CADENCE AEC Tech News #105 (September 18, 2003)

17 Sep, 2003 By: Lachmi Khemlani

In This Issue: BIM Solutions: Bentley Architecture--Part 2

  • Schematic Design
  • Detailed 3D Modeling and 2D Documentation
  • Conclusions
  • Relevant Links

This is the second of the two-part series of the AEC Tech News that explores some critical features of Bentley Architecture--formerly known as Architecture for MicroStation Triforma--from a BIM (Building Information Modeling) perspective. In the last issue (, we saw the key aspects of Bentley's approach to BIM and how these have been translated into its architecture-specific BIM application, Bentley Architecture. I also described in detail a key new feature in Version 8.1, the 2D/3D Choice, which gives the user not just the traditional choice between 2D and 3D but four different 2D/3D design modes that help smooth the transition from 2D to 3D.

This issue looks at the capabilities of Bentley Architecture for schematic design, detailed 3D modeling, and 2D documentation. Other BIM-related aspects of Bentley Architecture, such as lighting, rendering, animations, schedules, reporting, and so on, are beyond the scope of this two-part series. I will, however, return to them in future issues.

Schematic Design

One critical omission in the repertoire of most BIM solutions is a set of dedicated tools for programming, space planning, conceptual sketching, and quick 3D massing, which can allow building information developed at the early stage to be intelligently reused in the subsequent design development phase (see my recent review of another leading BIM solution, ArchiCAD, at

Bentley Architecture has tools for tackling some conceptual design tasks, but on a piecemeal basis; it lacks a comprehensive and integrated solution for schematic design that ties into detailed design. There are no tools for space programming, except the ability to import Excel spreadsheets and place them in the drawing window. The programming data in such a spreadsheet cannot be directly linked with the spaces that are created, which would have been useful. Similarly, there are no sketching capabilities. You can, however, import a sketch (say, of the site) and use it as an underlay for developing 3D models.

There is a toolset for creating and labeling spaces that can be used for space planning, but it has very limited functionality. Spaces can be drawn or created within walls by a new flood method, and a label can be placed displaying the space name, area, and a few other attributes. The area display in the label updates automatically if the enclosing walls are moved. However, spaces cannot be converted into walls, which would have been a useful automated step going from space planning to detailed design. Space labels are not one composite entity and are also not tied to the spaces; thus, moving or deleting a space does not move or delete its associated label. Spaces cannot be filled with color, a critical requirement of the space-planning task.

Bentley Architecture has the full gamut of solid and surface modeling capabilities--the advantage that comes from being built on top of MicroStation TriForma. However, these are more suited to developing detailed 3D models; they lack the intuitiveness and ease of use needed for quick 3D massing found in dedicated conceptual design tools such as SketchUp and Autodesk Architectural Studio. Also, Bentley Architecture does not have the ability to automatically derive the building shell--complete with semantically intelligent wall, floor, and roof objects--from a schematic design massing model. This means the effort spent in developing a massing model cannot be effectively directed towards jumpstarting the detailed design process.

A separate application, Bentley Facilities, is available for facilities management, and it has the ability to create, label, and color-code spaces. However, a facilities management software is a limited substitute for an effective schematic design solution that needs to integrate programming, space planning, conceptual sketching, and quick 3D massing tasks.

Detailed 3D Modeling and 2D Documentation

A key strength of Bentley Architecture as a BIM application lies in the actual detailed modeling of the building. It has an extended toolset for different building components such as walls, doors, windows, columns, roofs, floors, stairs, and so on. The Walls toolset, for instance, comprises 11 different tools for different functions: placing walls, and placing and building wall assemblies; breaking, joining, and connecting walls; modifying wall geometry and wall type; cleaning up wall intersections and managing automatic wall unification in the 2D extracted drawing; making cuts in walls and creating wall pockets and recessed utility areas to accommodate other building design elements.

When any building element is modeled, default settings are used for its type information, which can be changed later when required. This allows the designer to focus on the design and its modeling, without being burdened by specifying type information until necessary. It also keeps tool dialogs concise and easy to navigate. Type specifications follow industry standards, with higher-level categories called families containing several individual element types called parts.

Common relationships between building elements are automatically inferred, which makes it easier to create and edit the building model. Thus, moving a wall segment with the Move Form tool automatically stretches the adjoining walls to maintain connectivity. If you want to move an object without maintaining its relationships with other objects, that option is also conveniently available--you just need to deselect the Imply Relationships box in the Move Form dialog that automatically opens up when the tool is used. This automatic inferencing ability, however, is restricted to disciplinary relationships only, which means that only architectural elements such as doors, windows, furniture, and other fixtures can be moved with walls. To create a relationship between structural elements such as beams and columns with walls, you have to group them, making the association a geometric rather than a semantic one. Columns and beams created in Bentley Architecture do not even move in relation to each other. Such automatic inference relationships between structural elements are created in Bentley Structural only. Cross-disciplinary collaboration could be significantly enhanced if the appropriate inference relationships are automatically made between the architectural, structural, and HVAC elements created by the different Bentley building applications.

2D documentation in the form of plans, sections, and elevations can be derived from a detailed 3D building model in Bentley Architecture as extracted, two-dimensional section cuts, created with a Drawing Extraction Manager utility. The entire range of MicroStation dimensioning and annotation tools are available to detail out the drawings (see my review of MicroStation V8 at Because the drawings are extracted, rather than being views of the same building model (as in the case of BIM solutions based on the single building model concept), any change in the 3D model requires the drawings to be recalculated for the changes to be updated.

Because the 3D model and 2D drawings in Bentley Architecture are independent entities rather than views of the same building model, it is also missing a Project Browser-like interface found in the single model-based BIM applications, which lists all the plans, sections, elevations, 3D views, details, schedules, and so on, and lets you conveniently switch between them.

The federated, decentralized approach, however, is also what gives Bentley Architecture its main edge over single model-based competitors--the ability to handle projects of any complexity. A building project would typically be represented by a 3D master model, comprised of several master models for architecture, structure, HVAC, and other discipline-specific areas. A disciplinary master model such as the architectural one created in Bentley Architecture would also usually be made of multiple smaller models that can be completed by several project teams working simultaneously. The smaller models would be references to the master model. An unlimited number of references can be attached to a file; these references can have attached references of their own. There is no limit to the depth of this reference hierarchy, and this is what enables the application to model very large projects just as easily as smaller ones.


As a BIM application, Bentley Architecture is particularly strong on the detailed building modeling front. The evolutionary approach it embodies has both advantages and disadvantages. On the plus side, it includes a solid and extensive repertoire of CAD and BIM features that have been improved over years of development. Its innovative 2D/3D Choice approach will appeal to those who want to transition gradually from CAD to BIM. On the downside, it also inherits the problems of CAD applications, notably their complexity.

The lack of adequate support for conceptual design processes such as space programming, planning, and quick massing is a critical omission that all BIM solutions, including Bentley Architecture, need to address. Otherwise, BIM implementation will run into the same problem that has dogged CAD all this while--early stage design processes will continue to be done manually and will not be digitally recorded and meaningfully reused in the subsequent design workflow.

Relevant Links

Bentley Architecture:

Bentley Structural:

Bentley HVAC:

Bentley's BIM Web site: