By Emma Kent
I recently wrote a blog piece about re-purposing existing buildings to bring them up to date and maximise their value to the occupant. The flip side of that discussion is ensuring that when we design a new building, we make the most of the opportunity to engineer it for future flexibility. A blank sheet of paper for an innovative building design is the perfect chance to think about future-proofing.
Future-proofing can mean lots of things in different contexts such as resilience to future climate change, the ability to overlay ever-changing technological advances and the ongoing need to reduce our demands on our overstretched environment. In the context of this blog, I am thinking about the future structural adaptation of a building to facilitate refurbishment, modification or change of use.
This is a balancing act between cost and environmental impact now, and adaptability later. For example, we are designing a new office building but the client wants to be flexible regarding to whom she lets the space. She might want to offer spaces as dance studios or classrooms instead of offices. The design imposed loading for an office is 2.5kN/m2. But the design imposed loading for a dance studio is 5kN/m2 or a classroom it is 3kN/m2. So, there would be a significant uplift in the required size of all the building elements (slabs, beams, columns and foundations) if we were to truly design in this flexibility of future use. The higher the loading, the bigger and stronger the building that is required to support it. That is without even considering the vibration design criteria of the dance floor (perhaps a subject for another blog…!). This increased loading would have a knock-on increase to the cost, programme and embodied carbon of these elements, which may be prohibitive. The additional load capacity might never be used, if the building were kept as offices. The same principle applies if we arbitrarily design for long spans to increase column-free area which might never be required.
So, are there any practical measures that engineering designers can take to assist their future selves, which might reduce designing-in of wasteful redundancy which may never be required?
Good record-keeping will assist tomorrow’s designer to understand the design criteria for which the asset was originally intended. For example, detailed records of ground conditions, loading criteria, deflection criteria, material properties and section sizes could be kept in the operation and maintenance manuals for a building. You would be amazed at how many operation and maintenance manuals contain the cleaning requirements for every sink on the project, but fail to record the length of the piles used, or the number of bolts at each connection.
BIM is also a key tool in record-keeping about a building and designing for creative re-use. A BIM model can be the repository for many of the records mentioned above. BIM could (should?) be a live information source, with the model updated to reflect changes to the building or replacement components installed. The future engineer should be able to pick up a BIM model and immediately get an up-to-date picture of the state of a building and its original (or new) element sizes and their properties. This should be the goal – but often once the final drawings for a project have been issued, the facilities maintenance team rarely update the record information with changes that they or others make. But we all need a goal to work towards!
Record-keeping should be supplemented by labelling of materials and components on site. Currently stamping of steel components is permitted but this practice is not compulsory and stamps may not contain all the information required for re-use (for example steel grade, age and section type). Components could be labelled in a permanent way for example using embedded or permanently fixed ID tags. RFID (radio frequency ID) technology is increasingly being used to track and trace tools and components across building sites but this could also be used for full life-cycle asset tagging to drive the capture and re-use of existing elements. We could cast-in passive RFID tags into precast concrete elements to identify their attributes in the future. The advent of the internet of things (IoT), combined with RFID tagging, might allow us to directly identify the properties of construction components, totally bypassing information recorded by BIM. We might even be able to have passive construction components feeding back and reacting to real world events autonomously via the IoT, without the need for human intervention.
Minor changes can make a significant difference when considering creative re-use. For example, specifying and using bolted connections rather than welded connections can allow a frame to be deconstructed and modified or re-used with minimal impact. Making the spacing between secondary beams sufficient to fit an intertenancy staircase between them can make life a lot easier for a client. Considering the floor to floor heights carefully with adaptation in mind is also a sensible idea.
I also think that emerging technologies will make a significant difference as to how we design buildings to be more flexible. One such technology is adaptive structures. Adaptive structures are capable of counteracting applied loads actively by means of sensors, control intelligence and actuators. The structures we design now are purely passive, meaning they are designed to meet all the loads applied under all circumstances without external input. At some point, we could be using this passive capacity for everyday loading, whilst using additional active control to deal with dynamic situations such as earthquakes or storms. You can read more about the research into this on the UCL website.
Designing for future flexibility is all about making decisions, with the client, early in the design process and then ensuring both decisions and designs are clearly communicated and recorded. Think of it as doing yourself a favour now, for ten or twenty years’ time!
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Image: © Nor Gal