How to Build Strong Structures: Strengthening & BRACING

Design & Technology students have to know how to build strong structures that will actually function in the real world. This involves a knowledge of strategies for strengthening joints through the use of triangular trusses, bracing, ribs, flanges, and so on. This article summarises this content and provides sample examination questions to help students revise this material.

STRENGTHENING METHODS

Triangular trusses

Properties

Uses

Triangles are the strongest shape – exceptionally rigid
Excellent strength to weight ratio
Relatively low cost
Very common and versatile structure
Roof trusses
Bridge structures
Tower structures

Bracing

Properties

Uses

Structural members that prevent movement, buckling, and instability
Can be diagonal bracing, shear walls (when a solid wall provides bracing support), or cross bracing (x-pattern)
Resists forces like wind, earthquakes, and user loads
Can be made of different materials, i.e. steel strapping
Angular pieces supporting corners (forming triangles)
Back wall of a bookshelf
Wooden members running between table legs

Brackets

Properties

Uses

Like bracing, but premade bracing components
Often screwed into position
Transfer loads from overhanging or projecting elements back to the supporting structures
Signage supports
Steel brackets to support shelving
Balcony supports

Ribs

Properties

Uses

Thin, raised, repeating, parallel features, reminiscent of rib bones
Provide structural stiffness to surfaces, preventing flexing and buckling, yet lightweight and cost effective
If injection moulded, ribs need draft angles (so easy removal from mould)
Many plastic moulded parts like computer cases, appliances, containers, school chairs
Wooden boat hulls

Gussets

Properties

Uses

Like ribs, but just in the corners
Repeated triangular plates that provide bracing
Steel welded items
Plastic moulded items

Corrugation

Properties

Uses

Stiffens a flat sheet in the direction of the corrugation
Much stronger without adding much weight
Made by passing sheet through fluted rollers
Corrugated iron roofing
Corrugated cardboard

Flanges

Properties

Uses

A projecting flat surface that extends outward from the main body of a structure element
Structural flanges provide structural support in another direction, resisting bending
Pipe flanges provide a flat surface for bolting
Ends of pipes
Top and bottom plates of I-beams, H-beams, and T-beams

Connecting panels

Properties

Uses

Flat panels connecting multiple elements provide bracing, preventing the structure deforming, twisting, or tilting over
Keeps rectangular frame or carcase (structural shell) square and stable
Back panels on bookcases
Plywood panels on buildings / outdoor structures

New Content required in IGCSE (from 2028):

  • Understand the classification and characteristics of natural and manufactured, shell, frame and mass structures
  • show knowledge of static and dynamic loads
  • understand forces that act on structures:
    – tension
    – compression
    – shear
    – bending
    – torsion
  • show knowledge of reinforcement methods used in structures:
    – triangulation
    – corrugation.

Using thicker or stronger material is another way to strengthen a structure, as well as lamination.

Using two fixings in a joint (i.e. two nails instead of one) also makes a structure stronger, as with only one fixing, the two members can pivot and bend much more easily.

Always consider the direction of force / load when designing a structure (for example, the downward force on a table top sitting on table legs).

Sample examination questions (AS Design & Technology)

Examiner comment: Generally, this was answered well. Most candidates could explain the function of Part A with the improvement in structural integrity being part of many responses.

Examiner comment: Almost all candidates stated that one reason for adding a back to the bookcase was to prevent books from sliding off the back. The second reason stated was usually to do with improving the structural stability of the bookcase, giving additional support to the shelves or making the bookcase stronger so that it was able to withstand a force applied to the top corners. A small number of candidates incorrectly stated that that the addition of the back to the bookcase was for aesthetic reasons.

Examiner comment: For the size of the base, most candidates explained that it would need to be large enough to ensure the display stand was stable and would not topple over when in use. Some responses explained that it could not be too large as it would present a trip hazard in a school environment.

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