On the makings of bim
Today’s plethora of bim products poses some exciting questions and challenges
Long before everyone had iPads, in fact, before we even had writing or language, humans expressed themselves through drawing. From pre-history cave sketches to modern-day, ultra-precise, computer-aided design systems, mankind has used drawings to communicate design intent and shape the very world around us.
Since eminent designer draughtsmen like Leonardo da Vinci in the 14th century, we have toiled to standardise the presentation of these ideas through symbolic 2D conventions of plan, section and elevation, while improving accuracy and increasing design complexity. We have imagined and built amazing things with pen and paper; now computer and plotter. So why should the development of our design tools stop here?
Prior to computers, architects were, of course, equipped with drawing boards, pen and paper. Traditional manual draughting meant edits were time-consuming, there was an increased risk of error, and creating artistic, detailed documents required a great deal of skill and training. The introduction of 2D cad software in the late seventies and early eighties rendered the manual documentation of this phase obsolete. The same process and symbology was replicated in the software and was easier to edit and faster to draw. Cad systems such as Autocad, MicroStation and Vectorworks (formerly minicad) became mainstays of the architectural profession, replacing the drawing board and digitising the documentation stage of the design process.
There was a short blip in this migration to 2D cad for architects and it occurred here in the UK in the late seventies. A number of universities had focused on geometry and cad research, namely Cambridge, Oxford and Bristol, with their graduates producing home-grown and revolutionary design systems.
Four in particular – Really Universal Computer Aided Production System (RUCAPS), General Design System (GDS) Sonata and Acropolis – went beyond mere replication of the 2D process, by providing 3D modelling capability for architects.
The basic concept involved creating a 3D model of a building and from that central model, extracting the geometry to generate sections, elevations and plans. These very expensive and limited systems were championed by the large London practices and can be seen as the forerunners of today’s bim systems. Unfortunately, the cost, lack of processing power and the complexity of these early design systems meant they were replaced with cheap desktop 2D cad systems. They were without doubt ahead of their time.
2D to bim
While the building market moved back to the old 2D drawing methodology, other industries such as aerospace, automotive and process plant design persevered with 3D modelling systems. These industries built intelligent 3D virtual designs in their cad tools, which could be analysed, simulated, optimised and directly manufactured from.
With increasing power available on the desktop, and the reducing cost of software, the last 10 years have seen 3D modelling become standard in engineering design. Bim represents exactly the same “virtual design” methodology but for the building industry. And just to be clear, bim is not one company’s product but an approach to design, with solutions available from Autodesk (Revit), Bentley (MicroStation Architecture), Graphisoft (Archicad) and Nemetschek (AllPlan).
Is the architect expected to pay for bim’s front loading of the design process?
While 2D cad merely digitised the dumb drawing board process, bim models combine all the elements of a building; walls, doors, windows, slabs, roof components, structural steel, mechanical elements, water and electrical piping in 3D. Each element can be fully specified, so each knows its relevant properties (height, width, material, cost, etc.) enabling the extraction of fabrication and quantities data later on in the design process. By creating an information-rich model, architects can also make informed decisions from exploring the virtual form and volumes, together with using analysis tools to explore lighting, shadowing, airflow, solar-heat gain, energy usage and total carbon footprint before it is built.
Bim models can also be used to generate computer-rendered images or animations for presentation and planning. As projects are held in a single model, any changes that are made to the model automatically update the plans, sections and elevations that are generated. The model could also be used for structural steel analysis, HVAC modelling, clash detection, quantity take-off and scheduling. If used correctly, bim promises many benefits: coordinated documentation, reduction in time, fewer errors on site, and the potential for a reduction in total project wastage.
While in principle, the bim concept makes perfect sense, moving to a bim solution does involve investment and changes in both employee skill-sets and project workflow. Those using traditional 2D cad methodologies need to plan a transition to using any bim product carefully. There is no turnkey solution.
Apart from the internal cultural issues always present when embracing change, there are also external cultural influences. For instance, using a shared centralised model in a project with other firms opens questions on standards and requires new contractual/ legal agreements should problems arise. Bim models “front load” more work into the design phase and benefits all downstream building disciplines – is the architect to pay for this? New models for collaboration, risk and reward are required.
Technically, models have a tendency to get big fast (many tens of Gb for multi-storey buildings) and require powerful workstations, servers and network infrastructure. Also, while the current batch of bim tools are all fairly good at rectilinear buildings, the more interesting organic forms can present modelling challenges. While bim tools automatically output plans, sections and elevations there is a very good chance that the style will not be to any company standard. While there is some internal flexibility, some firms resort to editing these in a 2D cad system, thus losing the automated output benefits. There are also issues with data exchange between competing bim systems, as these models are proprietary databases, not files.
There are recognisable benefits to adopting bim methodology and moving to 3D. A number of key firms that have made the leap, such as Laing, Aedas, Ryder and HOK, are now seeing a return on their investment. The key question is how to survive the process?
?Martyn Day is editor of AEC Magazine, a bi-monthly journal for construction professionals. www.aecmag.com