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 common 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
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
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, force on a table tops sitting on table legs).
Amiria has a Bachelor of Architectural Studies, Bachelor of Architecture (First Class Honours) and a Graduate Diploma of Teaching. She is a CIE Accredited Art & Design and Design & Technology Coursework Assessor. Amiria now teaches Art, Design & Technology at ACG Parnell College.
