Archibus Smart Client Extension for Revit
As-Built and Lifecycle BIM Models
One of the key information flow decisions revolves around the graphical BIM models themselves and the as-built geometry. The following sections describe several methods for managing the information flow and content of your graphics.
Maintain the As-Built Model
In this method, the facility department maintains its data in a view of the construction as- builts, or the facility department submits redmarks to the architect, who maintains the model through ongoing changes -- such as merging or splitting rooms.
This is usually the methodology imagined by most BIM practitioners, but it has certain limitations. The facility managers need to perform a large number of updates, manipulations and queries on graphics data, and doing so on the full construction model is often slow, as the construction models tend to be large. Revit users carefully plan their "Save to Central" operations for this reason.
The methodology also has ownership consequences as decisions made from the as-builts have liability consequences, and updates made with the proper care for construction consequences are expensive. Some organizations reject this approach as not reflecting the division of duties between the professions.
Use a Separate Lifecycle Model
In this method, the facility managers create a separate lifecycle model from the construction as-builts. The facility managers remove detail that is useful for construction but not necessary for day-to-day management and maintain their own changes (for example, merging rooms). For more detailed information, see Preparing the Revit Model for Facility Management.
When it comes time for a major renovation, the architect compares the lifecycle model against the as-built model to determine which portions of the building should be field-surveyed before designing the renovation.
The valuable dependencies within a design model and within a lifecycle model are different. For a design model, the ability to move a structural wall and have all floors of the building reflect the change automatically is essential. As such, design models tend to be as large as the computing infrastructure allows. However, once the building is built, moving a support wall is rarely an option. For this reason, lifecycle models tend to be only as large as is practicable for planning, with an emphasis on quick load time. You can use one model to hold a group of floors or one model to hold an individual floor.
That said, you may wish to take care to make certain that you use common reference coordinates for you separate models. This is so that if you have a particular analysis that you need to perform -- such as lining up chases to review an upgrade to your building systems -- you can pull the separate models together for that analysis.
Use AutoCAD Drawings
While the notion is somewhat anathema to BIM purists, you can profitably use AutoCAD drawings to maintain your space data, as you can quickly export accurate CAD drawings for each level from Revit. See Exporting to DWG Format.
Sites may prefer AutoCAD for several reasons. They may use interns, contractors, or offshore providers that do not have Revit skills but that are comfortable with AutoCAD. Depending on how accurately the underlying walls, columns, and exterior walls are tagged, a site may need to re-draw the space boundaries in any case, and that task is arguably as fast in AutoCAD as it is in Revit.
Before embarking on this direction, however, sites may wish to consider several factors. "BIM" aside, 3D models will be the de facto standard for graphics data for new construction. Facilities are as easy or easier to draw in Revit as they are in AutoCAD, even if you have no existing plans to start from. Few new architectural graduates know AutoCAD; all of them know the newer 3D tools.
Finally, when you are using Archibus, there is no problem with keeping your existing facility drawings in AutoCAD and adding new buildings in Revit format. Archibus records the database data the same way, searches across the graphics data consistently, and publishes both AutoCAD and Revit data to the Web and the enterprise using a consistent format. The choice of one or the other is always one of practicality, not of necessity.