Canada’s $730-million Vancouver convention center expansion on the city’s waterfront sits on the best of sites. To the north are breathtaking views of Coal Harbor, Burrard Inlet and the North Shore Mountains. Across the street to the south is the city center. Directly to the west is the landmark Stanley Park.
But the 106,000-sq-meter project in seismic British Columbia also sits on the worst of sites: The 11-acre brownfield, which consists of fill with remnants of rail yards and an industrial past, was the most contaminated in the harbor. A remediation removed 10 ft of earth, followed by soil densification. At high tide, the building’s footprint is nearly two-thirds over water, which forced workers to drive many of the 1,000 steel piles only at low tide, at times working from barges to build the concrete marine platform and the steel superstructure.
The waterfront location also called for creation of an artificial reef—a habitat apron—to mitigate the development’s impact on coastal marine life. Water on three sides and a city street along the fourth also restricted access to the site, which meant the platform had to be designed to take hefty crane loads.
“This is probably one of the best sites we’ve ever had, but there are unique conditions,” says Tom Burgess, project manager for Seattle-based LMN Architects, design architect for the Vancouver Convention Center Expansion Project Inc. (VCCEP). Local Musson Cattell Mackey Partnership and Downs/Archambault & Partners are the prime architect.
The $434-million construction project is on schedule for completion on March 15. The program includes a 23,226-sq-m exhibit hall, 7,711 sq m of meeting space, a 4,645-sq-m ballroom, 8,361 sq m of streetfront retail, 37,161 sq m of walkways, bikeways, public plazas and parking for 443 vehicles. A viaduct is being built along the southern elevation. There are also two elevated, enclosed walkways, one leading to the existing convention center, which is also getting a lobby upgrade, the other to a new hotel.
The building has a structural glass curtain wall that makes it look like a “glowing lantern” at night, says LMN. It’s “fifth face,” a roof visible from nearby high-rises, is camouflaged by a 2.4-hectare garden. LMN knows of no larger “living” roof on a convention center. The architect thinks it is the second largest green roof in North America and the largest in Canada. Though there is no public access, plantings can be seen from inside the building, thanks to the slopes and cants of the “folded” roof plate.
The design team had to cater to three habitat layers: marine, human and garden birds and insects. “It’s more than a building, it’s a piece of the waterfront and park ecosystems,” says Mark Reddington, LMN’s design partner.
The project, which includes a wastewater treatment system to turn “blackwater” into graywater for toilet flushing and roof-garden irrigation, is going for a LEED Gold rating from the U.S. Green Building Council’s Leadership in Energy and Environmental Design. It will be the only convention center in a high seismic zone with the rating and only the second LEED Gold convention center in North America, say sources.
There were zoning restrictions on height, width and depth to protect view corridors. As a consequence, the exhibit hall had to be at grade instead of at an accommodating higher level and translated to heavier “ceiling” trusses to create large bays. On the west half, the building is mostly two levels; on the east half, program space is stacked in up to six levels.
The harbor site meant no basement for equipment and parking, and the planted roof meant no space for cooling towers. There is no “back door” and no “place to throw all our toys,” says Blair McCarry, project principal in the local office of the mechanical-electrical-plumbing engineer, Stantec Consulting.
The lack of space resulted in what LMN calls “program compression.” Reminiscent of the firm’s Hawaii Convention Center, parking is squeezed into the 4.5-m-deep transfer-truss level between the ballroom above and the platform-level exhibit hall.
For the builders, the biggest difficulty was working over water, says Robert J. Smith, project director for PCL Constructors Westcoast Inc., the local construction manager. For PCL, the next biggest challenge was “a very busy industry,” with a shortage of local trades to bid work and a shortage of labor.
The $83-million foundation took a year to build. To keep to the schedule, platform design had to be done before superstructure loads were set. With so many unknowns, foundation design was conservative.
“It was a challenge from the get-go,” says Ryan MacPherson, project engineer for WorleyParsons Westmar, North Vancouver, British Columbia, which designed the foundation and platform.
The interface between the 341-meter x 168-m platform and steel superstructure columns was one of the most challenging aspects of the job, says David N. Walker, project manager for the public VCCEP, a division of BC Pavilion Corp. (Pavco is a wholly owned subsidiary of the province of British Columbia.) Walker says the site added to cost, though a comparison to a greenfield site was not done.
The glass curtain wall, the high seismic zone, the sloping columns on the north face and irregular geometry throughout complicated superstructure design and construction. The lateral system had no solid perimeter or core needed to resist seismic loads, says Rob Simpson, a principal of local structural engineer Glotman Simpson. This disadvantage was especially noticeable in the taller section, where interior walls rarely line up floor to floor.
“This is...one of the more difficult frames we’ve erected,” says Jim McLagan, vice president of local steel contractor Canron Western Constructors Ltd.
The expansion has been in the works since the early 1990s, when the original 1987 convention center reached capacity. In 2002, after consideration of several sites, design concepts, forms of project delivery, ownership and funding mixes, things fell into place.
Of total costs, $418.2 million is from the province, $188.4 million from the federal government and $76.7 million from the city. The remaining $59.8 million is from convention-center revenue.
VCCEP hired LMN in 2002. In February 2004, VCCEP brought in PCL for preconstruction services and selected other design consultants. From construction’s start in October 2004 until April 2007, PCL served as construction manager under a lump-sum contract. The agreement was then converted into a guaranteed-maximum-price contract.
The strategy was to phase the work by splitting the building in half along its north-south expansion joint. The expansion joint was required to handle differential thermal movement caused by the platform’s exposure to the elements in the marine environment. The joint also helps reduce torsion from the eccentric frame.
Design and construction moved east, where the most of the area is, to west. The job was “creatively” phased, staged and sequenced to keep design and construction moving, says LMN’s Burgess.
After remediation, local Vancouver Pile Driving Inc. densified soil to prevent liquefaction in a quake, using the standard stone column method. Columns had to be placed around obstructions and future pile locations. Vancouver Pile Driving then installed the 1-m-dia steel piles, from 13 m to 53 m long. For 60% of the foundation, grade was cut down to mean tide level, which resulted in about 2 m of exposed pile at the top. The rest of the piles are exposed to water as deep as 20 m.
Beneath the grid of exhibit-hall columns, piles are on a regular grid. Otherwise, pile locations were governed by loads from steel columns “all over the map,” says MacPherson. “Remarkably, piling went fairly well,” he adds. Even with unforeseen obstructions, there were problems with fewer than a dozen, he says.
The north section of the deck was erected using barge-mounted cranes, as was the marine piling, the habitat apron and some structural steel. One strategy was to minimize site-cast concrete: Pile caps were cast in place but precast concrete deck slabs span between them. Concrete topping finishes the deck.
The basement-less deck has a watertight 3-m-deep x 4-m-wide utility tunnel to feed the exhibit-hall floor, running 250 m east to west, below the water line. After the foundation was done, crews from precaster Surespan Construction Ltd.’s local office dropped in segmented and post-tensioned tunnel sections. It is covered by a cast lid, monolithic with the deck.
In hindsight, MacPherson says he would have pushed harder for more regularity in superstructure columns, which would have optimized deck construction. For example, the engineer estimates the 300 types of precast deck, with different lengths, reinforcing patterns and widths, could have been cut to 150 with more regular columns. MacPherson says it is penny-wise and pound foolish to focus on minimizing steel weight at the expense of increasing construction complexity.
Walker calls the steel structure “a bit of a challenge,” and the structural engineer agrees. “This is our first full-scale convention center,” says Simpson. “I think we took on one of the more difficult ones, and we’ve had a great success.”
The steel superstructure “makes your eyes go funny, it’s so busy,” says Simpson. “But fundamentally, it is dead simple engineering-wise. We got a great cost of structure in the building,” landing within 5% of the original weight estimate.
Dozens of large-format wall trusses, scattered eccentric-braced bays, which minimize steel weight, and floor beams take lateral loads. One ballroom wall truss is more than 22 m deep. “It is better to have widely distributed seismic yielding systems because it provides excellent redundancy,” says the engineer.
The architecture also complicated the frame. The north face and its columns slope to the north, placing a lateral push on the building, a push the structure needs to resist. “We had to find a system that would resolve the forces and still allow the building to go through reverse cyclic yielding” in a quake, says Simpson.
One way to do this is to add steel weight. Instead, the engineer used a series of diagonal tensioned braces with disk springs. The spring is tensioned to match the diagonal push of the gravity force of the leaning column, says Simpson.
The approach, which allows serial yielding in a major seismic event, is more common to nuclear powerplants and mechanical systems. “I believe this is a transfer of technology,” says Simpson.
For the interstitial parking level, the engineer designed long-span trusses with diagonal-free Vierendeel sections between braced frames. Vierendeels allow cars to drive through the trusses.
The living roof presented another engineering challenge, says Simpson. The entire roof’s dead weight is 20 million lb. Of this, 12 million lb is the weight of the growing medium, which was installed at 8 in. deep and compressed to 6 in. Each additional inch of growing medium adds $495,000 to the cost of the structure to support the roof, says the engineer. Also, the multistory impact of the roof load substantially increased seismic loading.
With three sides of the site not accessible and the deck work area limited to three crane runways, conditions for steel erection were “not ideal,” says Canron’s McLagan.
Canron’s contract was $74 million. McLagan estimates the cost was 20% higher than a typical convention center. The job has 17,500 tons of steel, and there were 21,248 unique pieces to erect individually, including 200 truss sections, many more than 7 m deep.
On the deck runways, Canron had two 230-ton crawler cranes and a tower crane on rails with a 44-ton lifting capacity. That limited the size and weight of picks. “Very often, we had truss sections going up in pieces,” says McLagan, which translated to 50% more time for field-welding. “That made it harder,” he adds.
Piecemeal construction and complex geometry, with few horizontal or vertical surfaces and many sloping members, translated to a frame that was largely not self-supporting during construction. There was much falsework—some towers were as tall as 8 m—that had to be moved around the site.
The north sloping columns were especially tricky. Canron used tiebacks into the building to keep them from falling over.
Steel erection started at the end of October 2006 and finished last June. Early on, Canron had to contend with raw-steel price escalation. To try to get some control, the fabricator bought two-thirds of the tonnage during the job’s first phase. “When we got to the second phase, prices had gone up,” says McLagan. The strategy saved $2 million.
Steel building information modeling helped ease the frame work. Paper drawings were used as the basis for the steel contract, but Glotman Simpson built a 3D model using Tekla Structures and other analysis software. Once the model was “comfortably complete,” a copy was issued to Dowco Consultants Ltd., Canron’s Burnaby, British Columbia-based connection detailer, says Sanjay Prasad, Dowco’s CAD development manager.
Dowco started preparatory work in its Tekla model while the engineer continued to finalize its model, says Prasad. When necessary, the engineer issued partially updated models to accommodate design changes so that Canron could complete connection design. “These changes copied into our live model,” says Prasad.
Changes also came on sketches and in other ways, says McLagan. Dowco kept updating its model, and soon there were two master models—the engineer’s and the fabricator’s, says Prasad.
The engineer reviewed and approved pieces of the fabricator’s 3D model, not shop drawings on paper. Dowco then produced paper shop drawings from the approved model for use in fabrication and erection.
The Dowco model also was used to run Canron’s computer numerically controlled cutting equipment and the model was sent to the architect for drawing coordination.
The structural engineer says BIM was a big help in monitoring steel quantities. “BIM also keeps the owner informed, encouraging a transparent system between the owner, fabricator and engineer,” says Simpson.
“We tried to do unique” things with BIM, VCCEP’s Walker says. “I think it did work but it could be better.”
He declines to be more specific about BIM lessons or others learned on the project, saying it would be premature. “We will have our lessons-learned session in another two or three months, after the project is complete,” Walker says.