BIM is a huge buzzword in AEC. It shows up in every magazine; there are multiple conferences a year about it; software developers headline their products as BIM tools. What is it? How is it different? Why should an architect or contractor care about BIM?
What BIM is and Why is it Different?
For all of the history, design and construction of building have relied on drawings for representing the work to be done. They were defined as contracts - legal documents, were assessed by building codes, and used to manage the facility afterward. But there are two strategic limitations of drawings: (1) they require multiple views to depict a 3D object in adequate detail for construction, making them highly redundant and thus open to errors; (2) they are stored as lines, arcs and text annotations that is only interpretable by some people; they cannot be interpreted by computers.
BIM involves representing a design as objects – vague and undefined, generic or product-specific, solid shapes or void-space oriented (like the shape of a room), that carry their geometry, relations and attributes. The geometry may be 2D or 3D. The objects may be abstract and conceptual or construction detailed. Composed together these objects define a building model (not a BIM, in my view). If an object is changed or moved, it need only be acted on once. BIM design tools then allow for extracting different views from a building model for drawing production and other uses. These different views are automatically consistent - in the sense that the objects are all of a consistent size, location, specification - since each object instance is defined only once, just as in reality. Drawing consistency eliminates many errors.
Modern BIM design tools go further. They define objects parametrically. That is, the objects are defined as parameters and relations to other objects, so that if a related object changes, this one will also. Parametric objects automatically re-build themselves according to the rules embedded in them. The rules may be simple, requiring a window to be wholly within a wall, and moving the window with the wall, or complex defining size ranges, and detailing, such as the physical connection between a steel beam and column.
Why BIM is Important
Because 3D objects are machine readable, spatial conflicts in a building model can be checked automatically. Because of this capability, at both the design and shop drawing levels, errors and change orders due to internal errors are greatly reduced. Pieces can carry attributes for selecting and ordering them automatically, providing cost estimates and well as material tracking and ordering. Thus as a building representation, BIM technology is far superior to drawings. This is very clear for contractors and fabricators, but what about architects?
The larger implications of BIM are not just consistent drawings, cost estimation and bills of material and clash detection. Because building models are machine readable, it becomes practical to use the data they carry in many other ways: for energy, lighting, acoustic or other analyses - not as post facto checking if an almost finished design is "OK", but rather to provide feedback while designing, informing the designer of the effects of changes or to explore the relative effect on alternatives. Thus building models allow for better integration of design processes, allowing the kind of exploration that is equivalent to having a team of analyst consultants assessing your design as you make explorations. The result is that designers taking advantage of BIM can develop and demonstrate design trade-offs in ways that have been impossible in practice until now, and providing better services. Many of the uses of BIM data are waiting to be discovered and developed.
While building modeling first gained recognition among architects because it was the only way to get blob buildings and exotic forms constructed, big payoffs can be gained for even simple buildings. Building models can save costs, save construction time, and support better building performance and control. It can potentially beneficially impact all parties in the construction process - designers, engineers, contractors, fabricators, facility operators. the whole construction industry as well a owners. In this sense, BIM is similar to the automation of manufacturing in the 1980s, when most manufacturing industries first adopted 3D modeling and digital representations. The changer of ways of operating in manufacturing are still evolving.
These capabilities also facilitate much improved coordination and collaboration. Designing a building once for contract drawings, then developing a set of detailed drawings for shop fabrication is recognized as involving much waste and inefficiency. Design-build and other forms of architect-contractor teaming have been recognized as more efficient - in terms of cost, time, and for reducing the potential for litigation. Building models tremendously facilitate this process. A 3D model is easier for all parties to interpret and visualize. Design or fabrication work can be coordinated in person or at a distance using web conferencing tools such as Webex and GoToMeeting and virtually walking through the 3D model.
Owners are recognizing the performance benefits offered by BIM, in terms of reduced cost and change orders, in terms of better building performance, -- and as a result are increasingly requiring it. Examples include GSA, DOD, the state of Wisconsin and other government organizations, as well as universities and health groups.
Definitions of "BIM"?
Some people have called the building model "a BIM" - that Revit or ArchiCAD or Bentley generate a BIM. Others say that the representation is not as important as the process of going to machine readable model(s) because machine readability opens up so many opportunities for further integration and automation. Above, I have referred to a building model as the basis for BIM, and implied that BIM is a process. This definition is consistent with that outlined by GSA, on their BIM website, at: http://www.gsa.gov/bim. The process of BIM is revolutionary because it provides the opportunity to migrate from practices that are centered around human craftsmanship to a more augmented and modern machine craftsmanship - and all that this might imply.
Will it Become Standard?
BIM tools are as different from CADD tools, in the same way that a slide rule is different from a computer, or as a set of toy soldiers is different from a battle-oriented computer game. BIM supports on-line simulation of a design, on-line simulation of construction - called 4D CAD, on-line simulation of a building’s operation, mechanically as well as the people organizations within it. The BIM processes provide better building products at lower costs to the owner. A growing number of case studies (some on this website) have shown the benefits to users who have used a building model to apply BIM technology. Building models and BIM technology will certainly become the standard representation and practice for construction within most of our lifetimes.
BIM Handbook by Chuck Eastman BIM Handbook: A Guide to Building Information Modeling for Owners, Managers, Designers, Engineers and Contractors
by Chuck Eastman, Paul Teicholz, Rafael Sacks, Kathleen Liston
> Table of contencts
More BIM descriptions by others
A computable representation of the physical and functional characteristics of a facility and its related project/life-cycle information using open industry standards to inform business decision making for realizing better value
(NIBS - Facility Information Council);
Information use, reuse, and exchange with integrated 3D-2D model-based technology, of which electronic documents are just a single component (AEC Infosystems, http://www.aia.org/tap_a_0903bim);
A single repository including both graphical documents - drawings - and non-graphical documents - specification, schedules, and other data (ArchiCAD);
A modeling of both graphical and non graphical aspect of the entire Building Life cycle in a federated database management system (Bentley);
A building design and documentation methodology characterized by the creation and use of coordinated, internally consistent computable information about a building project in design and construction (AutoDesk)
These are some descriptions of BIM from different groups. The underlying concept dates back to early 70s, when people thought about intelligent CAD system. Some of the BIM tools has been in the market for 20 years.
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