced concrete frame to support the floors, walls, and roof.
Towers: Cell phone towers and electricity pylons are frame structures designed to withstand wind and other forces.
Shacks: The typical corrugated iron shack, while often considered flimsy, relies on a frame structure - often made of wooden poles or metal - to provide basic support and stability.
Shell Structures: These structures use a thin, curved outer surface to enclose a space and resist loads. The curved shape provides strength and stability.
Examples include: Eggshells: A natural example of a shell structure. Its curved shape allows it to withstand considerable pressure despite being thin.
Domes: The roofs of some buildings are dome-shaped shell structures.
Car bodies: The outer body of a car is a shell structure designed to protect the occupants and withstand impacts.
Igloos: While not common in South Africa, the dome shape of an igloo is a shell structure that provides insulation and structural integrity in harsh environments.
Simple Frame Structures: Focus on Beams, Columns and Joints Frame structures are built from individual pieces joined together.
The key components include: Beams: Horizontal structural members that support loads. They are typically designed to resist bending. Imagine a wooden plank placed across two supports - that's a simple beam.
Columns: Vertical structural members that support loads from above. They are designed to resist compression (being squashed). The pillars supporting the roof of a building are columns.
Struts: Diagonal structural members used to provide stability and prevent deformation of the frame. They resist compressive forces and prevent the frame from collapsing. Imagine the diagonal bars on a bicycle frame.
Ties: Tension members used to hold parts of the structure together. They resist tensile forces (being stretched). Steel cables used to support a suspension bridge are ties.
Joints: The connections between the structural members. Joints can be rigid (fixed) or pinned (allowing rotation). The way these pieces are joined is crucial for the stability of the structure. Think of welding or bolting steel beams together.