|Accessible. High-reach lifts got workers in tight spots. |
(Photo courtesy of MC4West LLC )
When it bid steel erection on the McCormick Place expansion, Shakopee, Minn.-based Danny’s Construction Co. Inc. proposed an unusual combination of access equipment that its engineers believed would dramatically improve the ironworkers’ ability to move quickly and safely on the tightly scheduled project.
As it turns out, the firm’s novel scheme of rolling scaffolds, falsework and mobile aerial devices caught the attention of project executives and local safety inspectors. ”It brought a whole new awareness of safety,” says Katie Twomey, vice president for design-builder Mc4West and Bethesda, Md.-based Clark Construction Group.
On the building’s third floor, where the 100,000-sq-ft ballroom and 475,000-sq-ft exhibit hall sits, Danny’s set up rail-mounted scaffolds “on steroids,” as Gary H. Schalmo, Mc4West project director, calls them. Workers detailed structural members from the scaffolds, rather than “walking” the frame, and used them to install the project’s 120 to 180-ft-long roof trusses. Atop the 60-ft-long, 45-ft-wide and 40-ft-tall scaffolds were metal decks that served as giant work platforms. “It saved us from putting up nets everywhere,” says Bill Hanson, Danny’s vice president.
The firm’s engineers also designed falsework that cut down dangerous lifts and freed up cranes on site to do more work. Several heavy trusses were lifted in one piece, such as a 105-ft-long, 22-ft-tall and 22-ft-deep box truss supporting the 60-ft cantilevered end of the central concourse. But most were spliced to cut down “critical” lifts—risky maneuvers that require cranes to operate at more than 75% of their rated capacity.
Danny’s used one crane to lift each truss section, securing one side to a steel megacolumn and the other side to a 75-ft-tall falsework tower. Capable of holding 200 kips, each tower held a 15-ton chain fall that allowed crews to adjust the vertical alignment of truss members in “minutes instead of hours,” says Hanson.
Danny’s also rented a forest of 125 and 135-ft-tall boom lifts that provided access to tight spots, such as the concourse’s high roof. According to Jerry Lodovisi, area sales manager for Lemont, Ill.-based supplier Illini Hi-Reach Inc., nearly every machine included an onboard electric generator with 250-amp capacity for light welding. JLG Industries Inc., McConnellsburg, Pa., rolled out the “SkyWelder” package five years ago.
The lifts typically rent for $9,000 to $12,000 per month. But Hanson says they pay for themselves by adding speed and safety.