Hanson Structural Precast of Maple Grove, Minn., has added to its 2014-15 schedule more than 102,000 linear feet of precast concrete members to support seating sections for the new Minneapolis home of the National Football League’s Minnesota Vikings.
Owing to a wealth of stadium experience, an innovative production technique and unique vacuum riser-lifting system—first deployed on the Minnesota Twins’ Target Field, Hanson Structural Precast plant was selected to produce quality-finished stadia risers for the Vikings venue. In addition, it will produce precast concrete beams, columns, raker beams, spandrels, stair units, and interior structural wall panels.
Ground was broken in late December for the new stadium. Designed as a stunning world-class stadium, the impressive structure will feature a soaring, ship-like prow dramatically pointing upward and surrounded by high-tech glass walls, a trellis-like glass roof, and 95-ft.-tall, pivoting glass entry doors. But the “guts” of the landmark new stadium will be a precast concrete bowl cradling seating sections and supporting tens of thousands of fans and spectators.
“For the Viking stadium, the architects originally designed the project to utilize double and triple concrete risers,” says Steve Olson, Hanson sale representative. “But when we showed them our other stadium work, they quickly approved our plan to use single risers and the vacuum-lift technology due to their great advantages.”
Most producers, Olson explains, fabricate double risers, face up and then broom-finish the surface manually, which can vary in consistency. Hanson pours single risers face down with a consistent, form-liner finish on the critical surface. This also ensures that the harder, more consolidated concrete is on the face of the risers.
By producing single risers, rather than double or triple risers, Hanson will also be able to better control the quality of the jointing, provide more accurate alignment, and erect the components using a vacuum lift system. This will also reduce costs. Since Hanson already has single riser forms it will not have to purchase new double and triple forms.
The innovative lifting devices hang from a crane and use suction from a vacuum reservoir to life precast components from their forms, rotate and finish them in the plant, and then lift and place them in the field. Double or triple riser units would require lifting by traditional rigging which would result in the need for extensive patching at the lifting inserts.