Santa Clara, California
For five uneasy years, the building team responsible for delivering the San Francisco 49ers' $1 billion new home had hung together through three work hiatuses, a recession, and a regrouping caused by a site relocation 45 miles to the south—from San Francisco's Candlestick Point to Silicon Valley's Santa Clara. Then, in early fall 2011, things changed. Suddenly the snail's pace became a race.
Based on an early opportunity to secure financing, the 49ers and the Santa Clara Stadium Authority, which will own the new Santa Clara Stadium, decided to accelerate the opening by one year. They are pulling out all the stops to finish in time for the 2014 NFL season. “It was like drag racers warming up their tires with short bursts forward at the starting line before the race begins,” says Jon D. Magnusson, president and CEO of the project's Seattle-based structural-engineering firm, Magnusson Klemencic Associates (MKA). “Then, all of a sudden, it was go, go, go.”
Plans by the Los Angeles office of HNTB Architecture call for a nearly 1.9 million-square-foot facility with 68,500 permanent seats and the ability to expand capacity to 75,000 for the Super Bowl. A nine-story tower capped with a roof terrace will house the venue's 165 suites. For construction, the stadium authority named the 49ers' Stadium Development Company (StadCo) as its agent. It will lease the facility under a long-term agreement. Major financing is from a group of banks led by Goldman Sachs.
The project has at least two claims to fame. The 49ers team is the first sports franchise—and perhaps the first organization of any kind—to use a hybrid, collaborative project-delivery model that Magnusson dubbed integrated bridging design-build (IBDB). “We landed on this delivery system in 2005 after looking at prior stadium projects with cost overruns and disputes between the owner, the architect, and the contractor,” says Larry MacNeil, the 49ers' executive vice president for development. “We are trying to eliminate potential disputes and limit the owner's ultimate risk.”
The second distinction is that the steel structure, designed to resist seismic loads through a braced frame, is the first NFL stadium to use buckling-restrained braces (BRBs). The 529 BRBs, which resist lateral loads, have structural and architectural benefits, in terms of earthquake resistance and design flexibility, over conventional braced frames or shear-wall structures (see sidebar, opposite page). “This is the most extensive use of BRBs on any sports facility, to my knowledge,” says Wayne Searle, CEO of SME Steel of West Jordan, Utah, which is the lead firm for the project's steel contractor, the SME/Hirschfeld Joint Venture.
The IBDB delivery model is an enhancement of bridging design-build. Under bridging, the design team selected by the owner takes the project through design development. The owner then typically selects a design-build contractor, and that contractor, in turn, hires its own designers of record. But under IBDB, the architect and engineer that first work for the owner are transferred to the design-build contractor and become the designers of record in the design-build phase. “For this project, in a seismic zone, the need for continuity of the structural engineer from start to finish is paramount,” says Jeffrey R. Appelbaum, managing director of Cleveland-based Project Management Consultants (PMC).
PMC crafted the delivery model for the 49ers based on bridging design-build models developed for other sports venues. And to help the architects resist pressure to compromise the architecture during the design-build phase, the 49ers have “contract limits with HNTB that say it will not produce any design in phase two that would be inconsistent with phase-one design,” says Appelbaum.
The “integrated” in IBDB means the presumptive design-build contractor is brought in at the project's onset to help with estimates and constructibility under a preconstruction-services contract. The owner has the option to hire a different design-build contractor if it is not satisfied with its proposed guaranteed maximum price (GMP), or for any other reason. Major subcontractors are also brought in early to assist with design.
The 49ers hired the local Turner/Devcon Joint Venture for preconstruction services one month before hiring HNTB. But the Santa Clara–based 49ers and Devcon Construction, of Milpitas, California, go way back. The 49ers first engaged Devcon, which is well established in the Santa Clara area, for preconstruction services in mid-1997, when San Francisco passed ballot measures for the stadium and a mall project at Candlestick Point, the 49ers' current home. That effort went dormant in 1998. Devcon continued to assist the 49ers with estimates and other services.
The project almost came alive again in 2001, but no team was selected. Then, in 2006, the 49ers issued two requests for proposals (RFPs)—one for the architect and one for preconstruction services. That RFP had Devcon listed as a partner, says Jonathan Harvey, the joint venture's codirector and a Devcon vice president. In March 2006, the San Francisco office of Turner Construction was selected as the national contractor with sports construction experience. The site switch and a modest redesign happened in 2008.
StadCo retained the joint venture as the design-build contractor earlier this year after a GMP had been established. Turner/Devcon's $854 million design-build contract is actually with the stadium authority. HNTB and MKA's contracts were transferred to Turner/Devcon in June.
The job kicked into high gear over Labor Day weekend in 2011, when the 49ers' MacNeil gathered his team to consider whether an early completion was doable. Within a few days, the members of the building team, who had been working together on and off for five years, decided they could get the job done, but it would mean pushing hard. To regroup, the team, among other tactics, phased and streamlined the design schedule, “stacking it” over construction. “We shortened design by seven months and went out to bid seven months earlier,” says Harvey.
Speeding things up was not easy, adds David J. Masel, Turner/Devcon's general superintendent and the acknowledged mastermind of the “rush” strategy. “We had to take into account all contingencies. We didn't have the design or drawings, so we plugged historical data into scopes of work,” he says.
Buy-in from all of the design and construction teammates—from individuals, not just the firms—was essential for the accelerated plan to work, says Jack W. Hill, StadCo's project executive. Hill, an owner's representative based in Dallas, joined the team over that Labor Day weekend.
IBDB allowed the team to quickly devise a phased permitting plan and site-utilization and staging plans. The full-team cooperation allowed HNTB to obtain commitments from MKA on a phased delivery of documents for structural packages and on a greater overlap of design and construction than is typical, says Hill. “There are probably not too many projects with as much camaraderie and connectivity,” says Joseph J. Diesko, HNTB's vice president and director of sports architecture. “A lot of owners believe adversarial relationships produce better results,” he adds. “That is not the case here. This has been a great process.”
In the accelerated scheme, structural steel was on the schedule's critical path. Turner/Devcon first asked MKA what could be done to get the basic steel design in a huge hurry—by early November 2011. “Then we worked with our estimators to make sure the right allowances were in the estimates,” says Robert L. Rayborn, the joint venture's co-director and a Turner construction executive.
As a result, in the middle of design development, MKA moved into construction documents. “We had to consider the structural set and let MKA go, or we would not be able to coordinate the mill orders,” says Diesko. The architect “froze” the structure, as if it were an existing building, much earlier than is typical, adds Lanson Nichols, an HNTB vice president.
The strategy worked. “We got our first design-development package to buy structural steel and vertical transportation in November 2011,” says Harvey.
After design development, the new schedule eliminated a typical “pencils down” period for the design team—a period the design-builder would normally use to create the GMP. The strategy sliced two months off the project's 28-month construction schedule. Turner/Devcon's contract calls for substantial completion in August 2014. That cuts out a typical three-month buffer between substantial completion and the first game.
About a year ago, the team met with the city to develop a multiple drawing-package review strategy for phased permitting of the steel structure, the foundations, and the concrete. To expedite the steel permit, MKA proposed combining a peer review of the structure, which the 49ers wanted, with plan checking. For this, the city agreed to deputize Los Angeles–based structural reviewer John A. Martin & Associates as part of the building department.
MKA split the structure into eight plan-check packages, submitting them in stages from November 4 to February 17. While Martin & Associates reviewed one package, MKA continued to engineer others. This strategy saved at least two months over a more typical two-step foundation-and-superstructure review process, says Brian A. Dickson, an MKA principal.
Construction began on April 23 and has been speeding along. One of Turner/Devcon's strategies for accelerating the work was splitting the building into four quadrants and constructing them concurrently instead of relying on more traditional, “racetrack” oval sequencing. Crews used four drill rigs for the auger-cast piles and are erecting steel with four crawler cranes, one for each quadrant.
Turner/Devcon is using building-information modeling (BIM) for interference checking. To date, there are 402 requests for information, instead of three or four times that amount, thanks to IBDB with BIM, says Harvey. BIM also was used to locate and build the deep utilities below the slab on grade so they could be built ahead of piles instead of afterward. Crews worked 24-hour shifts from May 1 to May 15. That move cut the time in half for the deep utilities work, says Harvey.
Steel erection began on July 30, with topping out expected later this month. On September 4, tower cranes started lifting in escalators. And in late October, crews installed the first piece of structural precast concrete for the seating treads and risers. The project is on course for substantial completion one month ahead of the accelerated schedule, says Harvey.
The IBDB and acceleration strategies have worked out so far, says the 49ers' MacNeil. “We are pleased with the design-build team,” he adds. But with about a quarter of the project complete, construction isn't slowing down. Says MKA's Magnusson, returning to his drag-racing metaphor, “We haven't deployed the parachute yet.”
49ers Seismic Solution Is an NFL Stadium First
During both the conceptual and schematic design phases for the San Francisco 49ers' stadium, the structural engineer developed a matrix of 66 structural-system scenarios. Then the design and construction team evaluated each for schedule and cost. The team ultimately selected a steel frame, with composite metal decking and structural precast seating treads and risers. Buckling-restrained braces (BRBs) resist earthquake loads.
'A BRB works like an ordinary steel brace but performs better under seismic loads due to the fabrication of a brace with 'controlled' tension and compression capacity,' says Brian A. Dickson, a principal with the stadium's structural engineer, Magnusson Klemencic Associates. A BRB system uses significantly less steel than an equivalent moment-resisting frame. An equivalent concrete shear-wall system would weigh six times more. Compared with other systems, the reduction in weight and the better seismic performance translate into savings in foundations. 'We estimated foundation costs to be 20 percent less than if a concrete shear-wall system were used,' says Dickson.
Each of the 529 BRBs has a steel core surrounded by concrete mortar encased in a steel tube. The high-performance braces are on every level of the new Santa Clara Stadium, which varies in height from four to eight stories. The BRBs range in weight from 2,500 pounds to 13 tons and are up to two feet in diameter near the base, where seismic forces will be greater. BRBs interfere less with the architecture, particularly the floor layouts. They also allow a more open look. And they are no more difficult to erect than conventional braces. Begun on July 30, steel erection for the 1.9 million-square-foot project is more than 90 percent complete. N.M.P.
Nadine M. Post is editor at large at Record’s sister publication Engineering News-Record.