Gigantic steel tower erected to hold up 44-million-pound iconic New Arena roof
By: Bob Condor
SEATTLE — Just a few days after NHL Seattle introduced Ron Francis as the team’s first general manager, the New Arena at Seattle Center was marking its own “big milestone” on July 23.
“Into the center of the roof, we erected what’s called a shoring tower with four steel legs,” explains Ken Johnsen, construction executive for Oak View Group and NHL Seattle. “It goes smack into the roof. We put it tight, then [the construction crew] jacks it up real tight. It allows us to now take away [demolish] the remaining 20 percent of the concrete bowl.
That concrete bowl, once the base of the stands, has been helping to support the landmark roof of the New Arena. The finishing touches of the concrete bowl demolition started this week. When finished, there will be nothing left inside the former arena.
It’s a brand-new arena from here on down.
The roof will be held up by the central shoring tower plus an additional 72 inner and outer temporary steel columns.
“It’s amazing,” said Johnsen. “The engineers calculate how much the roof goes up when they start jacking the [central] tower into place onto the roof. You want to make it tight but not raise the roof, just hold it. The engineers projected the roof would go up an inch and settle at about a quarter-inch. It went up an inch and settled at an eighth-inch, so it was perfect.”
Forty of the temporary steel columns will become 20 pairs connected by steel crossbeams positioned proximate to where 20 corresponding “Y” supports currently stand. The remaining 32 temporary support columns will be in groups of eight and matched proximate to where four major buttresses currently stand.
Each temporary column requires power-drilling a 70-foot hole, which involves screwing downward and pulling up gigantic spirals of dirt to the surface, then shaking the dirt free into enormous piles scooped into dump trucks by bulldozers. Any kid who loves trucks would be mesmerized.
Once all of the temporary columns are complete-ringing the central tower on all sides–the arena construction will move to the excavation phase. Six hundred thousand cubic yards will be dug and hauled away during the next few months as the arena footprint significantly widens in all subterranean directions and the arena floor drops 15 feet lower.
The central tower was effectively erected in one day, with help from a 180-foot crane and workers clearly not intimidated by heights. The workers were on a high-up platform making sure the tower pieces all fit snugly and securely.
The central tower and temporary columns represent significantly more than enough reinforcement to hold up the 44-million-pound roof during the subterranean construction.
“Once all of the [arena] construction is in place, it will be unbelievably secure,” says Johnsen. “But you have to make sure during all stages of construction is just as safe and just as safe in dealing with seismic concerns. We have to keep it that way while we are building it, we need to be able to say at any point during construction if an earthquake hits, we’d be happy to be in the arena.”
It’s all part of the “critical stage of getting ready for excavation,” said Johnsen, adding the dig will go as deep as 70 feet at perimeter areas of the rectangular hole.
“When the last excavation was done in 1995, they dug in a V-shape,” said Johnsen. “We are going much wider all around and doubling the [square footage] of the arena.”