SYSTEMS AND CONTROL
4.2 Structures 4.2.3 Strengthening frame structures Learning objectives By the end of this unit students should: ● understand how triangulation can strengthen a frame structure ● understand how bracing and gusset plates strengthen structures at their corners.
Key terms space frame, triangulation, truss
Resources Student Book pages 240–241 Activity sheets A–B (available online on Collins Connect) Drinking straws or similar materials, tools to cut and shape the straws, glue
Lesson ideas The Student Book and Teacher resources have been designed to be used flexibly, either off-the-shelf in their printed format, or they can be easily adapted and customised by the teacher to better meet the needs of individual classes. In this unit, you will find an outline of lesson ideas and suggestions for learning activities for Unit 4.2.3. The activities in this unit are designed to develop understanding of how frame structures can be strengthened by using the principle of triangulation and strengthening the corners of the frames, e.g. cross-bracing and gusset plates. It is suggested that one lesson should be devoted to this unit.
Lesson starter suggestions Skills activity (page 240): Ask students to do the first part of the activity. This involves making a rectangular frame out of drinking straws and exploring how the frame deforms under squeezing and pulling loads. Students can strengthen their frame using a triangulation member that connects the corners of the rectangle. They then note the effect of the cross member in strengthening the framework when it is loaded.
Main lesson activities Teacher-led discussion (1): Ask students to read about triangulation on page 240 of the Student Book. Make sure they understand the principle of triangulation. Emphasise that the concept is widely used in the design of frame structures to add rigidity and strength. You can use photos of common structural examples like bridges, buildings and bicycle frames to show students how triangulation is used in a range of Design and Technology applications. Skills activity (page 240): Ask students to do the second part of the activity. This involves exploring how cross-bracing and gusset plates are commonly used to strengthen the corners of frame structures. Teacher-led discussion (2): Discuss with students how cross-bracing and gusset plates are used in practice. Emphasise how the strengthening methods are used in the design of frame structures to add rigidity and strength. You can use photos or material from the internet to show students examples of the use of cross-bracing and gusset plates, e.g. in frame structures such as bridges, gusset plates are often
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Cambridge IGCSE Design and Technology Teacher Guide © HarperCollinsPublishers Ltd 2016