BIM management plans are generally clear on this subject (at least in Quebec): the phases as well as the phase filters of the different Revit files of the same project should match . But why?
At first glance, newly introduced stakeholders to the context of BIM projects might believe that this request from BIM managers is futile, but on the contrary: the phases are clearly used to meet the requirements of a project that needs to be realized in several stages. These also impact the deliverables, as well as the coordination processes (for the sake of this article, we are assuming that we are sequencing the project without segmenting the project for a phased construction delivery, which is a completely different subject). For these reasons, it is essential that all project stakeholders share the same interpretation of the different phases of a project.
Demystifying Revit phases
Revit phases have been a core feature of the software since its earliest days. Their use is widespread but often misunderstood. The basic principle is simple:
The phases essentially represent a sequence of realization in a project, from the past to the future. However, it’s important to understand that the phasing needs of various professionals are likely not the same. For example, architects can require many more phases to manage the construction stages than mechanical engineers who arrive later in the process, often at the very last stage of construction. This is not problematic, as long as the interpretation of the sequence remains the same for everyone.
The phases will be used to specify the stage of creation and demolition of the different objects of a project, as well as to control the different views of the project (plans, elevations, 3D, etc).
Demolition is often misunderstood as a construction phase. The reason is understandable: it is an important step in a project. The principle of status of objects is also intuitive, but very powerful once mastered:
Under the phase filters, there are four column titles that represent the possible statuses for objects at a specific phase. The status "Demolished" represents the state of an object whose creation phase is prior to the phase of the active view, and the demolition phase the same as that of the active view. This clearly shows that it is not required (nor desirable!) to create a phase in Revit only for demolition.
In addition, it is important to note that some issues still exist when using this phase management technique. For example, creating a demolition plan that demonstrates existing parts can be more time consuming because you will need to use alternative techniques such as superimposing views or copying rooms. Make sure you understand the advantages and disadvantages of each technique, and if in doubt, do not hesitate to consult an expert!
Linked files and phase assignment
When creating a Revit link, one of the first steps is to assign each phase from the linked model a corresponding phase from the active model. This allows Revit to match the project steps between the different models. In the example mentioned earlier, the mechanical engineer might require fewer phases than the architect. You will still, however, have to match the names of the phases for equivalent steps between projects.
Synchronisation of phase filters
Once the Revit phases are correctly assigned to the linked models, why is it still necessary to match the names of the phase filters between the different models? It’s important to understand that when linking Revit models to each other (like when creating a federated model), phase filters in the active model will not be used. On the contrary, Revit will try to find the equivalent phase filter in the Revit link to control the display of different objects. If the filter does not exist in the link, the filter "Show All" will be used by default.
For example, a BIM manager who has created a federated model for QA purposes might want to isolate in a view the elements created in Phase 1 of the project by applying a "Show New" filter to a view identified in Phase 1:
However, if the linked models do not contain the "Show New" filter, all objects will be displayed in the view, including the existing ones! It is therefore critical to agree on a phase filter naming convention at the very beginning of the project to avoid this kind of situation.
To conclude, it is important to understand that phase management methodologies have not only an impact on our own model, but also on those of all other project stakeholders. Some disciplines such as MEP are even more impacted by the use of Revit phases, due to the inherent complexity of demolishing existing systems and reconnecting equipment to new systems ...
The good BIM management practices stipulated in the project's BMP are there for a good reason!
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