How to use this book Contents
Welcome to Oxford Successful Technology Grade 8. This series is based on the National Curriculum Statement: Curriculum and Assessment Policy Statement issued by the Department of Basic Education. The book is divided into topics that group together the main content that will be done in your Technology class. On the first page of every topic, you will find a mind map that shows you what sub-topics will be covered during the topic. At the end of each topic, you will find a topic summary that will help you to quickly revise the topic’s work.
You will see the following throughout the book:
TOPIC 1 Structures
The modern world in which we live is sometimes referred to as the ‘built environment’ as opposed to the ‘natural environment’. Buildings and structures dominate our cities and, even in the rural areas, we see roads, bridges, communication towers and electricity pylons. All of these structures are designed and built to provide shelter, services and facilities to satisfy our needs and wants. In this unit, we will be looking at some of the important design considerations regarding these structures.
Shell and frame structures • What is a structure? • Identifying different structures
• Structural components • Types of forces in frame structures
Structures
Topic name: Identifies the main content covered in the topic.
Structural members that span a space • Beam bridges • Arch bridges • Suspension bridges • Cable-stayed bridges • Cantilever bridges
Mind map: Unpacks the sub-topics covered within the topic. Sub-topics are separated units within the main topic.
Structural failure • Fracture • Bending • Toppling over • Other supports
Unit name: Identifies the sub-topic that the unit covers within the module.
UNIT 2 Structural members that span a space In this unit you will:
• learn about various types of bridges • study how to make material stronger • build models of bridges.
New word: Explains key words to learn and remember in this subject.
Photographs and illustrations: Are labelled clearly to make it easier for you to understand the text.
Figure 1 A simple beam bridge Beams
A beam is a horizontal member. A beam can be as simple as a plank of wood or it may be made of steel, reinforced concrete, plastic or composite materials.
The main point of weakness in a beam is the fact that they tend to bend downwards under load. This downward pressure squeezes the upper surface (compression) and stretches the lower surface (tension) of the beam. When considering the load on a beam, we need to recognise that the weight of the beam itself contributes to that load. Over the years, many different beam shapes have been developed in order to make them lighter while retaining their strength.
Unit 2 Structural members that span a space 6 Bridges
Bridges are structures that are built to span physical obstacles such as a river or a cliff. The first bridges were made by nature, a log across a stream or stones in a river. The first bridges made by humans were probably spans of wooden logs or planks using a simple support and crossbeam arrangement.
New word
span: to form a bridge over something
6 How to use this book
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