One of the holy grails of BIM is the ability to automatically check models against requirements. This will provide huge benefits in terms of both quality of design and efficiency of process. In this article Dr Stephen Hamil looks at some of the progress being made in this area.
To check requirements within a BIM process, two basic things are needed:
1. Computable requirements.
2. Designs built using standardised BIM objects.
For example, if a client requirement is “all objects must be classified using a Uniclass 2 Work Results code” then this may be automatically checked. If, however, there is a client requirement “there must be sufficient means for giving early warning of fire for persons in the building” then this requires human judgement and cannot be automatically checked.
If a requirement is that “a bedroom in a residential care home should not contain more than one bed (this includes double bed)”, the need for a common language becomes clear. To automatically check this requirement we need:
1. To know the type of building – Is this building a residential care home?
2. To know the type of space – Is this space a bedroom?
3. To know that all objects are classified correctly – In any spaces of type bedroom are there more than one object of type bed (and that single and double beds are allowed)?
This simple example demonstrates the need for a new level of rigour when it comes to modelling. This takes BIM far beyond the basic benefits of visualisation, drawing generation and clash detection. A further challenge is that quite often information must be passed from one software package to another. The importance of an interoperable data language (for example IFC), in combination with extended standardised property sets and an agreed classification system is vital.
Visual assistance at design time
Parametric objects may be developed that assist the designer. Examples of this in reality could be in the form of an indication of minimum periods of fire resistance to an architect (figure 1), or clearance or coverage regions to a service engineer (figures 2 and 3).
Fig 1 – Using colour coding to indicate minimum periods of fire resistance in a design
Fig 2 – Visually indicating the required clearance zone around a transformer
Fig 3 – Visually indicating the coverage volume of a heat detector
Automated checking of design
When issuing a design to a client or for regulatory approval, a number of requirements can be automatically checked. This can be performed either by the designer as a quality assurance aid or by the recipient of the design as a verification of aid. Examples of this could be automatically checking:
• All objects in the geometric model match all objects in the specification model (figure 4).
• All accessible washrooms have enough turning space for wheelchairs (figure 5).
• All heat detectors are specified to BS-EN 54-5 (figure 6).
• The content of a COBie dataset for continuity (figure 7).
Fig 4 – Automatic checking of specification against design model
Fig 5 – Automatic checking of accessible design
Fig 6 – Automatic checking of specification quality
Fig 7 – Automatic checking of COBie datasets
The examples outlined in this article make it clear that progress is being made; however, further support is required.
Client requirements and regulatory checks must be written in a way that they can be turned into computable rules. Without this, further automatic checking of designs will not be possible.
Part of the BIM Task Group Labs area that is helping define “Level-3-BIM” looks at classification and standardised objects. At NBS we have been working hard behind the scenes supporting this Government initiative with input into both the Uniclass 2 object classification tables and the standardised object templates. The example in figure 7 is also from the BIM Task Group Labs area and is the output from the AEC3 UK Ltd COBie Testing Tool. This tool automatically checks COBie datasets for compliance, continuity and completeness using colour indicators and tool tip text.
Where designers use standardised information structures and the Uniclass 2 object classification codes, then those working with the building information models that are produced can benefit from this consistency as follows:
• Contractors and clients will receive information in the same format on every project.
• Manufacturers can create BIM objects representing their real life construction products that are aligned to the generic standard object.
• Software vendors can continue to enhance their products to support standardisation. The entire project team can then benefit through more efficient and better quality design, construction and maintenance of buildings.
• NBS BIM