Repairing retractable roof proves to be major undertaking

It is not everyday contractors move a 12,000-ton retractable baseball stadium roof, but that is just what a team of laborers were called to do last September when all of the bogies responsible for opening and closing the Milwaukee Brewers’ stadium roof needed to be replaced before the start of the season on April 1.

The Miller Park roof, which is similar to a fan, has five panels. Three of the panels open to the left field side and the other two panels open to the right field side. Each panel is stacked at a different elevation, so when they are opened, they rest on top of one another. The bogie assemblies roll on a common track for every panel, with a separate rail for each panel.

“There had been a number of issues since the installation of the original Toblerone frame,” says Jim Ronning, the consulting engineer for the project. “This roller frame sits atop the bogies and it expands and contracts to allow movement between the bogie and the roof panel.”

Ronning says about five years after the park opened in 2001, noticeable problems surfaced as the Toblerone roller bearings and bogie wheel bearings began wearing out. The bearings were grinding against the track as they were under too much stress.
“The goal was to get a system that had considerably more capacity to reduce the track’s stress levels,” he says.

Enerpac Integrated Solutions, supplier of hydraulic jacking equipment, began the process by gathering quick disconnect couplers and fittings, jacks, hydraulic pumps and hoses, which they then preassembled for the contractors. After Enerpac assembled the equipment at its facility, Ronning, who was in charge of making specifications for the jacking arrangements, enlisted the help of laborers to prepare the roof.

Four jacks total were needed to lift the roof. Ronning and his crew jacked each panel 6 to 8 inches above the bogie so it could be removed. “Once the roof was raised in a certain lifting spot, the bogie was simply rolled out and a new bogie was rolled in,” Ronning says.

Price Erecting, a company specializing in rigging and erecting services, also aided in the difficult task of raising the roof so the bogies could be replaced by providing a crane. “Once the commitment was made to jack the roof panel and install new bogies, a crane was set up outside the stadium on the outfield side to change and replace new bogies,” Ronning says.

A new system, requiring the bogies to have four wheels instead of two, was installed to cut the track bearing load in half. In all, 10 bogie wheels were replaced. Each change out operation spanned one day and every lifting spot had to be prepped at least three to five days ahead of time.

The total cost of repairing the roof is estimated at $13 to $15 million.