Imagine how much your operations and maintenance efficiency would improve if you had an owner's manual for each facility.
That's just what you'd get with building information modeling (BIM), which refers to both the computer modeling process and the resulting model itself. The newest versions of the software give designers, owners, and contractors a digital picture of all aspects — equipment as well as architectural and structural elements — of a building and make collaboration between the three much easier than earlier iterations.
The tool can be used at any stage of a facility's life, but provides the greatest long-term usefulness when deployed by designers at the project conception stage, and then by contractors through the construction phase. When the designer develops a model and passes it on to contractors, the contractors can do takeoffs, scheduling, and other construction planning with up-to-date information that's a virtual representation of the construction. The model can then be turned over to the owner as a highly detailed and accurate “as-built,” providing a reliable basis for decision-making throughout the facility's life.
The ability to add data is what makes BIM so powerful: It allows any individual user to do as much, or as little, with the tool as desired.
One example is the U.S. General Services Administration (GSA), which owns and leases more than 354 million square feet of space in 8,600 buildings in more than 2,200 communities nationwide. GSA has been taking advantage of the tool since 2003. GSA Building Information Modeling Guide Series 05 — Energy Performance describes how the organization is using emerging BIM-based energy modeling technologies to improve energy and thermal comfort performance in its current and future building stock.
“Energy modeling using BIM has the potential to simplify the process … by leveraging building information that exists in the architectural or mechanical models created by the project design team,” the guide says.
As a visualization tool, BIM helps everyone involved in a project to understand complicated space arrangements, such as in congested mechanical rooms. Unlike earlier visualization methods, however, it can include a wealth of information about each individual element. For instance, in addition to its dimensions and location, information about a pipe may also include its material, function, condition, and other parametric data.
Another useful feature, particularly for construction, is clash detection. Users can run a check at any time to identify interferences between different building elements. To avoid running exhaustive checks of every item each time the clash detection is invoked, the program can be set to check for interferences only between certain portions of the model; for example, mechanical piping and electrical conduits. Wise use of the clash detection feature can eliminate many, if not most, field interference problems before they have a chance to affect the construction schedule.
To make clash detection even more useful, attributes like access requirements can be modeled into a building element. “You can allow for the unseen,” says Robert Middlebrooks, AIA, industry programs manager for Autodesk Inc., provider of 2D and 3D design software. “For example, every valve that a worker needs to open or close needs some clearance around it, and you can build that into the model.”
Other examples include allowing space for a door to swing open where filters periodically must be changed, and ensuring that there is enough space near a ladder — perhaps a 3-foot clearance all around — so a person can climb it. With these attributes built into the model, users can run “soft” clash detections that report when a clearance has been compromised. This allows design adjustments to be made before construction or installation, eliminating long-term operational irritations.
Such requirements also can be applied to entire categories of elements.
“You may want to have 4 inches of clearance around every pipe to permit inspection and painting,” Middlebrooks says. “Each pipe already has attributes — size, material, thickness, function — and you just model the clearance requirement as additional data tied to an attribute.” Having gone beyond constructability issues, the program helps create a facility that is maintainable and easy to operate.
TURNING DATA INTO PICTURES
BIM uses a structure reminiscent of a relational database, and the core model often consists of a number of individual models aggregated together. Depending on the particular project, either the architect or design engineer may put together the core model. Others, such as the mechanical and electrical contractors, put together their own models that are then tied into the core model, not unlike layers on a CAD drawing. Embedded in each of the models is any information the user chooses to include.
Some software is bidirectional and reflects changes made on any of the secondary models throughout the entire model. Other programs are unidirectional, accepting changes made on the secondary models only as imported data to the main model.
Individual programs use a variety of file formats, but most support more than their native file formats. Tekla Structures, for example, supports IFC, DGN, DWG, XML, and other nonproprietary formats for model and data aggregation activities. Some programs have built-in translation capabilities; for example, Autodesk and Bentley Systems Inc. have an interoperability agreement that enables each program to read and write the other's native formats.
In general, however, BIM technology is still at the point where having a good utility program to manage the translation and meld data is worthwhile.
One such program is Autodesk's Navis-Works, a nonproprietary aggregator that combines data from virtually any BIM-related program. Its modules allow you to work with the model as well as view it. Whereas the actual BIM programs are the tools for design activities, this aggregator is a good tool for the construction and execution of a project.
Phoenix-based general contractor Sundt Construction uses NavisWorks for viewing and investigating models as well as for visualizing how concrete elements fit with other building systems. (See Web extra on page 33.)
For example, a recent project called for two 6-foot-square spread footings just 2 feet apart. Ordinarily, says Sundt's Simulated Construction Manager Dan Russell, the crew would form a single 6x14-foot placement. But a quick look at the building model showed floor drains and piping in the 2-foot space, so he told the crew not to combine the two footings.
Another viewing tool is Adobe Acrobat's 9 Pro Extended version, which converts a BIM model in IFC format to a PDF with full visualization capabilities and access to the object property data associated with the model.