Structures

Technology

Grade 9

Architectural planning

Module 6

Structures

Activity 1:

To be able to explain the term ‘structure’.

A structure can be defined as a body that can resist applied forces without changing its shape or size, apart from the deformations due to the elasticity of the materials from which it is made.

In order to design safe, efficient structures we need to understand the effects of forces. The study of forces at rest is called statics , while dynamics refers to the study of forces on bodies in motion.

The main function of a structure is to transmit forces from one place to another. If you sit on a stool, it transmits your weight to the floor. If you walk across a bridge, the bridge transmits the weight to the banks. Objects that serve as structures can have additional purposes.

The walls of a house form a structure for transmitting various forces to the ground but together with the roof they also provide shelter from the elements. Later in this module you are going to design and make an additional building (classroom) for your school. Your design will involve aesthetic as well as technical considerations. You will try to give your structure an attractive appearance so as to enrich the environment.

Focus task A

1. Explain in your own words what a structure is.

2. Give examples of structures in your immediate environment.

3. Make a list of all possible purposes of structures that you can think of. In each case give an example of a structure to explain how the purpose is served.

Activity 2:

To be able to distinguish between different types of structures

Mass structures : These are solid structures such as gravity dams that resist the applied forces by virtue of their own weight.

Frame structures: Bars are joined together at their ends to form a framework, often called skeletal structures. If the bars all lie in the same plane they are termed “plane frames” but if they extend in three dimensions we use the term “space frames”. It is often necessary to cover a space frame with some form of sheet material e.g. a tall building cladded with glass.

Shells : In contrast to frame structures a shell transmits the forces imposed on it through the sheet material of which it is made. Many items like cars were previously designed as a frame (chassis) covered with sheet materials. These days they are designed as shells with the forces being transmitted by the sheet material forming the skin ( monocoque construction ). The shell is often reinforced with stiffeners that help to preserve its shape and thereby add to its strength. A study of the strength of materials is included in engineering courses as a subject called mechanics of solids.

Focus task B

• Make sketches of examples in your environment of the following:

1. Mass Structure

2. Plane frame

3. Space frame

4. Monocoque construction

5. Produce an information sheet on materials that can be used as sheet material for buildings.

6. What does “reinforced” mean?

7. Give examples of reinforced materials.

Assessment

Memorandum

Focus task A

1. Learners must show a clear understanding of what a structure is. Activity 1 explains what a structure is.

2. Any structure from natural to man-made example. Houses, roofs, birds’ nests, bicycle frame, caves, etc.

3. Supports – ladder, chairsProtects – House, birds nestsContains - Swimming pool, shopping bagSpans distances – bridge, washing line

Focus task B

1 Dam walls, reservoirs

2 Bicycle frame

3 Electric power supply tower

4 Car, e.g. Volvo

5. This sheet must contain information on sheet material such as glass, board products, metal products which are used by builders nowadays. The learners need to do research on this assignment.

6. The term means that a material has been made stronger by adding a material of strength in its structure. In most concrete buildings these days metal rods reinforce the concrete.

7. Reinforced concreteWood, e.g. plywoodGlass that contains metal strips