Identifying & Resolving Issues using Navisworks

Identifying & Resolving Issues using Navisworks


In any large multidisciplinary project, the task of reviewing the composite design requires a mix of applying subjective judgment as well as standard tests and analysis to identify conflicts between the elements incorporated from the models integrated.

The use of BIM models has revolutionized the way integrated project models are reviewed. By objectively merging elements from all models, it ensures that all members of the design team are seeing and understanding the same design. The ability of computers to automatically verify the spatial relationship between various model elements allows clash detection tools to easily find conflicts between complex systems, eliminating the need for project members to spend countless hours over light tables manually searching for clashes with each model revision.

{slider Reviewing and Marking Up the Composite Model |closed}

Autodesk® Navisworks® software provides four essential tools for reviewing and capturing feedback on the composite model. These tools enable you to:

  • Measure and verify the placement and clearance between model elements.
  • Redline to highlight and annotate potential problems and issues found during review.
  • Tag and classify issues for follow up.
  • Comment and capture textual descriptions of the issues for later review.

As issues are found and tagged, it is helpful to classify and organize them for later retrieval and follow up. This can be done with folders and careful naming of the saved viewpoints to help team members can quickly sort out and find issues that pertain to their tasks. {slider Performing Clash Detection}

Clash detection enables the effective identification, inspection, and reporting of interferences in the composite project model. It helps reduce the risk of human error and oversights during model reviews by automatically detecting model interferences. Clash detection can be used as a one-time sanity check for completed design work or as part of an ongoing project audit and quality control process.

Navisworks® Manage software’s Clash Detective tool enables teams to conduct clash tests between model elements by checking across the entire composite model or by checking specific subsets of the model elements. Clash checking can look for these types of conflicts:

  • Hard—conflicts of elements in 3D space (If such a conflict is temporal in that it occurs for only a certain phase of project, it is termed a “soft” clash).
  • Clearance—instances of not meeting set clearances between pairs of objects.
  • Duplicates—identical instances of the same geometry.

It is important to recognize that not all clashes are truly problems. In fact, some clashes may have been intentional during the modeling process for the sake of simplifying the modeling task. Clash results need to be judged in the context of the level of detail included in each model, and this need underscores the importance of having an experienced model manager with a strong foundation of construction and design experience.

Teams can create batches of clash tests to be repeated with each model revision, and these batches can be exported and shared. Teams can also create a custom clash test suite for reuse on multiple projects. This approach provides an easy way to roll out a standardized set of tests across an organization that enables the expertise of sophisticated model users to be reused by everyone.

Clash tests can also be used as a way of implementing object intelligence. For example, a custom clash test could be created to check for compliance with a local building codes based on object information and the properties defined in a particular model system.

{slider Creating Digital Requests for Information}

Issues that require resolution are typically documented, communicated, and tracked as requests for information (RFIs).

With Navisworks® Manage, RFIs can easily be created using the results of the clash detection process. These results can be saved as viewpoints with associated tags and reviewer comments, and then shared as fully formatted reports that contain both an image and the description of the problem.

Clash detection can be overwhelming if not approached in a systematic way. Defining clash tests too broadly can yield an enormous number of clashes, so experience and judgment are required to define meaningful test. By carefully defining selection and search sets of model elements, the accuracy and effectiveness of the process can be greatly improved.

When clash results contain multiple clashes deriving from a single design issue, reviewers can organize the clashes into folders and subfolders to simplify reporting and tracking. After organizing and classifying the issues, images can be annotated and reports prepared with comments that synthesize the problems and communicate them effectively to the designers who must resolve them.


Learning Objectives

After completing this lesson, you will be able to:

  • Understand the importance of creating viewpoints that include markups, comments, and measurements.
  • Organize viewpoints into meaningful hierarchies that support an effective workflow for resolving the issues.
  • Assess the validity of the clashes reported and understand the importance of properly constraining a clash detection test.
  • Appreciate the value of performing systematic clash detection, using a combination of user-defined tests and custom clash tests commonly employed within an organization.
  • Investigate clash test results and organize them into an effective format for reporting them to the responsible disciplines for resolution.


Reviewing and Marking Up

In this exercise, you will learn how to:

  • Create viewpoints that effectively communicate issues needing resolution.
  • Measure, tag, redline, and add comments to a saved viewpoint.
  • Manage issues through searching comments and tags based on issue status or author.

Figure 5.2.1 - Saving viewpoints that highlight a lighting issue

Video Tutorial
Student Exercise
  • Open the downloaded .NWF file in Navisworks Manage.
  • Create viewpoints to effectively communicate the following problems found during model review:
    • Conference Glass Door Panel Missing on Level 2.
      • Create this view using a top cutting section plane that reveals the Level 2 interior spaces, and then hide the Structural Model and the Ceiling objects to better expose the view of the door panel. (The difference is subtle, but the fixed panel in the model is missing the door handle.)
    • Level 2 Sink Fixture at Wrong Elevation.
      • Create this view by using a front face cutting section plane to expose the restroom layout in a perspective-elevation view.
    • Missing Atrium Railing on Level 3.
      • Create this view by walking through the model or using a face cutting section plane from back to front.
  • Classify these viewpoints and organize them into file folders that target the disciplines responsible for resolving each issue.
  • Try searching for comments created by particular authors or having different status.

Figure 5.2.2 - A viewpoint displaying the restroom sink located at wrong height

Performing Clash Detection

In this exercise, you will learn how to:

  • Design clash detection tests to look for conflicts between different pairings of element types using the selection tree and set manager.
  • Specify different types of class detection tests to look for hard, clearance, and duplicate clash types.
  • Use batch tests to evaluate and verify design iterations.
  • Save and export clash tests for use on other projects.

Figure 5.2.3 - Clash detection results between the wood framing and HVAC systems

Video Tutorial
Student Exercise
  • Open the downloaded .NWF file in Navisworks Manage.
  • Run a hard clash test looking for conflicts between the HVAC elements and concrete beams on Level 1. Use the selection tree to select the model elements to be verified.
  • Repeat the same hard clash test as above, but use a selection set select the concrete framing elements.
  • Run a clearance clash test with a tolerance of 6" (0.15 m) to look for conflicts between the ducts and lighting fixtures on Level 1.
  • View the results from the previous test by selecting each of the reported clashes and altering the display settings for each viewpoint to highlight the conflict.

Figure 5.2.4 -  Concrete beams interfering with the round flex duct of the HVAC system

Creating Digital Requests for Information

In this exercise, you will learn how to:

  • Explore the results of the clash tests as lists and as scene views.
  • Manage and organize clash test results by the cause of the problem or the discipline responsible for resolving the problem.
  • Differentiate between valid and invalid clashes.
  • Tune the appearance of the viewpoints in order to highlight the essential elements shown.
  • Creating clash reports using various output formats options (Viewpoints, HTML, TEXT, or XML).

Figure 5.2.5 - Grouping like clashes into clash sets

Video Tutorial
Student Exercise
  • Open the downloaded file in Navisworks Manage.
  • Review the clash test results and the conflicts reported between the concrete framing and the exposed HVAC system in the ceiling space of Level 1. Then create folders to group and consolidate the clashes related to the Flex Duct Round and to the Oval Duct.
  • Using a similar approach, group and consolidate the clashes reported in the clearance clash test between the ducts and lighting fixtures on Level 1. Group the clashes results into folders based on the root causes of the conflicts.
  • Add tags and comments to each set of clash results that describe the needed resolution.
  • Create a Viewpoint report and an HTML to report these results to the responsible disciplines. Open each report to confirm the accuracy of the simplified set of clashes included in the reports.

Figure 5.2.6 -  Managing clashes from concrete framing and exposed ducts


Reviewing and Marking Up

  • Who are some of the different audiences for whom we might want to focus our markups to the saved viewpoints?

Examples include owners, HVAC consultants, plumbing consultants, structural designers, and fire protection specialists.

  • For each of those different audiences, describe the types of viewpoints that would focus on their primary concerns.

For owners, views of project architectural features, both external and internal.

For HVAC consultants, views that show the interaction with the plumbing and electrical systems, and views of rooftops or utility rooms where equipment is typically located.

For plumbing consultants, views of the sanitary system, wall cross-sections, and views that show the interaction with HVAC and electrical systems.

For structural designers, views that show the interaction with the HVAC and plumbing systems.

Performing Clash Detection

  • Describe examples of standardized clash detection tests that might be saved and repeated across many projects.

Examples include sprinklers against HVAC ducts, HVAC ducts against structural framing, plumbing piping against HVAC ducts, or structural framing.

  • Should each discipline be responsible for clash testing its own model before contributing it to the model aggregator for cross-discipline testing?

Yes! Intra-model clashes, conflicts, and inconsistencies should be eliminated (or understood) before checking for conflicts with models created by other disciplines.

  • What are the key advantages of automated clash detection of BIM models when compared to the traditional method of comparing paper documents?

Dramatically faster to perform and free of human error. Also, without the need for large light tables or being in a design office, project managers can perform clash testing at the construction site.

Creating Digital Requests for Information

  • What is the best format to use to distribute punch lists or digital RFIs to the relevant parties?

One of the best formats for reporting viewpoints and issues is the HTML report option. This format can easily be used to reach a wide audience, as the reports require no additional software to see the screenshot of the tagged item and any associated comments.

  • Is it wise to save all the review session markups over the course of the project and the model’s versions?

It is always safer to document the work, whether for internal referencing or for contract management. You can easily store each version’s review’s session tags in folders marked with their date, thus keeping records of what you have found and discussed. You can then save this to go back to it later and easily distribute it to other team members.

  • How can this paperless workflow for reviewing issues save costs over the life of a project?

Using digital RFIs saves time in the printing, distribution, and administration of the information requests. The 3D visualization environment minimizes the need to interpret and compose written explanations of each issue, since the interactive model carries so much contextual and particular information implicitly. A 3D model is worth more than 1,000 words!

Key Terms

Key Term
Redline Tag
A common method for marking up a viewpoint to report a potential issue. Adding redline tags automates viewpoint creation and provides a method for reviewers to comment freely on the model.
Hard Clash
A clash defined by two objects actually intersecting.
Clearance Clash
A clash type occurring when two objects come within a specified distance of each other. Selecting this clash type also detects any hard clashes.
Duplicate Clash
A clash type characterized by two objects that are identical in type and position. This type of clash testing may be used to clash an entire model against itself to detect of any items that may have duplicated by mistake.