Sharing High-Tech Tools Creates Rocky Mountain High

Denver's Unfathomable Form Brought in on Time and on Budget

5/15/2006 By Nadine M. Post

	Spirit of Collaboration. Architect Libeskind (left), client Sharp support cooperation, no confrontation, on tough job. (Images courtesy of Studio Daniel Libeskind LLC, left, DAM, top center, and M.A. Mortenson Co., right)

Another starchitect. Another unfathomable form. Another potential money sinkhole. On the surface, architect Daniel Libeskind's Denver Art Museum addition, a 146,000-sq-ft titanium-skinned "geode," had all the ingredients for disaster. Except in the eyes of M.A. Mortenson Co., which had recently cut its teethor been through the meat grinderon the monarch of all description-defying U.S. architectural icons, Los Angeles' Walt Disney Concert Hall. Instead of running scared, Mortenson salivated at the prospect of turning the agonies of Disney into the ecstacy of DAM. It landed the $70-million job in August 2001.

By all reports, Mortenson has succeeded at DAM, despite the job's geometric complexity. "It's been a great project," says Lewis I. Sharp, the museum's director. "Having just come off Disney was a big plus for Mortenson," he says. "Rather than being frightened by the new technology, Mortenson knew it could be the means to pull this off."

Sharp reports that, as first contracted with the city, DAM is "on budget and on schedule." Substantial completion is set for August. Opening day is Oct. 7.

Though the city owns the building, the private museum, under a contract to the city, is really the client. DAM's expansion, including Libeskind's Frederic C. Hamilton Building, is financed by $62.5 million in city bonds and $28 million in private funds.

Virtual Steel Work. 3D digital model for leaning structure included falsework, temporary steel, rigging frames and crane locations. (Rendering courtesy of Fred J. Fuhrmeister/Time Frame Photography, Photo courtesy of LPR)

Inspired by the Rocky Mountains while flying into Denver for his job interview, Libeskind started sketching the building on the back of his boarding pass. The sculptural addition, likened to a piece of origami for its many folds, angles and prows, will house special exhibits and galleries of modern and contemporary art, architecture, design and graphics. The five-level form is a series of spaces defined by nonorthogonal planar walls. There is little repetition and no typical floor.

DAM was the first public project in Denver to take advantage of a change in city rules, pushed by contractors and approved by the City Council in May 2001, that allows alternative project delivery systems, including construction management-general contracting, design-build and program management.

Studio Daniel Libeskind, New York City, was selected in July 2000. Libeskind then picked the local Davis Partnership as its joint-venture partner. Mortenson is the CM-GC, under a guaranteed-maximum-price contract.

The original construction schedule called for a 2004 completion. But among other things, an expanded scope and resequencing of related projects, including a parking structure, delayed the addition.

The role of CM and the contract award two years before groundbreaking gave Mortenson leave to form a strategy that included a preconstruction phasestarted in February 2002and computer-aided communication, coordination and construction. Mortenson pushed the sharing of three-dimensional (3D) electronic models between design and construction teams. Trust has replaced early suspicion, say sources. Collaboration, not confrontation is the job's mantra. A "spirit of resolving problems" was set early in the game by the client, says Tim Walsh, the vice president in charge of the job in Mortenson's Denver office.

Supermodel. DAM's steel erection sequence was so erratic, because of the building's inclined walls and lack of anything typical or repetitive, that erector LPR Construction Co. modeled the entire job in 3-D, including falsework, temporary steel, riggings and crane locations. (Image courtesy of LPR) MULTIMEDIA See more in a Windows Media animation. Click here >>

"The process was different from the traditional linear process," says J.R. Barker, project engineer with Structural Consultants Inc., the job's Denver-based steel-connection designer. "Once a week, Mortenson brought the entire design and construction team together and let them influence each other's lives," he says. "Decisions were based on what was best for the project, not for an individual."

The steel construction team agrees. "Everybody was scared to death of this project going in, but preplanning made things work," says Rocky Turner, president of Loveland, Colo.-based LPR Construction Co., the steel erector.

Cooperation is one of the main things that made this job different, adds Mark Zimmerman, president of local steel subcontractor, Zimmerman Metals Inc.

Teamwork. Mortenson, with leader Walsh (right), relied on preconsruction phase to work on constructibility issues with design team. (Phot courtesy of M.A. Mortenson Co.)

Even the architect gets stroked. "Libeskind's energy and passion inspired the team," says Walsh. Unlike some starchitects, "he goes out and mixes it up with the workers."

Libeskind, in turn, calls the workers, "heroes." Though not computer-literate himself, he values technology. "I could have designed the museum without computers but it could never have been built on time and on budget," he says.

	Sequence 13
	Toughest of the Tough. Sequence 13 had more than 50 sliedes to help workers visualize steps, both in 2D (top) and 3D (bottom three) (Images courtesy of LPR)

Though techno-soothsayers predict the coming of a single master digital model, for this job there was still one on the design side and one on the construction side. The architect and the CM each needed a full-time model keeper. One of the tasks was to coordinate with each other to keep the models in sync.

Mortensons 3D digital model, built from design-team models, included steel, concrete, ductwork, piping, conduit, fire sprinklers, scaffolds, temporary steel, falsework, crane locations, even rigging frames for steel lifts. It was used during construction for development and coordination of shop drawings, generated in 2D for field use. Mortensons 4D model, which added the element of time, was used for visualization and construction sequencingfor virtual prebuilding as a way to educate subs and anticipate and eliminate field problems.

Success hinged on getting the structural engineers digital wire-frame model to the steel detailer to create a solid model. At first, that did not sit well with the architect. I dont think any of us [on the design team] going in knew we were going down that roadgiving the contractor our 3D models, says Maria Cole, Daviss associate on DAM.

Believer

Skeptical at first, Davis is now a believer in sharing. Having the contractor on board early, studying the architects 3D model and physical scale models, and offering suggestions on constructibility, allows you to imagine spaces beyond what were capable of in 2D, Cole says.

Sharing digital models still puts challenges on design, says the architect. Certain things, lost in translation, need to be redrawn. Working with the model is cumbersome and time-consuming because it is information-intensive.

Arup, also the mechanical structural consultant, extracted valuable information from the architects volumetric digital models, including edge and top of flange and centerline of steel. Thanks to 3D, the firm was able to coordinate the frame, ductwork and piping, minimizing coordination-related requests for information. Every beam penetration was factory-cut and its location known during the design phase, says McConahey.

On the business side, Mortenson learned on Disneythe hard waythat to make the process work it is imperative to develop specific, detailed subcontractor contract language on generation and hand-off of electronic data. But all the models in the world wont help if people in the field arent familiar with the system. Its a learning process, says Walsh.

Biggest Bear

The steel frame was the biggest bear on the project. Mortenson had a process where issues were identified in a pre-detailing request and resolved through Web meetings and other correspondence. That, combined with use of the 3D digital model, prevented 1,200 collisions of steel elements and sped steel erection to the finish line three months early. Mortenson then gave nearly $400,000 back to the owner. The frame consists of mostly sloping columns with diagonal braces to resist lateral loads. There are about 40 different slopes. Perimeter walls lean outward from the horizontal 40 to 84. The only vertical elements other than some interior columns are elevator shafts.

The inclined walls generate permanent lateral loads throughout the floor system, which equate to similar design loads in a seismic zone, says Atila Zekioglu, an Arup principal. Horizontal beams, strategically placed, counteract instability of the inclines by acting like a tension tie.

Floor plates and individual roof planes are used as diaphragms to distribute lateral loads, with extensive use of drag-strut connections to distribute concentrated horizontal forces into the composite concrete-on-metal-deck diaphragm and back into perimeter walls and interior braced planes. Additional deck bracing and steel plates are under the deck in locations of high plane shear forces. Inclined walls are supported at ground level on vertical planes, where shear forces are transferred to reinforced concrete walls. Interior walls are supported on steel bracing in the vertical plane which in turn takes shear forces to caisson foundations.

Precambering was required on some joints in the frames vertical and horizontal directions to accommodate up to 3 in. of deflection when shoring was removed.

	In Time. 4D solid model, which even included concrete, "prebuilt" the job from bottom to top. (Image courtesy of M.A. Mortenson Co.)

Because of the unstable geometry, the erection sequence took precedence during preconstruction meetings. Sources say that when LPR spoke, everyoneeven the structural engineerlistened.

LPR created an 18-sequence erection plan for the 2,740 tons of steel. The plan, which included shoring, rigging design and crane reach drawings, was detailed in 3D, including step-by-step sequencing. Use of the 3D model in the office and the field was paramount to the projects success, says Curtis Mayes, LPRs director of preconstruction and engineering.

One of the toughest sequences was the erratic 13th, under the roofline. LPR could not figure out a reasonable way to shore the sequence, so it had to figure out how to stabilize members temporarily until other pieces were in place. Mayes used more than 50 3D slides to teach the sequence to the team.

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	Hollow Geode. No two floors of hte five-level museum have the same footprint. (Image courtesy of DAM/Miller Hare)

Coordinate geometry made alignment difficult. X-Y-Z survey coordinates were incorporated into the 3D model. All primary columns, sloping and vertical, were detailed and fabricated with shop-drilled control holes designed to hold a surveyors prism at a theoretical spot in space. A second survey location was fabricated into the member using a center-punch mark to locate and install a reflective target on the surface of the column. High-tech transits were programmed with the coordinates.

Zimmerman fabricated oversized bolt holes to allow the erector to use full-size fit-up pins. This was key to the fit-up, allowing easy field adjustment for imperfections in plate alignment, says LPR.

During design, Arup checked the structure and the mechanical service for clashes. The challenge was to place ductwork in the walls to minimize shaft space. The museum also wanted to minimize water piping in the art galleries. That meant home-running ductwork to central mechanical rooms containing air handlers. That was difficult because risers sloped every which way.

Inclined. Museum walls lean at about 40 different angles, making work more labor-intensive. (Images courtesy of M.A. Mortenson)

Arup laid out every duct run in 3D. When a run hit a steel member, a beam penetration was indicated on shop drawings and cut out during fabrication. Arup has already used 3D mechanical layouts on three other projects. Mostly it is used for mechanical rooms and tight ceiling-void pinch-points, says McConahey.

For the Loveland, Colo., office of U.S. Engineering Co., the mechanical subcontractor with a $6.3-million contract, the interface with other subs during Mortensons preconstruction phase was novel and helpful, as was the 3D solid model.

The jobs many bends were much easier to visualize in 3D. We used more offsets than we ever could have imagined and more support steel to support plumbing, says Daniel Kern, U.S. Engineerings project manager.

On the air side, it was also difficult to follow the planes.Nothing was square so we couldnt lay out normally, he says.

U.S. Engineering got involved in June 2003, replacing the original mechanical sub that had financial woes. We had to jump in quickly on the 3D portion, says Kern.

It was a learning process. Despite all the efforts, Kern says there were several collisions on each floor.

	Coordinated. Engineer ordered beam penetrations for duct runs. (Image courtesy of DAM/Miller Hare)

The electrical conduit followed. To lay out systems, Dynalectric Co. of Colorado, which has a $5.4-million contract, coordinated with mechanical and sprinkler contractors through Mortenson. The coordination was incredibly critical to locate their equipment, our equipment and how the systems run, says Craig W. Clark, president of the Lakewood, Colo.-based firm. I wouldnt say it was perfect but it worked quite well, he adds.

Clark says that with so many wall inclines, getting access to the top of each for lighting fixtures was difficult. Workers had to use mechanical lifts with arms, instead of ladders. The installation was about 40% more labor-intensive compared to a typical building. Its an OK job. I wouldnt say we got rich, he says.

Mortenson is already basking in the glow of its accomplishment, especially compared with Disney, although the concert hall was twice as big and in a high seismic zone. But Disney had 10,000 requests for information; DAM has 1,300. Disney, which opened in late 2003, has an outstanding claim, rumored close to settlement, of about $40 million. DAM has no claims pending or expected.

That said, without Disney there may not have been a DAM for Mortenson.