Enabling architects to develop structure early in design

One way of enabling architects to get structural input in their architectural design in the early stages is by providing adequate software tools. It is not the aim of this research to make architects into structural engineers or experts in

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101 structural design. The software should enable architects to request specific

structural information for their design.

A lot of structural engineering software is already available that can precise-ly calculate any required dimension of a structural element. But this software requires specific engineering knowledge to operate correctly. Because the re-quired structural information process does not need to be as precise as this software requires for an architect early in a design, it should be possible to have some pre-dimensioning through elementary input by the architect.

Figure 5-2. Undeveloped tool: floor height versus span for a load of 3.5 kN/m². In order to understand what inputs are required and what outputs can be ex-pected of such pre-dimensioning software, an explorative investigation is de-veloped. Data is produced that links the span of a floor and its material and form with its height. The intention is that an architect would design a floor, and by choosing the span and type of floor get an estimate of the thickness of the structural slab. To enable this, certain structural variables need to be cho-sen and fixed in advance, such as the structural quality of the materials, the fire resistance of the floor and the load. One of the problems that occur in es-tablishing this structural data is determining these fixed variables. For exam-ple, in Belgium buildings with wooden floor joists are typically finished with lightweight wooden surfaces, while concrete slabs can have a heavier finish such as ceramic tile flooring. And thus in general the wooden floor system

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RC Hollow-Core Slab + 0 cm RC Hollow-Core Slab + 4 cm SC Hollow-Core Slab + 0 cm SC Hollow-Core Slab + 5 cm Composite Slab

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needs to withstand a much lighter load than the concrete slab unless a finish of ceramic tiles is required on the wooden floor, which would increase the load considerably. And thus such a pre-dimensioned database would need to make a distinction between wood-framed floor systems with different finishes.

Translating such engineering variables (e.g. load) into architectural variable (e.g. finish) risks overloading a designing architect with a lot of choices. This would contradict the intention of providing easily accessible structural infor-mation.

Although a database was produced in this investigation that gives interest-ing information on the thickness of floors, it also shows that there are many decisions involved that guide structural design. These decisions are not only on the level of finish and its implication for the structure, but also on the di-rection of a span and its consequences on the rest of the design, the need for fire resistance and its possible implications for the structure, the possibility of integrating steel beams into a concrete floor plate to reduce its height, the combination of certain materials during construction, the insight to suspend a load from a structure above instead of resting it on a structure below, and so on. When I design a structure as an engineer, dimensioning is only one aspect that guides me in developing a structural concept; my field of knowledge and experience is much wider and more complex. It does not seem likely that software tools will be able to replace the multi-level expertise and creative abilities of a structural designer, which enable creative or innovative design.

Addis describes this human factor of structural design:

The model of a universal building built up by the human mind is far too subtle to feed into any computer, and the workings of this mental image are far too fast to see. An engineer simply knows, feels – the nature of the relationship between floor span and depth, between the shape of a struc-tural section and its deflection, between the rise of an arch and its stability and outward thrust. In a way which is half visual, half feeling, an engineer can imagine all the different consequences of changing column spacing, floor structure, a material, or the relative dimensions of members. The im-pression is of an imaginary object that is almost alive... Much of this type of engineering knowledge cannot be written down and cannot be learnt quickly; it has to be built up gradually and through direct personal experi-ence. (Addis 1994, p.16)

Therefore this effort to improve structural input in the architectural design process by providing the architect with structural software tools is abandoned.

An important part of creative structural design lies in the human factor of the

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103 engineer. Leaving out the structural designer in an architectural design process will likely limit the range of creative design possibilities.

Studies have also shown the importance of face-to-face meetings with co-designers and the use of sketching to solve problems in engineering design, while online databases and software are only beneficial to a limited percent-age of engineers as a source of ideas for design (cf. Chapter 2.3). It is likely that architectural design that takes into account structural design will similarly benefit from a collaboration between architect and structural engineer in face-to-face meetings and through the use of sketching. Therefore this doctoral in-vestigation will focus on such collaborations between architect and structural engineer as a team of creative design experts.