What is BIM (Building Information Modeling)? It is a technology for creating digital models of buildings with relevant information about each component, so that, throughout every phase of construction, this information can be extracted, combined and analysed to support planning, execution, financial and logistics decisions and operations in an integrated, organised way.
Many people confuse BIM technology with BIM software: the first is the concept and the process; the second is just the set of tools used to apply it. In other words, there is no point modelling a project in BIM software without adding the relevant construction information to it.
Another important aspect of BIM is the joint, collaborative and simultaneous work of all the disciplines involved in the project, based on single or integrated models of every discipline. This saves time and increases productivity and the accuracy of decisions, which are based on realistic virtual simulations.
Features of the BIM process
Parametrisation
This is the addition of information to the model, or BIM database, in a predefined way common to all elements. There are many possible parameters, such as the object code, the floor or housing unit of a building element, and the date of execution or creation. These parameters should be defined in the BIM execution plan and serve as minimum guidelines for everyone involved in the project.
Communication
Just as the parties involved in the process need to communicate constantly, so do their tools, through smart models that move between the tools of each discipline. That is why the IFC format was created: the international language of BIM files. It allows different tools to communicate, so everyone involved in construction can work on the same project without depending on a single piece of software. This is also known as openBIM, a synonym for interoperability between software. Therefore, to be considered BIM, any software must import and export model information in IFC-compatible files.
Level of development (LOD)
LOD stands for level of development of the BIM project. It defines how detailed each project phase is:
- LOD 100: a model with geometry, lines, symbols and volumes only, such as a massing or volumetric study.
- LOD 200: approximate quantities, size, shape, location and orientation are added, along with geometric information attached to model elements.
- LOD 300: all geometry and element properties match the real conditions of the development. This is when the schematic design has been approved and the construction documents are developed, up to design coordination.
- LOD 350: details and elements showing the interaction with other designs, dimensions and technical notes are included.
- LOD 400: details of how a given element should be built or assembled are added. In Brazil, projects rarely reach this level of detail.
- LOD 500: corresponds to how the development was actually built, the as-built.
Dimensions
BIM is not just a 3D representation of a project. It can add different dimensions, depending on each development:
- 3D: three-dimensional modelling with technical information, dimensions and position in space, allowing inconsistencies to be checked with clash detection tools and material lists to be extracted.
- 4D: scheduling. The time parameter is added, so the progress of construction can be followed virtually.
- 5D: cost. Elements are linked to cost parameters. With an organised model, this data can be synchronised with a construction cost database, keeping the budget always up to date.
- 6D: comfort. Thermal, energy and lighting simulations of the building.
- 7D: operation after completion. Maintenance, warranty and operation parameters.
- 8D: health and safety. Forecasting possible risks during construction.
In Brazil, it is most common to work up to 5D, covering design, scheduling and cost. But the need for 6D simulations is growing, to meet the building performance standard.
Design coordination
In BIM, communication happens at every level, including between the models involved in a project, to check spatial clashes and incompatibilities between disciplines, or between schedules and cash flow. Checking spatial clashes is called clash detection: an automated check, carried out by specific software, of inconsistencies between elements of the 3D model. It allows check sequences to be set up between disciplines and filters to be applied to detect only clashes between specific elements. For example, when checking plumbing against architecture, there is no point analysing clashes between walls, pipes and fittings, but it is useful to check whether pipes conflict with doors and windows.
When checking and resolving clashes, solving problems in one discipline often creates new ones in another. That is why, to avoid rework and ensure coordination, it is important to follow a hierarchy of checks, so that problems already solved do not come back.
BIM execution plan
Like an internal manual specific to each project, the BIM execution plan (BEP) is the document that defines the schedule, the minimum parameters of each object, the level of development of each stage (LOD), naming conventions, reference points and much more. In other words, all the guidelines of the BIM process in the company, the project or the stage.
BIM in practice: the Independência building
The Independência residential building, in Belém, was designed in BIM by the studio and presented in the 2023 BIM Yearbook of Santa Catarina. The pages are shown below. See also our building projects.
