The Buildings, Floor Levels and Divisions
A basic rule is that all disciplines will use a modeling method wherein the model is split by floor level and all model elements belong to correct floor, even though modeling programs could support a different approach. There are many reasons for this: model based analyses are often done by floor, construction sites deal mainly with floors, and facility and property management also use floor divisions. This does not mean that the BIM should be divided into separate models or files by floor, only the components in the model are split and aligned to appropriate floors. From project to project it is possible to make exceptions to this requirement if needed.
Each separate building will be handed over as an independent model. If necessary, the building can be divided into multiple parts which will be agreed between the project team. Each building is normally handed over as a single model in the IFC and native formats. Building services systems are sometimes delivered as separate models for each floor and system. In very large buildings, architectural or even structural models sometimes have to be divided into separate models by floor.
The concept of a floor is slightly different between the different disciplines. This might be a bit confusing especially between the architectural and structural disciplines, since they deal with same elements. The following guidelines should be followed in modeling:
The differences in the modelling of the floor illustrates by the two images above; Architectural BIM on the left and Structural BIM on the right.
- In the Structural BIM, each floor contains the horizontal structures above and the vertical structures that support them. The basement floor slab together with the foundations belongs with is a separate floor, and the top floor of the model also includes roof structures. The structural BIM contains also those bulky surface structures that are essential for the load-bearing capacity of the structure such as fire insulations.
- In the Architectural BIM, each floor contains the floor slab and its surface structures as well as the suspended ceilings and bulky acoustical structures in the ceilings. The architect does not need to model the foundation, but the base structure should be modelled at least above the ground level. Roof and roof structures are modelled as a separate floor. The roof equipment and accessories are normally not modelled unless otherwise agreed on.
The qualifications, experience, and previous success in BIM coordination of the proposed BIM Manager and the Design Team should be considered when selecting architecture and engineering (AE) consultants.
The Design Team provides:
- A federated BIM model, fully-coordinated and assembled in a model checking software format. (eg. Navisworks, Solibri.)
- Separate copies of each technical discipline model in the original software authoring tool.
- A 2D plan set, derived from the assembled BIM model, for contract bidding.