Lesson Notes By Weeks and Term v5 - Grade 7
Structures: types of structures and simple frame structures – Week 1 focus
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Structures: types of structures and simple frame structures – Week 1 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: 1
Theme: General lesson support
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Structures are all around us – from the houses we live in to the bridges we cross and even the chairs we sit on! In South Africa, understanding structures is especially important. We need to build strong and durable houses that can withstand our climate, efficient bridges and roads to connect communities, and even understand how the design of simple objects like market stalls impacts their stability. This knowledge helps us create safer and more functional environments for everyone. This week, we will explore different types of structures and delve into the fascinating world of simple frame structures, understanding how they are designed and how they support loads.
What is a Structure? A structure is something that is built or constructed to support a load. The load is the force or weight that the structure has to withstand. Structures must be strong and stable enough to support their own weight as well as any additional weight or force applied to them.
Types of Structures: There are many different types of structures, but we can broadly classify them into three main categories: Solid Structures: These structures are made almost entirely of solid materials. They rely on their own weight and the strength of the material to support a load.
Examples include: Rock formations (Natural): Table Mountain in Cape Town is a massive solid structure formed naturally over millions of years.
Earth dams: A dam wall made of earth and rock is a solid structure that holds back water. Think of the Gariep Dam.
Brick walls: The walls of many houses in South Africa are solid structures.
Concrete pillars: These are used to support bridges and buildings.
Shell Structures: These structures use a thin, curved outer surface to provide strength and rigidity. The shape of the shell distributes the load across the entire structure.
Examples include: Eggshells (Natural): A fragile but surprisingly strong natural shell structure.
Car bodies: The curved metal shell of a car provides strength and protection.
Water tanks: Large metal or concrete water tanks often have a curved shape for strength. Igloos (although not common in SA, they illustrate the principle): Domes of ice blocks support a significant load.
Frame Structures: These structures are made of a framework of interconnected parts (usually beams, columns, and joints). The framework distributes the load across the different components of the structure.
Examples include: Bridges: The Nelson Mandela Bridge in Johannesburg is a frame structure made of steel.
Buildings: The skeleton of a building, made of steel or concrete beams and columns, is a frame structure.
Cell phone towers: These towers are frame structures designed to support antennas and other equipment.
Bicycle frames: A bicycle frame is a frame structure made of metal tubes.
Market stalls: The frames that support the roofs of market stalls are frame structures, often built from wood or metal.
Simple Frame Structures: Let's focus on frame structures.
They consist of several key components: Struts: These are structural members designed to resist compression (being pushed or squeezed). They tend to be thicker and shorter than ties.
Ties: These are structural members designed to resist tension (being pulled or stretched). They are generally thinner and longer than struts.
Joints: These are the points where different structural members are connected. Joints can be fixed (rigid) or pinned (allowing some movement). The type of joint significantly impacts the structure's stability.
How Frame Structures Work: When a load is applied to a frame structure, the load is distributed through the struts and ties. The struts resist compression, preventing the structure from collapsing inwards. The ties resist tension, preventing the structure from pulling apart. The joints hold the structure together and transfer the load between the struts and ties. The overall stability of the frame structure depends on the arrangement and strength of these components.