The difference between these working paradigms has been described as lonely BIM vs. social BIM by John Tocci of Tocci Building Corporation (www.tocci.com), which is a forward-thinking construction company with headquarters in Woburn, Massachusetts. Lonely BIM can also be referred to as the use of "isolated BIM techniques for targeted tasks," whereas social BIM is the underpinning for the goals set forth by organizations such as the National Institute for Building Sciences' (NIBS) buildingSMART Alliance (according to Penn State's BIM wiki at http://bim.wikispaces.com/BIM+Project+Execution+Planning+Project). The ability to support information exchanges, such as the facility life cycle helix concept shown in Figure 7.1, necessitates the proper use of 3D models and nongraphic data in a highly collaborative environment. Furthermore, the buildingSMART Alliance and the National BIM Standard (NBIMS) stress the need for platform-neutral, open interoperability between applications, not just within a program such as Revit.

Figure 7.1. BIM data exchanges according to NBIMS

Image: Allen Edgar

Once a project team decides to participate in social BIM—either through desire or the requirements of a client—they must decide how to deliver this information in a useful way to all constituents throughout the project life cycle. Whether your client requires it or not, you should develop a BIM execution plan to define the goals, exchanges, and results related to the use of BIM.

The buildingSMART Alliance (www.buildingsmartalliance.org)—in an effort sponsored by the Charles Pankow Foundation, The Construction Industry Institute, Penn State Office of Physical Plant, and the Partnership for Achieving Construction Excellence (PACE)—has created a BIM Execution Planning Guide and template BIM Execution Guide. You can find the two guides at the Penn State Computer Integrated Construction (CIC) website: www.engr.psu.edu/ae/cic/bimex.

One of the most critical parts of a BIM execution plan is the definition of the goals and uses of BIM. If you are just beginning your implementation of Revit, perhaps you are using it because it is the latest parametric program to enter the AEC industry, or perhaps you are attempting to increase your drafting productivity. Defining clear and concise reasons for implementing BIM on each project will help you define where to concentrate your modeling efforts. According to the buildingSMART Alliance, "a current challenge and opportunity faced by the early project planning team is to identify the most appropriate uses for Building Information Modeling on a project given the project characteristics, participants' goals and capabilities, and the desired risk allocations." A listing of the common uses of BIM along with potential value opportunities and required resources is also available on the Penn State CIC website.

According to the American Institute of Architects' (AIA) "Integrated Project Delivery: A Guide," a BIM execution plan "should define the scope of BIM implementation on the project, identify the process flow for BIM tasks, define the information exchanges between parties, and describe the required project and company infrastructure needed to support the implementation." To be clear, the development of such a plan does not imply the application of integrated project delivery (IPD). IPD is "a project delivery approach that integrates people, systems, business structures and practices into a process that collaboratively harnesses the talents and insights of all participants to optimize project results, increase value to the owner, reduce waste, and maximize efficiency through all phases of design, fabrication, and construction." For the purpose of this chapter, we will consider only the collaboration and coordination between members of a project design team, not the interactions with a client or contractor.

For additional reading on IPD, refer to these sources:

In the collaborative process of sharing information via linked models, the coordinated positioning of each model is of paramount importance. Agreement on a common coordinate system and origin must be included in every project's BIM execution plan to ensure accuracy. This section will help you develop a fundamental understanding of the coordinate systems within Revit so you can configure and manage them in your projects. For a more complete history of coordinate systems and various examples of using them within Revit, we recommend the following class material from Autodesk University 2009, available at www.au.autodesk.com:

There are two coordinate systems in a Revit project: project internal and shared. Each system has essential features and limitations.

When you attempt to synchronize shared coordinates between linked projects, there are two tools to achieve this: Acquire Coordinates and Publish Coordinates. A simple way to understand the difference between these tools is to think of them in terms of pulling versus pushing:

It is important to understand the situations where you would pull or push coordinates between linked files. A typical workflow for establishing a synchronized shared coordinate system on a single building project would be as follows:

Acquiring Coordinates from a CAD File

A common scenario in a project workflow begins with the architect commencing a design model and receiving a 2D survey file in DWG format from a civil engineer. The survey is drawn in coordinates that are geospatially correct but may not be orthogonal to true north. The architect should create the model close to the internal project origin; however, the architect will need to ensure the building and survey coordinates are synchronized for properly oriented CAD exports and for coordination with additional linked Revit models from engineers in later phases of the project.

The architect will link the 2D CAD file into the Revit model but will first manually place it—moving and rotating the CAD file to be in proper alignment with the building model. Once the link is in place and constrained (or locked), the architect will acquire the coordinates from the DWG survey by switching to the Manage tab and from the Project Location panel, selecting Coordinates

For a campus-style project in which you might be creating multiple instances of a linked building model, you would most likely use Publish Coordinates to push information from a site model into the linked building model. Here's how that would work in a hypothetical scenario:

In prior versions of Revit, locating the project origin or shared coordinate point was only accomplished by using an imported AutoCAD file or by using spot coordinates and moving elements as required. Revit now provides two objects to identify these points: the project base point and the survey point. In the default templates, these points are visible in the floor plan named Site; however, they can also be displayed in any other plan view by opening the Visibility/Graphics Overrides dialog box, selecting the Model Categories tab and expanding the Site category as shown in Figure 7.8.

Figure 7.8. Project base point and survey point are found under Site in Visibility/Graphics Overrides.

To further expand your understanding of these points and what happens when they are modified, we have created a sample file for your reference. Open the file c07-Shared-Points.rvt from this book's companion web page (www.sybex.com/go/masteringrevit2011). In this file you will find three copies of the floor plan Level 1. Each is configured to display the project coordinates, the shared coordinates and a combination of the two. There are also two types of spot coordinates—one indicating project coordinates in which the values are prefixed with the letter p; the other indicates shared coordinates with the prefix of s. You can open these three floor plans and tile the windows (View tab, Window panel, Tile or type the keyboard shortcut WT) to get a better sense of how these points affect each other (Figure 7.10).

Figure 7.10. Tiled windows to examine the affect of project and shared coordinates.

Within this sample file, you can explore the effects of moving the project base point and survey point on your model's coordinates. When selected, the project base point and survey point have paperclip icons that determine the behavior of the points when you move them. Clicking the paperclip icon changes the state from clipped to unclipped and back to clipped.

Following is a list of the possible point modifications and explanations of how they affect the project. Note that in most cases you shouldn't have to move the survey point or project base point if you are using a linked civil file (2D or 3D) and acquiring the coordinates from the linked file.

Project Base Point (PBP): Clipped

Moving a clipped PBP is the same as using Relocate Project. That is, the model elements maintain their relationship to the PBP, but the relationship of the PBP to the survey point is changed.

Project Base Point: Unclipped

Unclipping the PBP essentially detaches it from the internal project origin. Moving the unclipped PBP is really only used to affect the values reported in spot coordinates set to the Project origin base. It does not have any effect on exported files.

Survey Point (SP): Clipped

The clipped survey point represents the origin of the shared coordinate system. Moving it is the equivalent of setting a new origin point. Use caution if you must move the shared coordinates origin if linked models already exist in which the shared coordinates have already been synchronized. In such a case, each linked model must be opened and manually reconciled with the model in which the origin has changed.

Survey Point: Unclipped

Moving an unclipped survey point essentially doesn't do anything. It doesn't affect spot coordinates and it doesn't affect the origin of exported files.

Linked Revit models utilize what we will call a portability setting that is similar to the way XREFs are handled in AutoCAD. Although this setting is not exposed when you initially link a Revit model, you can modify the setting by switching to the Insert tab and selecting Manage Links. Change the setting in the Reference Type column as desired (Figure 7.11).

Figure 7.11. Determining the Reference Type of linked Revit models

If you are utilizing linked Revit models where one or more of the project files have worksharing enabled, there are a few guidelines to follow as well as tangible benefits to be reaped. Be sure to read more about worksharing in Chapter 6, "Understanding Worksharing."

The first guideline is to ensure that the files received from consultants are set up as central files within your own domain. Even though you may not have direct access to your consultants' servers, Revit will attempt to reconcile the location of each project model's central file location. We recommend opening each received Revit file and using the following steps to set up a copy as a central file:

Figure 7.14. Relinquish all user-created worksets when saving a file that has been detached from central.

When the host model is enabled for worksharing, we recommend you create and reserve a workset for each linked Revit model, such as Link-RVT-Structure or Link-RVT-HVAC. This simple step will allow your team members to choose whether they would like any, all, or none of the linked models to be loaded when working on a host model. To enable this functionality, use the Specify setting in the drop-down options next to the Open button.

When the Worksets dialog box appears, select the worksets reserved for the linked models and set their Open/Closed status as you desire. The benefit of using worksets to manage linked Revit models is the flexibility it offers a project team. When a workset containing a linked model is closed, the linked model is unloaded only for that person—it does not unload for the entire team.

Additional flexibility can be leveraged through the use of the Workset parameter in both Instance and Type Properties of a linked model. In a large and complex project that consists of multiple wings where some of the wings are identical, each wing may consist of multiple linked models: architecture, structure, and MEP. Figure 7.15 shows a simplified representation of such a design where Wings A, D, and E are identical as are Wings B, C, and F.

Figure 7.15. Schematic representation of a complex project assembled with multiple linked models

In Figure 7.15, there are two Revit models for each discipline that represent wing design 01 and 02 (Arch01, Arch02, and so on). Note there are three instances of each linked model. For each instance of a linked model, the Workset parameter can be specified where the workset instance property represents the wing and the type property reflects either the entire discipline or one of the discipline models. For example:

Using this example, you can choose to open the Wing A workset, which would load all the discipline models, but only for Wing A. Or, you could choose to open the Link-Architecture workset, which would load only the architectural models, but for all the wings. Note that the workset Type Properties can be modified only after a linked model has been placed in your project. Access this setting by selecting an instance of a linked model and opening the Properties Palette, and then click Edit Type. Although this functionality can offer a variety of benefits to your project team, it should be used with care and proper planning as it can adversely affect model visibility if you are using worksets for visibility manipulation.

Worksharing-enabled linked models also afford you the flexibility to adjust the visibility of project elements for the entire project, without relying on individual settings per view or maintenance of view templates. For example, grids and levels are not usually displayed from linked models because their extents are not editable in the host model and the graphics may not match those in the host model. Without worksets, the owner of the host model would have to establish visibility settings for the linked model within all views and hopefully manage those settings in view templates. Assuming the owner of the linked model maintains the levels and grids on an agreed workset such as Shared Levels and Grids, you will be able to close that workset in one place, thus affecting the entire host project. To modify the workset options for linked Revit models, follow these steps:

To summarize using linked Revit models, let's review some of the benefits and limitations. You should carefully consider these aspects not only when preparing for interdisciplinary coordination, but also when managing large complex projects with linked files.

The following list highlights some of the benefits:

The following list highlights some of the limitations:

Note that the structural model is essentially a blank project with a few element types specifically built for this chapter's lessons.

Once you have linked one or more Revit files into your source project file, you may want to adjust the visibility of elements within the linked files. By default, the display settings in the Visibility/Graphics dialog box are set to By Host View for linked files, which means model objects in the linked files will adopt the same appearance as the host file. In the following exercise, we'll show you how to customize these settings to turn the furniture off in the linked file and then display the room tags.

You should observe that all the furniture and casework from the linked architecture file are no longer visible in the Level 1 floor plan. It is important to mention that in a typical architecture to structure collaboration scenario, the Structural Engineer is likely to have a view template in which typical architectural elements are already hidden. In such a case, the default By Host View settings would be sufficient. The previous exercise illustrates a scenario where additional visual control is required.

While the previous exercise focused on the display of model elements, a slightly different approach is required to utilize annotation elements from a linked file. In the following exercise, we will show you how to display the room tags from the linked architectural model. Note that many other tags can be applied to linked model elements in Revit 2011 products.

After completing these steps, you should see the room tags from the linked architectural file in the host file. Remember that you can tag other model elements in linked files. Try using the Tag By Category tool to place some door tags on the linked architectural model.

With the project file saved from the previous exercise, switch to the Collaborate tab and select Copy/Monitor

Figure 7.18. Element tabs available for Copy/Monitor in Revit Architecture

As shown in Figure 7.18, the Copy/Monitor Options dialog box in Revit Architecture is divided into five tabs representing the elements available to be copied and/or monitored. For each element tab, there is a list called Categories And Types To Copy. As shown in Figure 7.19, the Floors tab lists the available floor types in the linked model in the left column and host model floor types in the right column. Notice that any of the linked types can be specified with the option Don't Copy This Type. This can be used for quality control if your project's BIM execution plan states that certain elements are not to be copied. For example, if walls are not to be copied, switch to the Walls tab and set all linked wall types to Don't Copy This Type.

Figure 7.19. The Copy/Monitor Options dialog box allows customization for intelligent collaboration.

At the bottom of the Copy/Monitor Options dialog box, you will find a section called Additional Copy Parameters for each element tab (Figure 7.20). Note that the additional parameters are different for each element category. For example, when levels are copied and monitored, an offset and naming prefix can be applied to accommodate the difference between the finish floor level in a linked architectural model and the top of steel level in the host structural model.

Figure 7.20. Additional copy parameters can be applied to each element category.

Let's take a closer look at each of the element category options available for the Copy/Monitor tool:

Continue with the project file saved in the previous exercise in this chapter. In this exercise, you will do the following:

These steps will establish the intelligent bonds between elements in the host file with the related elements in the linked model. With the file c07-1-Structure.rvt open (saved from the previous exercise), activate the South elevation view.

If you now select any of the grids or levels in the host file, you will see a monitor icon near the center of the element. This indicates that the intelligent bond has been created between the host and the linked element and will evaluate any modifications in the linked file whenever the file is reloaded.

Save and close the file c07-1-Structure.rvt and then open the file c07-2-Architecture.rvt. Using the procedures you have learned earlier in this chapter, link the structural file into the architectural model. Placement should be done in the Level 1 floor plan using Auto – By Shared Coordinates positioning.

Use the Copy/Monitor tools in Monitor mode to establish the relationships of the grids between host and linked models. This will ensure that changes to grids in either model will be coordinated.

When a linked model is reloaded, which will happen automatically when the host model is opened or by manually reloading the linked model in the Manage Links dialog box, monitored elements will check for any inconsistencies. If any are found, you will see a warning message that a linked instance needs coordination review.

The coordination review warning is triggered when any of the following scenarios occur:

To perform a coordination review, switch to the Collaborate tab and select Coordination Review

Figure 7.21. The Coordination Review dialog box lists inconsistencies in monitored elements.

For each of the changes detected in Coordination Review, one of the following actions can be applied. Note that actions resulting in changes to elements will only be applied to the host model; they do not modify elements in a linked model. Also note that not all options are available for all monitored elements.

As you can see, Coordination Review can be a powerful tool to support the collaboration process. Remember that such a tool may not be appropriate for all elements at all times. For example, instead of copying and monitoring columns and grids, it may be sufficient to copy and monitor only grids, as the columns placed in your host model will move with the grids anyway.

In this exercise, you will utilize two files that have already been linked together with monitored elements between both files. You can download the files c07-Review-Arch.rvt (architectural model) and c07-Review-Stru.rvt (structural model) from this book's companion website: www.sybex.com/go/masteringrevit2011. In this exercise, you will do the following:

Remember that you can't have a host model and a linked model open in the same session of Revit. To make this lesson easier, you can launch a second session of Revit. Open c07-Review-Arch.rvt in one session and c07-Review-Stru.rvt in the other.

In the previous exercise, you might have noticed the appearance of a monitored floor sketch. Why did a floor sketch change if you only moved a grid and renamed another? The answer lies in constraints and relationships. The exterior wall in the architectural model was constrained to be 2"-0" offset from grid line F. When it was moved, the exterior wall was moved to maintain the offset. The sketches of the model's floor slabs were created using the Pick Walls tools, creating an intelligent relationship to the wall. The modified grid affected the wall, which modified the floor, and the Coordination Monitor tools ensured that all changes were detected and presented to you for action.

The Interference Check tool in Revit is a basic tool supporting 3D coordination. You can use it within a single Revit project model or between linked models. You can also select elements prior to running the tool in order to detect clashes within a limited set of geometry instead of the entire project.

For more powerful clash detection capabilities, Autodesk offers Navisworks Manage (www.autodesk.com/navisworks), which is a multiformat model reviewing tool with various modules supporting phasing simulation, visualization, and clash detection. Figure 7.23 shows an example of a model in Navisworks Manage comprised of Revit, Tekla Structures, and AutoCAD MEP. Some of the benefits of using Navisworks for interference checking over Revit include automated views of each clash, grouping of related clashes, enhanced reporting, clash resolution tracking, and markup capabilities. Although many other 3D model formats can be opened directly in Navisworks, Revit models can be exported directly to Navisworks format with an exporter add-in.

Figure 7.23. 3D coordination model in Navisworks Manage

Figure 7.25. Results of an interference check are displayed in the Interference Report window.

Note that you can navigate in the 3D view using any method (mouse, ViewCube, or Steering Wheel) while keeping the Interference Report open. This facilitates resolution of the clashing items. The results of the interference check can also be exported to an HTML format report. Simply click the Export button and specify a location for the report. You can now share this report with other members of your design team for remedial actions on linked models.