(Under development – to be expanded)
STRATEGIES FOR STRUCTURAL DESIGN
Structural design is a visual process because it begins with the invention or selection of a form and general arrangement for the structure.
2 DESIGN STRATEGY
From the beginning the designer should have a clear idea of his or her intentions.
In particular, a conscious decision should be taken concerning which of the following is to be given the highest priority.
Appearance must be given the highest priority for buildings that are to have symbolic meaning or which are intended to respond directly to the requirements of architectural theory.
If appearance is given the highest priority the built form will almost certainly have a non- or semi-form-active geometry and large quantities of material will be required to provide adequate strength and rigidity, as in this example.
This approach to design is unlikely to produce a low-carbon architecture.
To achieve maximum efficiency a form-active structure will be required. Maximum efficiency is essential if the limits of what is feasible are being approached. This could be due to a requirement for a very long span.
due to a requirement for a minimum weight structure because the building has to be portable.
Low embodied energy and carbon footprint
For low embodied energy the highest priority will have to be the achievement of maximum economy of means. This will involve finding a suitable compromise between complexity of form, that will increase efficiency, and simplicity of form, that will reduce the energy required for design and fabrication. The level of complexity of the structure should be appropriate for the span and loads involved.
Ease of construction
This building is an example of a structure in which ease of construction was a high priority. The primary structural elements are non-form-active pitched trusses, ‘improved’ by triangulation (structural archetypes). Compressive sub-elements have circular, hollow, ‘improved’ cross-sections (another archetype). The high structural efficiency produced by the ‘improvements’ resulted in a lightweight structure that was simple to erect. Solid timber jointing components facilitated assembly.
Judicious use of structural archetypes resulted in a highly practical structure of low carbon footprint.
Availability of materials
This building was constructed from air-dried bricks made from locally available clay. The use of form-active arches and vaults (structural archetypes) to achieve horizontal spans eliminated the need for beams which would have required inclusion of a different (non local) material. The requirement to use a locally available material had a significant influence on the choice of the overall form of the building.
Ideally, all of these design objectives listed above will be satisfied in equal measure, but realistically, one will be given priority and it is important that this is recognized. Where appearance is the highest priority, for example, efficiency and low carbon footprint are unlikely to be achieved.
3 THE DESIGN PROCESS (under development)
The form generated has to be derived from the designer’s knowledge of structural behaviour. The various aspects of this are:
• adherence to structural principles – the most basic requirement of any structure
• application of structural wisdom – a further set of desirable attributes
• judicious use of structural archetypes – which determine the level of efficiency that will be achieved and are the major influence on the selection of form unless aesthetics is the top priority
• articulation – a refinement that affects buildability and aspects of structural behaviour.