Principles of Dividing BIM Models into Volumes

Introduction

This paper highlights both the concepts and the precautions that should be considered during the plan of BIM projects workflows. Also, it describes the decomposition of BIM models into 3D spaces in order to provide better management of BIM models and utilize the most benefit of it. Specific considerations are varied according to the models’ stages and usages, whether the models are for design, construction or facility use. These stages are well classified in Royal Institute of British Architects (RIBA) plan of work 2021. Brainstorming and testing of various models’ decomposition plans are essential prior to start of the modelling works to avoid unforeseen obstacles and works risks that might be happen especially during the development of the graphical and non-graphical data inside the BIM models.

Mechanisms of Splitting BIM Models into Volumes

A typical volume strategy as shown in figure 1 might be changed from one project to another however, there are strategic concepts and principles that affect the decision plan of decomposing the models into 3D spaces which should be at early stage. This is essential to keep a smooth work flow and better collaboration between the task teams.

Figure 1: Typical Models Volume Strategy

The following concepts will illustrate different strategies of model’s splitting taking into consideration that some of these methods are based on my practical experience and other methods will be incited as follow.

  • Splitting Models by Procurement Volumes

This method of model’s splitting is based on the scope of each sliced volume. Each volume has an owner who can be another contractor or subcontractor based on the type of procurement.

This approach was actually followed in one of the mega projects implemented in Egypt and it was defined from day one both the ownership and the scope of each 3D space.

  • Splitting Models by Space Volumes

This method is very useful especially in large projects that have large built-up areas. It specifies a separate volume for each specific space such and each space volume includes its disciplines such as the combination of Structure model, Architecture model, Mechanical model and Electrical model which are related to the mechanical shaft in a certain building.

  • Splitting Models by Area Type Volumes

In some projects for example in hotels or malls as illustrated here in figure 2, the BIM models can be subdivided to 3D spaces in accordance with the type of space. Regarding hotels, we might have model volume for the hotel public areas and another model volume for the hotel guest rooms and another model volume for the hotel MEP rooms and so on. In malls, as illustrated here in figure 1, the models are spliced into interior model for walls and doors, core model for circulation elements, parking and prayer toilet model, shell model and skylight model (Kish, 2019). 

  • Splitting Models by Functional Volumes

In some cases, it might be planned to split the model by discipline for the sake of analysis and calculations such as the case in structure analysis models or hydraulic analysis models.

Another example is in the Architecture discipline, the 3D spaces related to the circulation elements such a stair or to the Architecture elevations such as facades, its relevant models can be sliced into separate volumes.

  • Splitting Models by Structural Joints

The Structure design restrictions provide certain limitations for the continuity of the structure skeleton as a one piece. Thus, it becomes logic to split the models into 3D spaces at the locations of structural joints such as expansion joints or settlement joints.

  • Splitting Models by Level of Information

Reference to the model development stage, the level of information is a key factor in the mechanism of models splitting. At some time, the limitation of hardware capabilities makes it difficult to support one model especially when the models are in the higher levels of development and have huge details.

Precautions of Subdividing BIM Models into Volumes

Several precautions shall be considered while planning of splitting BIM models into volumes (3D spaces) starting from the adoption of company strategy for model management and how to ensure that model data remains coordinated, well structured and efficient. Also, effective management is required to control the efficiency of models, reducing of errors and improving of its consistency between the task’s teams. Thus, the following points have to be checked on deciding the strategy of number models volumes and the components inside each of it (Ismail, 2017).

  1. BIM model file size should allow best refresh and interactive responses.
  2. Quantifying approach and method of measurements should be considered while subdividing models into volumes
  3. Number of subdivided models should not be organized and be controlled to avoid excessive number of models that might lead to several links and attached links.
  4. The ownership of each model should be defined.
  5. The models volumes shall ensure the concurrency of engineering activities. Hence, once the models’ volumes are defined and agreed within the building, each individual discipline can produce their design model or construction model without reference to other as long as the resultant solution remains within the agreed volume.

Conclusion

In conclusion, volume strategy is one of the key points that shall be well defined at early stage and shall be documented in the Task information Delivery plan and Master Information Delivery plan. Also, keeping a solid plan of models’ volumes enables all the systems from different disciplines to have unique 3D space for each area in the model, this helps a lot in avoiding of overlapping or duplication in model’s 3D spaces. As well, subdividing large projects into volumes enables keeping them manageable and minimize risk of low productivities result from models’ corruption (Grimston, 2019).

References

Brian, K. (2019). Stepping Up to Completing Extra Large Projects in Revit – Part 1 [online].  Available from: https://archsmarter.com/large-projects-in-revit-1/ [accessed 17 November 2021].

Grimston, P. (2019) Strategies for dealing with large projects in Autodesk Revit [online]. Available from: https://www.symetri.co.uk/insights/blog/strategies-for-dealing-with-large-projects-in-autodesk-revit [accessed on 16 November 2021].

Ismail, I. (2017). 101 Revit Tips, 101 Best Practice Tips for Revit Model Management [online].Available from: https://issuu.com/iuidesign/docs/101_revit_tips-iftikhar_ismail [accessed 14 November 2021].

Law, M. (2019). Understanding BIM Project Requirements [online]. Available from: https://www.augi.com/articles/detail/understanding-bim-project-requirements [accessed 14 November]

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