Australian LOD BIM

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As part of the BIM presence in Australia for a long time and the continuous development of the methodology for 20 years, it is worth citing an important document of the Australian BIM Standard of 2013 in the context of the current ISO 19650 standard. ISO LOD and NATSPEC approach BIM Paper NBP 001 (Building information and level of development) [2] is convergent, therefore I am quoting its most important fragments:

The format of many LOD tables obscures rather than clarifies important patterns and relationships, making them less effective for the intended use. While many LOD table templates are available, there is currently no industry-accepted standard. Practitioners are confronted with different LOD table formats from design to design, making them difficult to interpret; When documented in a table, the LOD can serve the following purposes: o As a common reference for stakeholders planning to develop the model. o To register contracts for model products. o To plan and coordinate project resources. o To communicate project requirements to team members and organize their workflow. o To monitor the progress of the project program implementation. LOD is a means to an end. The LOD level is meaningless without a clear definition of the model's purpose or intended uses. The resources devoted to the development and maintenance of the LOD Tables should be proportionate to the extent to which they support project management; AIA LOD notations consist of numbers at intervals of 100, which gives system users the flexibility to define intermediate LOD levels. Defining additional LODs can be crucial in some circumstances, especially for contractual reasons, e.g. handing over models from design team to construction team. Definitions of each LOD from LOD 100 - LOD 500, as given in the AIA Working Document G202 - 2012,

Figure 1: Level of development versus level of detail

The following scenarios also show how LOD can be used to convey the development expectations of the chair in Figure 1 at different stages of a hypothetical design, and to what extent this may be independent of the graphical level of detail.

LOD 100: The photorealistic image of the chair is selected for rendering purposes only. Even if detailed information is associated with it, it is not assumed to be relevant at this stage.

LOD 200: The general model of the chair is selected for the layout of the furniture, although the decision for the actual chair has not yet been made. The important thing is the nominal size of the surface it represents.

LOD 300: During documentation, a simple placeholder is selected to help minimize model file sizes. The chair may appear in schedules or be used for quotation, but is not expected to be used for ordering.

LOD 400: A chair with a specific manufacturer and model number is selected for the purpose of the order.

LOD 500: The chair has the manufacturer, model number, supplier, serial number and date of purchase, but its image, eg a photo, does not necessarily have to be included in the model.

Document citing

An integral part of the LOD concept is model development (sometimes referred to as progress) and collaboration. With so many model elements having to develop over time by different parties, how can this process be coordinated? AIA Draft Document G202 - 2012 Building Information Modeling Protocol The form contains a model item table to document collaborative model development during a project using protocols defined in related AIA Draft Document E203 - 2012 Building Information Modeling and Digital Data Exhibit and AIA Draft Document G201 - 2012 Project Digital data protocol form. A model element table can be used to document who is to be the model element author (MEA) for each model element in each phase of the project, and to what level of detail it needs to be developed. The purpose of LODs is to provide clarity and certainty about what is expected of all involved so that they can plan their work with confidence. Knowing the LOD of the model's elements at each stage will allow you to determine how much the recipient will rely on it, how much effort will be invested in solving problems related to it, and how much responsibility will be taken for the work based on it.

The error in applying a level of detail to the overall model is understandable as the models and drawings common to each phase of a project are often used to illustrate the concept. Freehand sketches are used to illustrate the conceptual design phase, sketchy plans for the initial or schematic design phase, and working drawings during the construction phase. The apparent uniformity of the drawings is masked by the fact that many elements are at different levels of development in terms of decision making. To further confuse, it is common for the development of a model to move in tandem with graphic and non-graphic information - as you define more precisely the form of an element, harder, more detailed information about the element is often added. But this is not always the case - this assumption is wrong.

The intended use of a model directly influences the way it is modeled and the data it contains. As with any product, it is important that potential users of the model have a good understanding of its intended use and any restrictions associated with its use. A model with a high proportion of high-level detection elements does not necessarily mean that it is well designed for any application. The LOD values ​​shown in the LOD table are only relevant for the documented uses and for those relying on them for a given milestone. If the recipient of the model is unaware of its purpose or assumes that it can be used in a way that was never intended, significant problems can arise.

RECOMMENDATIONS FOR LOD IMPLEMENTATION: A key recommendation of this article is to use existing LOD standards; Trying to develop a new standard from scratch during the project should be avoided. Detailed recommendations:

1. Define the geometry of each model element for each nominated level of detail with reference to the standard.

2. Define the data content of each model element for each nominated level of detail by reference to the standard, eg NATSPEC BIM Object Element Matrix (BOEM)

3. Use a standard LOD table to document the LOD of individual model elements over the agreed time, preferably based on a spreadsheet,

4. Use standard protocols to be followed by team members when jointly managing the development of the model in the project,

Coordination and LOD Proper coordination of building elements is obviously a key part of the design and construction process. One of the significant advantages of 3D modeling is the ability to identify collisions or collisions between building elements during the design process, so that they can be resolved before construction begins. Avoiding the need to resolve these issues on site can result in significant time and cost savings. There is no point in starting detailed clash detection early in the design stages as so many elements are loosely defined and subject to constant change - a lot of effort would be wasted. On the other hand, it is important to identify potentially significant coordination issues as early as possible so that they can be remedied. Large clashes in a well-advanced project are always more problematic and time-consuming to solve. If the level of detail and coordination are parallel model development issues, how do you link the two and how do you determine the appropriate degree of coordination required in the different steps? A measure of coordination similar to that for LOD and how they relate would be useful.

BIMForum LOD Specification: The BIMForum Development Level (LOD) specification is a reference that defines and illustrates the characteristics of multiple model elements at different LOD levels. Clear definitions allow the authors of the models to define what their models can rely on, and the downstream users to clearly understand the usefulness and limitations of the resulting models. The purpose of the Specification is to help clarify the LOD structure and standardize its application so that it becomes more useful as a communication tool.

PRINCIPLES FOR CREATING A PLANNING MODEL: Use the following model element development ordering rules to create and interpret LOD tables: The wider, overarching aspects of the design must be resolved before attention is shifted to the more detailed aspects. The overall size, layout and form of a building must be well defined before proceeding with the design of the structure and structural system. The placement of fixtures, fittings and fixtures in interior spaces must be defined before detailed planning of services etc. Identify and rank building elements in terms of their impact on other elements, especially those for which other people are responsible. disciplines or model element authors (MEA). For example, relocating an electrical outlet and associated wiring is less problematic than rerouting the main air supply riser. Therefore, a higher LOD level would be assigned to the air supply riser earlier in the design than the power outlets. Distinguish between items that have more restrictions on their placement, and those that have less. For example, sewer pipes must be laid so that they can fall down to the risers without interruption - smaller gas and water pipes can be laid with much more freedom. So, in the context of project development, it makes more sense to focus on the layout of the sewage system in front of the layout of the supply pipes. Likewise, large passages in a structure must be located and properly dimensioned in front of smaller ones. Accordingly, embedded, embedded, or recessed model elements connected to services should be assigned a higher LOD earlier in the design phase than surface mounted or loose elements not connected to services. Highlight items that are shared between authors of model items or for which responsibilities transfer from one side to the other. You may need to define team protocols in more detail for these items. Identify the systems and components designed by the contractor (design and construct). The LOD of these elements in the given project stages will be determined by the contractual expectations, eg D&C mechanical services based on schematic design, D&C based solely on performance criteria (no schematic). The development of information related to the model is just as important as Geometry development should be planned with care and discipline to maximize the benefits of BIM. Evaluate the information needed to deliver the results specified for each project phase, and create a plan for adding and managing this information at the model element level.

LOD TABLE DEVELOPMENT STRATEGIES: Documenting design requirements in a LOD table represents a major investment for the team. The following strategies for this process are general guidelines: Adapt the LOD table to the needs of your project. A simple project, or one where the design team has worked together many times before, will not require the LOD Table to be as detailed as a complex project involving teams that have not previously worked together and are less confident of what to expect from them . different. Match the LOD development to the project program. Attempting to rewrite model development to the nth degree at the very beginning of a project can prove futile and a waste of effort, especially before all team members are involved. LOD tables should at any time reflect the reasonable goals set by experienced practitioners. They must be routinely reviewed and updated as required by the project. Continuing from the last point, it is best to develop the LOD table gradually. As with the design itself, it is better to start by developing the LOD tables at a broad level where anyone can agree and gradually refine them as required. Rather than getting bogged down in detail right from the start, it's more productive to agree on sensible milestones in model development and then explain what each side needs to do to achieve them. Invest only as much energy as is needed to develop a LOD table to enable project stakeholders to plan and budget with confidence. Consciously avoid tinkering with it when the benefits cannot be clearly identified.

Sources:

[1] pixabay.com

[2] NATSPEC BIM Paper NBP 001 BIM and LOD - Building Information Modeling and Level of Development First edition 2013 Publisher: Construction Information Systems Limited ABN 20 117 574 606 https://www.google.com/url?q=https%3A%2F%2Fbim.natspec.org%2Fimages%2FNATSPEC_Documents%2FNATSPEC_BIM_LOD_Paper_131115.pdf&sa=D&sntz=1&usg=AFQjQnfQZE_wyl4CNfQZE_wyl8CNfQZE