MILWAUKEE, Wisconsin – Burgess & Niple (B&N) bridge engineer Mike Seal is glad a baseball game won't be underway when his team of inspectors from the Columbus, Ohio-based architectural and engineering firm completes its work at Miller Park in Milwaukee. He won't be tempted, he said, to comment on the judgment of the umpires from his perch 300 feet above the playing field.
Instead, Seal and the B&N team will be focused on their inspection work, tethered to the complex trusses and box chords that form the moveable roof at the five-year-old stadium, which is the home of the Milwaukee Brewers. Under a five-year contract with the Southeast Wisconsin Professional Baseball Park District, B&N will conduct its initial inspection in July during Major League Baseball's All-Star Game break.
"This is different from a bridge inspection because the structure is moveable and is part of a building," said Seal. "The roof, of course, is still subject to the same forces and stress that any structure is subjected to. As an engineer, this is a unique and exciting project for us to do. We supply a good service and our climbing techniques are well-suited to the baseball district's needs."
To perform the arm's length inspection, each B&N engineer will use adapted rock climbing and industrial rope access techniques that allow them to detect and document subtle deficiencies that would not be apparent to someone in a mechanical bucket, even if they could access the roof structure. Inspectors also will check for paint loss and corrosion, as well as perform magnetic particle testing for weld integrity. B&N engineers use the same techniques during bridge inspections to avoid expensive lane closures and equipment rental.
The same rope climbing techniques B&N will use in Milwaukee were used in similar stadium inspections conducted by the company in Cincinnati; Ithaca, N.Y.; and Morgantown, W.Va.
Dead loads on the 600-foot span sections of the Miller Park roof are comparable to those on a similarly sized bridge. The firm's engineers have extensive experience with large bridges, having inspected nearly 50 spans of 600 feet or more. B&N's contract calls for a structural inspection of the moveable and fixed-roof trusses and their supporting elements, focusing on the high-stress truss members, tension cables, and welded and bolted connections. In addition, the engineers will develop a database used to monitor performance of the facility by tracking maintenance, structural conditions, inspection frequencies and findings, and other important items.
The 10.5-acre roof consists of seven, pie-shaped panels. Five of them rotate on a pivot behind home plate. When opened, the moveable panels nest within the fixed panels along the first- and third-base lines. The huge structure—built with nearly 13,000 tons of structural steel—can open or close in just 10 minutes.