Monday, September 27, 2010

Organizing BIM Content by how it is used

Implementing the Component: Primary, Secondary, and Tertiary

Components which are added to an architectural model can be categorized as primary, secondary, and tertiary. Exactly which category a specific component fits into depends largely on the individual or discipline. In addition to the architectural components, a series of structural, mechanical and specialty components are used to further detail the model for design and analysis through specialty consultants and contractors. For architectural purposes, it is not always necessary to add each structural element, mechanical equipment, or specialty components unrelated to the design intent. In many cases taking into consideration only basic dimensions and locations is acceptable to allow other contractors and consultants to design based on the spaces allotted. While this is a disjointed approach and in no way collaborative, it is not an uncommon practice, and as such should be taken into consideration when thinking about how to organize the various types of components used in modeling.

Primary components are made up of the core elements used to enclose and access spaces; floors, walls, ceilings, roofs, and openings. These elements of the project are the first to be added, often during schematic design. They divide spaces, create layouts, and enclose the overall building. Walls are added into a project and used to enclose and divide spaces. It is important to maintain a consistent reference point within the wall so that they align properly. Because walls have several materials within them, from structural, to surfaces, to finishes, and determining the reference point is often specific to the needs or type of project at hand. When creating exterior walls, using the exterior edge of the structural member as the reference plane may prove to be the most effective, where when creating interior walls, the center line of the wall may be most effective. Using a consistent strategy for aligning walls minimizes the risk of errors through design development. In many cases the number of layers and thickness of materials within the wall is unknown until well after the original walls have been placed. A great deal of time is spent manipulating these elements such that they may become permanent as design development progresses. Once the design begins to consider secondary components, it is common for errors to occur should the primary components need to be moved or changed. Developing a strategy for creating, maintaining, and organizing wall assemblies will allow walls to be swapped out at any time without the risk of moving walls due to differing reference points.

As Bim technology improves, the number of components which may be defined as secondary is increasing. Before they were made readily available, components like toilet partitions and fixed furnishings were not always graphically modeled. This is largely due to the amount of effort required to create a graphic representation of a component. As more manufacturers make their components available, the number of designers wanting to place them in their model increases.

Secondary components are essential to the design, but made remain largely unknown or undecided until later in design development. They rely on the dimensions and locations of the primary components for decision-making and product selection, and are generally non-structural in nature. The most common secondary components on projects are stairs and railings, fixtures and fittings, casework and cabinetry, specialty partitions, and certain types of fixed furnishings and storage. These types of components are essential to the understanding of spatial relationships, and the conceptualization of many aspects of the project. It gives the owner an understanding of what the space is used for. The walls may define the boundary of a kitchen, but the cabinets determine what it is.

If we think about different components in relationship to the overall size of the project, we can make the determination of how graphically accurate they need to be. Secondary components are those that are integral to the design, but not integral to the structure. In most cases these types of components are selected based on their appearance as much as they are based on their performance. When component is selected partially or entirely based on its aesthetic, how it is represented within the model becomes more important. The frequency at which these components are placed in the model is also a consideration when determining the graphic accuracy. If a component is placed in the project only once but is selected solely based on its aesthetic, it is reasonable to put more effort into its graphic accuracy, as maintaining its performance and file size is not as relevant as a component such as a door which may be placed hundreds of times throughout a single project.

Component size and location also come into play when considering the graphic accuracy of an object. A good rule of thumb is if you can't see it from 10 to 15 feet away in its installed position, don't spend a lot of time on it. This is a typical distance which is used for up-close rendering. Since the primary reason for making close representations of products is to improve the rendering aspect of the model, if it's not being rendered, it might as well be a cube. There are many components in a project that are actually very small. Whether it is a light switch, a drawer pull, or a window crank, deciding how accurate these components must be is important undertaking. While every manufacturer wants to think that their components are the most important, we have to look at the model in terms of scale. Ask yourself how important a window crank is to a 1,000,000 ft.² building, and what purpose it serves if it is not visible in rendered views. The answer lies in its ability to be quantified and qualified. If a component needs to be quantified or qualified, it can add value to the model. Let's go back to window hardware as an example and look at three possible scenarios: 1.) If a manufacturer offers several hardware options, and it will likely be visible in many rendered views, it should be added to the model graphically and have the ability to select options. 2.) If a manufacturer offers several options for the type of hardware used but it will not be seen in a rendered view, it is more effective to list the hardware as an attribute of the window without graphically modeling it. 3.) If only one type of hardware is available from the manufacturer, is perfectly acceptable to omit from both the graphics and the information contained in the project. If there are no choices which may be made, and the component is not commonly used for selection or specification purposes, then adding it to the model offers little value to the architect, specifier, or contractor.

Bob's BIM Tip: If you can't see a component from 10 to 15 feet away in its installed position, don't spend a lot of time on it.

Tertiary components are those which are added during detailing, or not at all. While it is my belief that every component that is used on a project should be brought into the model in some way, shape, or form, that does not necessarily mean it should be done graphically. There are ways to embed information regarding components without actually placing them in the project, and there are ways to simplify how a tertiary component is placed in a model as well. Hopefully this will minimize the number of tertiary components within a project, and increase the number of secondary components. Over time this could translate into more accurate models, and a greater demand for as-built models as a final deliverable to the owner.

A component like door hardware is an essential element within a project, is found in hundreds of locations, and even has its own special schedule, yet it is arguably a tertiary component which is often overlooked or omitted. Most architects choose not to deal with door hardware for the amount of effort necessary versus the benefit received from placing it in the model. Components like this are often better represented in context. Door hardware is a function of a door, and as such should be placed and controlled from within that door. Rather than attempting to place door hardware components at each location within the project, making door hardware a function of the door itself can allow it to be a graphic aspect of the model, and carry the important information to its respective schedules.

Accessories, movable furnishings, and equipment are tertiary components. Because they may be relocated at any time, and are more commonly used for conceptualization and space planning, these types of components are typically not modeled. As a general rule, when the placement of a component is not integral to the structure or the design of a project, the component can be considered "tertiary". Another way to look at it is if there is no specification section for the component within the project, it is probably a tertiary component.

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