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What is a Building Information Model?

BIM is a process by which digital representation of physical and functional characteristics of a facility are built analyzed, documented, and assessed virtually, then revised iteratively until the optimal “model” is documented. The process then continues through construction and construction as-built documentation and again during the lifetime of the facility. As such, it serves as a shared knowledge resource for information about a facility forming a reliable basis for decisions during its lifecycle from inception onward. BIM is more than 3D modeling, although the 3D model is the geometric platform on which BIM operates. The ability to assign attributes and data to the objects in a 3D model is an important consideration in differentiating a 3D model from a building information model. A building information model may be best described by its key features:

3D parametric modeling:
3D modeling is a superior design environment when compared to traditional 2D CAD. Mainstream 3D modeling applications have the ability to parametrically capture design intent which facilitates model creation and editing and therefore reduces the likelihood of coordination errors. Although preparation of the 3D model may be the significant part of most BIM efforts, a model alone does not constitute BIM.

Engineering Analysis:
At the core of BIM lies a digital database where objects, spaces, and facility characteristics are each defined and stored. These characteristics make it possible to use BIM as a virtual representative of a physical facility and are hence able to perform qualitative and quantitative analyses. These BIM-enabled analyses, be it for structural, energy consumption, day light analysis or a number of other performance simulations, can significantly enhance the efficiency and efficacy of the design, planning and building processes.

Clash detection:
Since the 3D model represents virtual true space, a BIM process known as “clash detection” can be utilized to check for interferences by searching for intersecting volumes. It is often the case to use a third party application to not only clash a single model but combine and clash multiple models from disparate sources in a common environment.

4D Schedules:
A 4D BIM scheduling application can link CPM schedule activities to 3D objects. This allows for a graphically rich and animated representation of the planned construction sequence set against time. 4D schedules are a powerful tool for phasing, coordinating and communicating planned work to a variety of audiences including project stakeholders and those directly responsible for executing the work.

Cost attributing:
As part of the BIM process, cost data can be associated with each element resulting in a detailed cost schedule. This “cost attributing” is parametric and dynamic so that any change to the model will result in a change to the bill of materials and project cost estimate.

General information attributing:
3D objects can also be linked to a variety of source documents via hyperlinks. This enables the model to function as a Graphical Information System (GIS) for the building. Project correspondences, technical data, O&M records, and links to manufactures’ websites are all possible in this environment. Information attributing via hyperlinks can add value to all phases but is typically associated with facility management functions.