FULL SWING
PR A NOG EW E R H I T T E R RS’ ROLLING ROOF BY ERIN PINKERTON
The roof of Globe Life Field is 5.5 acres — or 240,836 square feet — and it rolls all at once. It’s the largest single-panel operable roof in the world, and its construction required 19,000 tons of structural steel, a top-notch construction team and the world’s largest American-made conventional crawler crane to put it all together. Other major sports stadiums have movable roofs, but many have multiple panels. Globe Life Field has only one. “The one panel operable roof structure has a continuous seal system around the perimeter. The bulb seal on the east and west are under compression while the flap seal on the north and south allow for movement in the structure,” said Telissa Hubbard, assistant project manager at Manhattan Construction. “The roof seal is a critical part of a building with this design.” When the roof is closed, the outdoor elements are kept at bay by a white rubber membrane on the north and south sloped planes, and the flat center is covered with clear panels made of ETFE (ethylene tetrafluoroethylene). Donald Veitenheimer, structural superintendent at Manhattan Construction, described ETFE as resembling a moon bounce, two pieces of plastic with air blown in between. “It has this new aspect called intelligent shading,” added Grant Phifer, senior project engineer at Manhattan Construction. “When the pillows blow up, they get air sent through them, and the foil inside separates to create a gap. If you’re looking directly underneath, it blocks the sunlight, so sunlight comes in only at a certain angle.” The roof structure consists of five huge pairs of steel trusses and tie-in steel between each truss, and the roof can open in about 12 to 15 minutes so Texas Rangers fans can enjoy the ballgame under the shining springtime sun.
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“The operable roof consists of 10 trusses, which were erected in pairs and are supported by the north and south rails. The roof actually rolls on a rail similar to a railroad track,” Hubbard explained. “Once the system is complete, 10 motors will operate the roof.” Under all the innovative roofing materials and powerful mechanization, there is steel — lots and lots of steel. In all, the roof steel weighs about 19,000 tons, Phifer said. That’s about 38 million pounds. The steel was furnished and fabricated by W&W/AFCO Steel and erected by W&W Steel Erectors. The structural steel was brought in and assembled on-site in the stadium bowl. Each of the roof ’s 33 steel truss sections were erected in three parts: the north section, the middle section and the south section. After one truss was completely erected, it was slid down the rail to the west so the next truss could be set. Once the first and second trusses were completely erected, they were tied together with more steel. Moving this much steel required many work hours and enormous equipment. “We had up to 11 cranes on-site at a given time,” said Charles Dougherty, president of W&W Steel Erectors. “The main heavy-lift crane that we used to erect the roof truss assemblies was a Manitowoc 31000 heavy-lift crane, and it is the largest crawler crane manufactured in the United States.” The Manitowoc 31000 was positioned in the stadium bowl so crews could assemble and
