The structural engineer has greater impact on a building’s sustainability than is first apparent. There are four important questions in terms of building sustainability:
- what and where to build?
- how to build?
- whether or not to build?
In order to answer these questions, choices have to be made from a wide range of parameters. The advantages of one choice may have a negative impact on another parameter, and short-term advantages may be detrimental to a long-term vision. This is why a holistic approach is of vital importance, and results in an integrated design through close collaboration between the various parties (client, architect, engineering offices, etc.).
what and where to build?
The questions of what and where to build are above all determined by social, economic and demographic considerations, and thus the designers have a somewhat minor impact on these. As structural engineers, we can of course play a supporting role in answering these questions. Take for instance the need to build on brownfields, due to a lack of space.
how to build?
It is on the question of how to build that the structural engineer has the greatest impact. Important issues here are the building materials and the building process. In relation to building materials, a structural engineer paying attention to sustainable building aims:
- to calculate as thoroughly as possible so that the minimum sections and quantities are achieved depending on the programme of requirements and loads resulting from this
- where possible, to use recycled or recyclable materials
- to propose materials from sustainable sources (e.g. for concrete, this entails a limit on the Portland cement content)
This is of course achieved from a holistic approach, so that the impact of the choices proposed can be viewed more broadly than the structure and the construction phase themselves.
A sustainable vision on the building process encompasses, among other things, attention to waste management and restricting nuisance in the neighbourhood:
- in relation to waste management, the structural engineer may examine the possibilities of reusing the demolition materials on the site itself (as sub-foundation, for instance), or to have them sorted so that they can be more easily recycled or reused elsewhere.
- nuisance in the neighbourhood can be limited by, for example, choosing prefab as far as possible so that activities on site become shorter, vibration-free foundation systems, etc.
Besides the abovementioned domains on which the structural engineer has an impact, he or she also plays a supporting role toward other designers in the area of energy efficiency (concrete core activation, solar panels, etc.), daylight penetration (sections of load-bearing façade), acoustics (wall composition, acoustic mass), etc.
whether or not to build?
Although it is not always clear from the outset, in many cases it may be advantageous – and not only in the field of sustainability – to examine the possibilities of renovating an existing building, or parts of this. The structural engineer plays a major role in this, and he or she must give sufficient attention to investigating the existing structures and plans in order to arrive at a well-founded recommendation concerning the possible reuse value of the existing building.
Subsequently to this, together with the architect the structural engineer will attempt to design the structure of a new construction in such a way that it is sufficiently flexible to be used in the future for any other purposes. However, this flexible design should not lead to an excessive use of materials, since otherwise possible, indefinite long-term benefits are negated by the definite, extra material use.
If a new construction cannot be entirely reused in the future, the structural engineer at the least strives to make reusing elements as straightforward as possible. This can be achieved, among other things, by avoiding ‘wet’, on-site cast connections, in other words by making the structure as easy to disassemble as possible, and by drawing up a sufficiently detailed file (including stability sheet with all assumptions, loads, … a clear as-built file). The market for second-hand building elements such as beams and columns is at present very restricted, yet nothing rules out this changing in the future (such as through pressure from the government, material shortages, …).