Contractors building one of the largest and tallest pediatric research hospitals, hemmed in on a tiny site in Chicago, say they are several months ahead of schedule in part due to the owner�s requirement that designers and contractors collaborate using building information modeling, a digital tool that helps prevent errors. However, the use of BIM apparently still has some growing up to do. For the 1.25-million-sq-ft hospital that stands 457 ft tall on just 1.8 acres, the building team not only is tackling the challenges of urban, vertical hospital construction, it also is conducting research to determine if the time and cost of modeling the hospital, down to its mechanical hangers, is adding value to the project.
Armed with laser scanners and their resulting �point cloud� diagrams, construction managers are beginning to compare BIMs to what was built. Early results of the reality check are in, even as the fast-tracked project is just 50% complete.
The scans are expected to go a long way toward understanding what is and isn�t creating value. No one knows for sure what the BIM effort cost, but one project executive, Bob Gallo, guesses it saved seven figures. �The expectation is the premium up front pays for itself [in the] long term,� says the senior vice president of Power Construction Co., Schaumburg, Ill. The firm is in a 50-50 construction management-at-risk joint venture with Minneapolis-based M.A. Mortenson Co. to deliver the $1-billion Ann and Robert H. Lurie Children�s Hospital of Chicago.
�The real question � is, what�s adding value to the project?� says Stuart Baur, project manager in the Los Angeles office of Zimmer Gunsul Frasca Architects LLP, the project�s lead designer. �We could model loose-hung cable and J-hooks, but do we add value by doing that?�
The tiny site inspired a high-rise hospital. The emergency room, for example, is located on the second floor, requiring extra elevators and a special state permit. The bed tower starts on level 14 of the 23-story building. There, the L-shaped plan becomes two squares. Floors are roughly 50,000 to 60,000 sq ft.
The building, which topped out last fall and is on course to be delivered by June 2012, has a steel frame with a shear-wall concrete core, designed by structural engineer Magnusson Klemencic Associates, Seattle. Floor-to-floor height is about 17 ft up to the mechanical level 10, which has a 42-ft-high ceiling. Above that, the floor plate expands to provide a bilaterally symmetrical floor for the nursing staff. To allow this, the engineer devised a 90-ft-deep supertruss, from levels 16 to 22, creating a 180-ft-long 30-ft cantilever over an easement that runs along the building�s east side. Truss loads bear on the first set of internal columns.
BIM There, Done That
Most of the building team already was well-versed in BIM, or 3D parametric modeling, but none had modeled a project quite this big. Due to its digital emphasis as well as legal issues, the project has morphed into a hybrid between collaborative, or integrated, delivery, design-build and conventional building.
The owner ruled out integrated project delivery with a multiparty contract, which is popular with some hospital developers. �I�m still not convinced you have as much of a competitive situation� with IPD, says Bruce Komiske, Children�s chief of design and construction. Rather than parties sharing models, designers created their own models, and prospective contractors were brought on as consultants during the design phase. The CM bid out subcontracts competitively last year. Then, construction models were added to the design model without an implied right of reliance. But common to IPD, the building team was collocated.
Each firm forced BIM to grow up a little for Children�s, where use of BIM was not negotiable. �There were a lot of challenges in the beginning, particularly on the technology side,� says Komiske. The end result is a lot of models: There are currently more than 50 primary models and thousands of smaller models.
For all its 3D complexity, however, not everything at Children�s is modeled, and there�s a reason for that: Only elements one inch or greater in size are included�a rule established in the team�s protocol manual. The idea is that something as small as �-in. pipe�effectively spaghetti to a constructor�can be worked out in the field without extra expense. �It�s a lot about time versus value in today�s current state,� says Peter Rumpf, senior integrated construction coordinator for Mortenson. �But I don�t think that it�s too far off where we�ll add that extra level of granularity.� With BIM, he adds, more is usually better. �Whatever is not in the model is going to come back to haunt you. We want to get as much information in there as possible,� he says.
Prior to construction, BIM provided a helping hand with coordination inside the building�s most complex space: a 60,000-sq-ft, 42-ft-high mechanical room with three levels of ductwork and air-handing equipment. �I�d like to think that, without BIM, it would have been nearly impossible to build,� says Jason Smith, chief engineer for mechanical contractor F.E. Moran, Northbrook, Ill. About 250 tons of sheet metal�prefabricated from 3D models�had been installed by last month, when crews took down the second tower crane.
Despite the project�s digital savvy, participants admit they are not using BIM to its full potential. Field crews still are building from 2D paper plans, which remain the official contract documents. Design and construction models still are segregated for liability reasons. The owner doubts it will achieve what some believe to be BIM�s Holy Grail: using the data for facility management. �We teed it up to knock it out of the park, and yet we still have a ways to go in the industry,� Rumpf says.
Enter the lasers, a tool helping to close the digital divide. Mortenson/Power is using them to audit contractors� work and, indirectly, to conduct BIM research. The CM has shot portions of three floors�about 20,000 sq ft�at a cost of under $10,000. Superimposing the point clouds...