Kohler Ronan Consulting Engineers - KR Vision Newsletter - Issue 6, 2017

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VISION ISSUE SIX | 2017

Clash Detection: What to Know, What to Look for As technology continues to develop, more and more projects are switching from traditional 2D AutoCAD design to 3D BIM modeling such as Revit. BIM allows the design team to better coordinate construction and their design intent to ensure that costly change orders are minimized during construction. To this effect, one of the many benefits of BIM is the continued development of clash detection software not only within Revit, but also alternative programs such as Autodesk Navisworks. While it may be easy to depict ductwork, piping, and light fixtures within a ceiling cavity, construction tolerances always need to be considered. Modeling piping in a tightly-spaced group is not difficult, but can this piping be supported? Or insulated? While Revit allows both the design and construction teams the ability to review physical clashes between objects, it does not consider construction tolerances. However, Navisworks has been developed to provide a much higher level of review. In this article, we will work to better explain the importance of using Navisworks correctly. Improper use of this software can generate clash detection reports which are both impractical, unhelpful, and misleading to the design and construction teams. What Level of Development Is Used? Level of Development (LOD) can be described as the level of detail which has been incorporated into a model. Higher LODs ensure that a model is considering smaller elements whereas a lower LOD is primarily considering large elements only. Model elements with the highest LOD will be a field verified representation in terms of size, shape, location, quantity, and orientation. Models of this level are typically

part of the construction team coordination; lower LODs are used during design. How Should We Analyze Object Clashes? The Autodesk Navisworks Clash Detective tool allows its users to choose “Clash Rules” as well as tolerances. The tolerance can be defined as the distance between two objects that is permissible. Choosing proper Clash Rules allows the user to avoid highlighting conflicts that are intended, for example, two segments of ductwork which are physically connected. Similarly, using tolerances which are too broad will result in clashes between objects which are not actually in conflict; a tolerance of 6” will be too broad. On the other hand, a tolerance of 1/8" may be so narrow that it is physically impossible to construct. No matter what the tolerance or rules being applied, members of the design team must rely on their own industry knowledge and years of experience to allow adequate tolerances for construction. Is the Same Object Listed Twice? Three Times? More? If a user implements Clash Rules incorrectly within Navisworks, it is possible for the same clash to appear multiple times. For example, when a pipe is in conflict with a segment of ductwork, it may list conflicts such as Duct/Pipe, Duct Insulation/Pipe,

Pipe Insulation/Duct, and so on. This occurrence will inflate the overall quantity of clashes which are indicated, which in turn will make an accurate review more difficult and time consuming. In order to avoid this type of inflated clash reporting, it is critical to implement the correct Clash Detection Rules. Proper implementation is the only way to ensure the generation of truly valuable information for the design team (Duplicates Rule).

Figure 2: Pump vs. Connected Piping Conflict (Pumps should have piping connections.)

Should These Objects Be Connected? Having a basic understanding of MEP systems will give the reviewer the knowledge needed to identify elements that should and should not be connected. Should piping be connected to this object? What about ductwork? Air handling equipment, for example, will often have ductwork and piping connections. Without these continued on page 4

IN THIS ISSUE CFD in Auditoriums

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Maintaining Museum Environment 3 Revit® Corner 3 Figure 1: Instances of the Same Pipe vs. Duct Conflict

ALL TEXT ©2017 KOHLER RONAN, LLC

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