Building Information Modelling (BIM)

BIM - A new approach to construction

Industry participants have yet to agree on a common definition of BIM, and use BIM to refer both to an approach to construction and to software tools that may be used during the construction process. BIM may also refer to the act of creating a building information model or to the model itself (i.e. a structural dataset capturing all of the necessary information for a building that has been created by a BIM software tool). BIM processes, goals and concepts are also sometimes referred to as Virtual Design and Construction, Virtual Building Environment and Virtual Building and Integrated Practice.

Historically, the original focus of CAD software solutions was to represent 2D geometry via graphical elements. However, more complex information, such as the relationships between graphical elements, could not be added. The next generation of CAD, 3D CAD programmes, initially focused on creating geometry in support of visualisation of structures, and subsequent advances concentrated on creating realistic rendering and light effects. More recently, object-oriented CAD systems replaced 2D symbols with building elements or objects, capable of representing the characteristics of common building elements. These building elements can be displayed in multiple views, and non-graphic attributes can be assigned to them, thus enabling such elements or objects to become intelligent. This combination of parametric 3D geometry with assigned rules and dimensions allows the representation of complex geometric and functional relationships between building elements. Parametric objects are defined as parameters with relationships to other objects, allowing such objects to automatically re-build themselves based on the rules embedded in them (for example, if a window is defined as being wholly within a wall, and if the wall is moved by the designer, the window automatically moves with the wall).

BIM was initially conceived as the latest generation of object-oriented CAD systems, in which all of the intelligent building objects that combine to constitute the design of a structure can co-exist in a single virtual structure that captures everything known about the structure. The use of BIM as the latest generation of CAD systems is sufficiently developed that, for example, the US General Services Administration now requires delivery of spatial programme information from BIM for major projects.

The construction industry demands a product beyond the existing capabilities of the CAD driven BIM solutions. The progressive trend is towards a greater degree of process coverage that can be effectively captured in a solution that uses a 5D building model.