At one time, when people thought of Sears, they thought of the Sears catalog – a 3-inch-thick “Consumers' Bible” offering almost anything and everything under the sun. In 1973, the Sears brand acquired a new symbol, the 110-story Sears Tower. The tallest building in the world, its roof topped out at 1,450 feet. With 4.5 million square feet of floorspace within the two-city-block footprint, it would take 29,615,797 Sears catalogs to fill it up.
Building such a tall structure is some serious work. Interestingly though, the biggest challenges on this project didn’t revolve around building height, but around the fact that street-level space was minimal. Consider that the building, renamed the Willis Tower in 2009, weighed 222,500 tons. How could planners and workers navigate busy Chicago streets to get 222,500 tons of stuff to the site without even a staging area nearby? Add the equipment, supplies and as many as 1,800 workers onsite, and logistics could have been a nightmare. But planning and expertise paid off, as the fast-track project was completed in less than three years. Credit goes to many on this project, including the design-build team, which included Morse Diesel as construction manager and general contractor, and Skidmore, Owings and Merrill (SOM) as architect. SOM came up with a bundled-tube design – nine attached tubes would rise to various heights, resulting in setbacks to provide myriad floor plans as well as an abundance of windowed office space. The variety would appeal to potential tenants on upper floors while Sears occupied the larger, uniform lower levels.
One way to minimize site logistics was to do as much as possible offsite. The structural-steel phase of construction offered a prime example of meeting the logistical challenge. American Bridge Co. was responsible for fabricating and erecting the 76,000 tons of steel to form the building’s skeleton, and attacked the challenge with gusto.
The erector-set design and construction of the Sears Tower’s steel superstructure enabled steel columns and floor spandrels, along with needed flanges, holes and other add-ons, to be fabricated and attached at American Bridge’s Gary, Ind., location, about 35 miles away from the site. Once completed, the fabrications – workers called them Christmas trees – were loaded onto modified flat-bed trucks for just-in-time delivery, where crews immediately installed the columns and spandrels to propel the Sears Tower skyward.
Lincoln Electric was there through it all, as a partner on a construction project that required 268,000 major welds to augment insertion of 740,000 high-strength bolts. Jim Rosenthal, retired district sales manager, had developed a close relationship with American Bridge before and during this project; “so much so that I had an inbox there,” he recalls. The closeness manifested itself in many ways, with Rosenthal able to suggest fabrication improvements and help develop equipment and procedures to assist in the structural-steel work.
For this project, Lincoln Electric provided wire for the consumable-guide electroslag welding performed at American Bridge. It also supplied wire for welding pipes to holes in floor-spandrel webs and to weld floor spandrels to column flanges. On the job site, Lincoln Electric wire again got the call – 120,000 pounds worth of consumables - to weld flanges from column to column.
Onsite, 30-35 welders worked their way up the structure to attach the columns, sometimes straddling in relative comfort across girders, and at other times dangling off of the side of the building in harnesses. Where they sat definitely had an effect on work speed.
“Whether the workers rested on girders or hung on slings, the welds to be performed were exactly the same,” notes Carl Occhialini, a Lincoln Electric technical representative who joined the project in its latter stages and has since given presentations on construction of the building, using information from Rosenthal. “But timing studies showed that the welding was performed 10 percent faster on the slings.”
Welding equipment and power supplies ran up the building-envelope’s exterior – a simpler method than trying to snake it up through the building’s core. Making travel easier, Lincoln Electric’s wire feeders provided a large welding radius – more than 50 feet. With this setup, welders didn’t have to lug 50-pound wire coils across the beams and decks to perform various welds.
On a cold, blustery May day, structural-steel erection ended with a topping-off ceremony, where ironworkers, unwilling to let winds delay the event, placed the final beam. Its 12,000 signatures – project workers, designers, Sears employees and Chicagoans – denoted not only completion of the superstructure phase, but also symbolized the cooperation so necessary to completing the massive project.
“As the project developed and everyone realized that this would be a special building,” says John Zils, a young engineer with SOM at the time, “a team effort really developed across the design firms and also with the construction teams. I look back and marvel at the strength of the camaraderie.
“The Willis Tower,” he continues, “will always be a Chicago icon, no matter how many buildings are taller. When I talk to people around the world, it is the one building that people recognize, and it still has that special feeling.”
On the job during construction of many Chicago skyscrapers in the late-1960s and early-‘70s, Rosenthal often chose to straddle a beam and scoot across rather than walk it. The dizzying heights of buildings such as the Willis Tower give him an appreciation for those who perform the work day in and day out, and also give him the statistic of which he is most proud.
“On a structure this tall, and with the amount of potential danger, this project had no deaths or major injuries,” he says. “I think about that – how the safety plan was developed and how it was executed by the experienced superintendents and ironworkers.”
It sways as much as 10 feet at the top, and actually leans away from the sun due to heat that expands the metal, but for all intents and purposes, the Willis Tower is a rock. The massive Chicago landmark was born as the tallest, and lives as a solid symbol of what people, backed by the finest knowhow and the finest machinery, can do.