This is part two of a series on how 3D model-based design and materials quantity take-off enabled the restoration of Wrigley Field in Chicago. See part one if you missed it.
Steel Fabrication and Erection
The structural design of Wrigley Field’s bleachers maintains the historic nature of the ballpark and presents some unique challenges for fabrication and erection. The design’s connections, column sizes and thicknesses required a complex fabrication, welding and installation plan.
Lenex Steel of Indianapolis developed a 3D model for the fabrication, which took between 16,000 and 17,000 man-hours to complete the project. It required three different production foundries to supply the volume.
Most of the steel came from supplier Steel Dynamics, Inc., which shipped its rough beams and long products from its facility in Jeffersonville, Ind., directly to Lenex for fabrication or to the site.
After analyzing the 3D model, the team confirmed that structural supports could be prefabricated offsite and installed, essentially, like a large erector set. “Kudos to the steel fabricator for seeing that early and getting almost all of that welding done in the shop,” said Kevin Heatter, project executive at general contractor Pepper Construction.Each morning, Pepper would receive confirmation of what steel members they would receive from Lenex in Indianapolis. Each trip was typically 3 or 4 hours so the riggers could plan their afternoons around what would arrive in a few hours, depending on the weather.
Lenex also had a steel yard on the city’s south side that they utilized as a staging area to store steel members not yet ready for installation. During the off-season, the back half of Wrigley Field’s Green Lot was used as a staging area for lay-down of arriving materials that sub-contractors still had to inspect or work on before installation.
“We never had more than a few trucks here because you don’t want to have materials you’re not ready for yet,” Heatter said. “Wrigleyville is a very dense area so we wanted to have no more than two or three days of steel ready for installation.”
In Time Delivery
When they arrived, the steel was taken off the crane, set in place and shored up from below. This just-in-time prefabrication and delivery process had a tremendous impact on expediting the schedule and lowering costs.
For erector Danny’s Construction that meant receiving and installing large pieces of structural steel with tight tolerances nearly every day.
Overall, 880 tons of steel were installed in the outfield. “That is a lot of tonnage for a relatively small area and the geometry makes it more complex,” Heatter said. “The steel fabricator and the erector in the field did a great job.”
More on the steel story at Wrigley Field tomorrow. Follow Jeff Yoders on twitter at @jyoders19.