Once the steel tube bending or steel plate rolling is completed by a Bender/Roller or Rolling House (a company that specializes in curving steel sections), it is typically shipped to a structural steel fabricator who trim cuts the rough-cut, curved sections to length, welds on end plates, and punches holes for bolting the assemblies together in the field. Once the fabrication is completed, the assemblies are shipped to the job site where they are erected as the final steel structure.
Steel erectors often face difficult challenges. Here are some examples:
Two 250-ton crawler cranes operating up to 95% of their capacity performed a tandem lift to place a 228-ft long pedestrian bridge for the Tempe Town project in Arizona.
To install the 200-ft span across Monroe Street connecting Chicago’s Millennium Park with the Art Institute of Chicago, a crane was placed on a lower-level busway. It took three to four months to plan the three-hour lift of the 110,000lb section.
Like the Nichols Bridgeway, the Pritzker Pavilion is built above a parking lot, rail lines, and a lower level busway. Consequently, weight considerations became primary. Furthermore, heavy steel sections require heavy machinery to pick and place the units—all of which further complicates the erection issues.
The red crane in the picture above had to be disassembled on Columbus Drive (the road on the right side of the picture), lifted onto a mat that would transfer the load to the reinforced columns of the parking lot below, and then reassembled. The yellow pipes of the trellis were supported by 78-ft-tall green shoring towers until they were welded together.
Construction constraints dictated that the trellis be built simultaneously from each end of the pavilion. But it still fit up perfectly.
Early collaboration on the part of the architects, engineers, bender/roller, fabricator and erector contributes to the successful erection of complex structures.