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3 days, 5,600 tons; Cards Stadium about to get its cover
Pat Flannery
The Arizona Republic
Feb. 18, 2005 12:00 AM
The "gee whiz" moment in the building of Cardinals Stadium occurs this weekend when 120 engineers, steel workers and specialized equipment operators finally put a lid on the $370.6 million venue.
Mammoet, a Dutch company specializing in heavy lifts, will fire up its high-tech gadgets this morning, kicking off a carefully choreographed three-day operation to hoist the stadium's 5,600-ton retractable roof structure - that's 11.2 million pounds of steel - into place high above the field.
"We believe it's the heaviest lift ever in North America," said Brad Parker, an Arizona Sports and Tourism Authority spokesman.
The lift is another milestone in the stadium's development. Once the roof is finished and sealed later this year, work will migrate inside and passers-by on Loop 101 won't notice the changing construction landscape nearly as often as they once did. The stadium should be weatherproof by November.
Despite an unusually wet winter, construction is still on schedule for the stadium to open in August 2006. Rain this weekend should not deter the lift, though it could be delayed if high winds or lightning are present.
Designers planned for this weekend's lift for several years, building four concrete supercolumns into the bowl specifically to bear the weight of the lift and hold the roof's gigantic trusses in place until the rest of the roof-support system is in place.
Even the stadium bowl was built in sections like a pie, rather than by the usual level-at-a-time circular method, to accommodate the trusses. The unusual construction method freed up space inside the stadium so the trusses could be built there, near ground level, instead of high above the bowl.
Construction manager Charlie Prewitt of Hunt Construction Group said piecing together the roof's skeleton in this way was safer, easier and cheaper, and it happened sooner than otherwise would have been possible. Now, it has to be lifted into place.
Its central features are two 700-foot-long Brunel trusses that were assembled section by section starting last August. The length of three Boeing 747 jets parked end to end, these jumbo eye-shaped trusses weigh 1,770 tons apiece and had their tapered ends built into vertical slots in the concrete supercolumns that will help support them. Retractable roof panels are now attached securely atop the parallel arcs, stabilizing them for the lift.
Each 12- by 17.5-foot supercolumn has a yellow steel frame atop it that houses two all-important strand jacks. The frames are easily visible to cars passing on Loop 101.
Through each jack are threaded 54 steel cables, or "strands," that extend down through the slot in the supercolumn and attach to the end of a Brunel truss. That means each end of a Brunel truss will have two jacks and 108 cables pulling it upward through the slot toward the jacks.
For today's initial liftoff, the Brunel trusses will be unbolted from steel support posts and guy lines propping them up on the field. The hydraulic jacks, synchronized by computer and operated from a control center on the upper concourse, then will take a small stroke.
Prewitt said the roof assembly initially will move just a few inches at a time. Then engineers will inspect, making sure everything is A-OK. The process will continue that way until the belly of each truss, the lowest point in its arc, clears support posts underneath.
"It's going to be like watching grass grow," Prewitt said. "The first couple of inches, it could take us an hour."
As their ends are pulled, the heavy trusses will flex like a hunting bow. Prewitt therefore estimates the jacks will have to lift the ends 6 to 7 feet before the belly of either truss clears its support posts. Once airborne, the trusses will be raised 1 1/2 more feet and left to hang under their own weight until 8 a.m. Saturday, when the real lifting begins.
Again, the jacks initially will take small strokes, with engineers making sure they are pulling at equal rates and keeping the hoisted steel level.
When engineers are confident everything is working as planned, the jacks will take increasingly large strokes until the roof is slowly rising 12 to 18 inches per stroke. The routine will stop periodically for inspections and laser measurements as engineers pore over computer data monitoring stress on the jacks, trusses and supercolumns. The concrete columns, for example, will bow slightly under the load's weight.
Seven to nine hours later, if all goes well, the roof will be at its highest point. The jacks will stop, and the roof again will hang overnight. On Sunday, workers will scale scaffolds around the supercolumns and maneuver four horizontal transfer girders into notches near the tops of the columns, bolting them in place. The roof then will be lowered a foot or two, bringing the ends of the Brunel trusses to rest atop the transfer girders.
Once the trusses settle into place, work will start in March to link smaller trusses from the top edge of the stadium bowl to the Brunel trusses. Those smaller trusses will support the rest of the roof's metal and rubberized decking.
When structural roof work is finished in late June, a tough, specialized fabric known as Birdair will be stretched over the skeletal frames of the retractable panels and other parts of the roof. In late fall, the retractable panels will open for the first time.
As complicated as the process seems, Prewitt said, it is one of Mammoet's simpler jobs.
"It's real amazing," Prewitt said. "When you think about it, this is about as simple a lift as you can do because you're taking it straight up."
AzCentral.com
Pat Flannery
The Arizona Republic
Feb. 18, 2005 12:00 AM
The "gee whiz" moment in the building of Cardinals Stadium occurs this weekend when 120 engineers, steel workers and specialized equipment operators finally put a lid on the $370.6 million venue.
Mammoet, a Dutch company specializing in heavy lifts, will fire up its high-tech gadgets this morning, kicking off a carefully choreographed three-day operation to hoist the stadium's 5,600-ton retractable roof structure - that's 11.2 million pounds of steel - into place high above the field.
"We believe it's the heaviest lift ever in North America," said Brad Parker, an Arizona Sports and Tourism Authority spokesman.
The lift is another milestone in the stadium's development. Once the roof is finished and sealed later this year, work will migrate inside and passers-by on Loop 101 won't notice the changing construction landscape nearly as often as they once did. The stadium should be weatherproof by November.
Despite an unusually wet winter, construction is still on schedule for the stadium to open in August 2006. Rain this weekend should not deter the lift, though it could be delayed if high winds or lightning are present.
Designers planned for this weekend's lift for several years, building four concrete supercolumns into the bowl specifically to bear the weight of the lift and hold the roof's gigantic trusses in place until the rest of the roof-support system is in place.
Even the stadium bowl was built in sections like a pie, rather than by the usual level-at-a-time circular method, to accommodate the trusses. The unusual construction method freed up space inside the stadium so the trusses could be built there, near ground level, instead of high above the bowl.
Construction manager Charlie Prewitt of Hunt Construction Group said piecing together the roof's skeleton in this way was safer, easier and cheaper, and it happened sooner than otherwise would have been possible. Now, it has to be lifted into place.
Its central features are two 700-foot-long Brunel trusses that were assembled section by section starting last August. The length of three Boeing 747 jets parked end to end, these jumbo eye-shaped trusses weigh 1,770 tons apiece and had their tapered ends built into vertical slots in the concrete supercolumns that will help support them. Retractable roof panels are now attached securely atop the parallel arcs, stabilizing them for the lift.
Each 12- by 17.5-foot supercolumn has a yellow steel frame atop it that houses two all-important strand jacks. The frames are easily visible to cars passing on Loop 101.
Through each jack are threaded 54 steel cables, or "strands," that extend down through the slot in the supercolumn and attach to the end of a Brunel truss. That means each end of a Brunel truss will have two jacks and 108 cables pulling it upward through the slot toward the jacks.
For today's initial liftoff, the Brunel trusses will be unbolted from steel support posts and guy lines propping them up on the field. The hydraulic jacks, synchronized by computer and operated from a control center on the upper concourse, then will take a small stroke.
Prewitt said the roof assembly initially will move just a few inches at a time. Then engineers will inspect, making sure everything is A-OK. The process will continue that way until the belly of each truss, the lowest point in its arc, clears support posts underneath.
"It's going to be like watching grass grow," Prewitt said. "The first couple of inches, it could take us an hour."
As their ends are pulled, the heavy trusses will flex like a hunting bow. Prewitt therefore estimates the jacks will have to lift the ends 6 to 7 feet before the belly of either truss clears its support posts. Once airborne, the trusses will be raised 1 1/2 more feet and left to hang under their own weight until 8 a.m. Saturday, when the real lifting begins.
Again, the jacks initially will take small strokes, with engineers making sure they are pulling at equal rates and keeping the hoisted steel level.
When engineers are confident everything is working as planned, the jacks will take increasingly large strokes until the roof is slowly rising 12 to 18 inches per stroke. The routine will stop periodically for inspections and laser measurements as engineers pore over computer data monitoring stress on the jacks, trusses and supercolumns. The concrete columns, for example, will bow slightly under the load's weight.
Seven to nine hours later, if all goes well, the roof will be at its highest point. The jacks will stop, and the roof again will hang overnight. On Sunday, workers will scale scaffolds around the supercolumns and maneuver four horizontal transfer girders into notches near the tops of the columns, bolting them in place. The roof then will be lowered a foot or two, bringing the ends of the Brunel trusses to rest atop the transfer girders.
Once the trusses settle into place, work will start in March to link smaller trusses from the top edge of the stadium bowl to the Brunel trusses. Those smaller trusses will support the rest of the roof's metal and rubberized decking.
When structural roof work is finished in late June, a tough, specialized fabric known as Birdair will be stretched over the skeletal frames of the retractable panels and other parts of the roof. In late fall, the retractable panels will open for the first time.
As complicated as the process seems, Prewitt said, it is one of Mammoet's simpler jobs.
"It's real amazing," Prewitt said. "When you think about it, this is about as simple a lift as you can do because you're taking it straight up."
AzCentral.com
