...on the BIMs, engineers are visually checking discrepancies between BIMs and reality. �[BIM] allows us to trim the fat,� Rumpf says. The hard part is to accurately measure the savings. So far, the discrepancies have been minor .

Ground Rules

During a kickoff meeting in 2006, ZGF, its subconsultants and the CM developed their own BIM protocol manual, a roughly 40-page document that remains largely unchanged today.

The team then tested the protocols by creating a digital model of a 10,000-sq-ft building. �It gave us the opportunity on a very small scale to test all the scope issues,� says Baur. The manual�s final draft was issued four months later, in fall 2006, before ZGF began design work.

Firms were asked to share their models. �It was very clear� that we all needed to work together relative to BIM, says Baur. Yet designers would not vouch for their models� accuracy because existing insurance products would not cover problems arising from digital sharing. �We simply couldn�t warrant the contract documents were identical to the model, and that�s an issue the industry needs to resolve,� Baur says.

A design-intent model (DIM) emerged on the design side, followed by what has become the industry custom: a more detailed fabrication model for major systems, including ductwork and steel. The resulting models had to be sorted out by dozens of modeling engineers and coordinators. Five design models emerged�enclosure, structure, bed tower, diagnostic and treatment floors, and mechanical systems�and 48 fabrication models followed. When disagreements arise among the subs during clash-detection meetings, Mortenson/Power referees. �Its our job to decide whatever directive is given is in the owner�s best interest,� says Rumpf.

Aside from the liability concern, pushing 3D data from this project into the field has been a struggle. One reason is that, while used on this job for quality control, digital displays such as tablet PCs are still not large or flexible enough to replace the paper drawings. �We just haven�t made that leap yet,� says Smith, who adds that robotic total stations have complemented paper plans by helping installers reference location against the model in real time and without measuring tape.

Subcontractors note that, as is now common in the industry, BIM helped them work out clashes. It also helps installers make sure their aerial lifts go up with the proper nuts and bolts. �With BIM, you can develop these bills of materials, and the computer will tell you exactly what you need,� says Smith.

Fine-Tuning

Though BIM simplified the complicated mechanical floor, it didn�t help all that much with the cantilevered, 10-story bed tower. The frame had to be erected this past winter without falsework due to site constraints. The procedure�designed by Farmington Hills, Mich.-based Ruby+Associates under the direction of subcontractor Chicago Steel and fabricator Zalk Josephs, Stoughton, Wis.�involved hanging the truss on steel suspension cables, which temporarily were tied back into columns and floor beams.

Mortenson/Power originally had proposed building up from the 16th floor, then coming back down to finish the truss. Because the upper floors would obstruct part of the work below, some were concerned the project�s tower cranes would have trouble accessing it.

Ruby proposed building the cantilever from the bottom up, but it had no built-in means of supporting it during construction. �That�s where the cable system came in,� says Ronald O. Goetze, Ruby�s project engineer. A system of 48 tieback cables, �-in. to 11?8-in. in dia, were rigged from the cantilever beams, over column-hung pulleys and tied back into the main floor beams. The cables at their termination points were fitted with turnbuckles so that ironworkers could slowly relax the loading of the floors, set 2 in. to 3 in. higher than designed, after all the steel was in place, to avoid shock-loading. The rigging supported the cantilever like �a little crane,� says Goetze, who adds the procedure took nine months to plan and about two months to execute.

Lower down, the building also tricks the eye. Transfer girders at levels 3 and 5 and a transfer truss at level 10 eliminated 18 of 80 columns at ground level due to at-grade obstructions, such as access drives. �If you talk about developing an office building, a lot of those buildings are really designed from the outside in,� says Bob Anderson, an MKA principal. Hospitals, he adds, �really are designed from the inside out because the program and the function drives the building.�

Role Model?

Children�s is an example of how the construction industry struggles to embrace technology so that its players can work together better, experts say. Yet at the same time, the project shows how far the industry has come. �It has been a tremendous challenge, and I absolutely would do it again in a heartbeat,� says Baur.