BIM Design intent model
Building information modelling (BIM) is a very broad term that describes the process of creating and managing digital information about a built asset such as a building bridge, highway, tunnel and so on. Fundamentally, the purpose of BIM is to ensure that appropriate information is created in a suitable format at the right time so that better decisions can be made throughout the design, construction and operation of a built asset.
PAS 1192-2:2013 Specification for information management for the capital/delivery phase of construction projects using building information modelling (now replaced by BS EN ISO 19650) suggests that building information models might be described as 'project information models' (PIM) during the design and construction of a development, whilst during operation of the completed development they might be described as 'asset information models' (AIM).
During the design process, the initial version of the project information model developed by design suppliers might be described as the 'design intent model'. This should show, '…the architectural and engineering intentions of the design suppliers'.
In the early stages, it is likely to include massing diagrams or 2D symbols to represent generic elements of the design, with some critical elements developed in more detail. It should demonstrate early co-ordination of different aspects of the design and may (depending on the employer's information requirements) include:
- Aesthetic intent, architectural form and spatial arrangements.
- Outline structural and services designs.
- High-level simulation results (to determine whether the design is likely to comply with requirements).
- Outline site and landscape design.
- Outline specifications.
- Schedules and reports demonstrating compliance with the brief.
- Preliminary construction and phasing sequencing studies.
- General programme information.
- An elemental cost plan.
As the design progresses, the model will develop and the level of detail will increase, including, first, objects based on generic representations, and then specific objects with specifications and method statements attached along with information about space allocation for operation, access, maintenance, installation, replacement and so on.
Ultimately, as the contractor and their supply chain take over development of the model from designers, it may be described as a virtual construction model (VCM), containing all the information necessary to allow the objects in the model to be manufactured, installed or constructed.
PAS 1192-2 suggests that '…the arrangements for this transfer of ownership, including its timing, should be defined in the conditions of engagement or contracts between the employer and the suppliers.'
Once the model has been verified against what has actually been constructed, it should be handed over to the employer as an as-constructed asset information model (AIM). A point cloud or LiDAR survey may be carried out to confirm the completeness of the as-constructed model.