Putzmeister Clamp-Down Mounting Base Speeds Construction of Chicago High-Rise
Putzmeister Clamp-Down Mounting Base Speeds Construction of Chicago High-RiseSTURTEVANT, Wis. (June 4, 2004) – A new, highly efficient method of placing concrete is being used in the construction of Lancaster, a high-rise residential complex in the new Lakeshore East development within Chicago’s famous Loop district.
Rather than continuously raising a placing boom tower as a building’s skeleton reaches skyward, general contractor James McHugh Construction has chosen a custom-designed Putzmeister clamp-down mounting base to work in conjunction with a self-climbing form system. The base conveniently becomes a part of the framework and rides with the system as it is raised hydraulically within the building’s core. Because the base is not independently connected to any tower, it moves with the forms, realizing substantial time savings.
Initial assembly of this system was less involved than with traditional methods because the base was simply clamped down to structural beams. The beams were reinforced to handle a load factor of 48,000-lbs., which was needed to absorb reaction forces of the 18,000-lb MXR 34/38 placing boom and its pedestal, when at a full 111-foot horizontal extension.
“With the clamp-down base, we can work within an easy three-day schedule for each floor,” said Ken Hoyle, project superintendent. “And with this mounting design, we eliminated an entire step in raising the base and that helps save a day overall.
“Even if it rains for half a day or another problem occurs, we still have enough time to absorb any minor delays without affecting the cycle.”
Putzmeister developed the special mounting base at McHugh’s request. McHugh, which regularly appears on the nation’s Top 400 Contractors’ list, was searching for a different method of constructing the 30-story building. Successful use of the Putzmeister base is making the McHugh team take another look at how all high-rise structures should be constructed, including smaller, 18-story buildings where use of a placing boom has been considered impractical.
McHugh Construction is a family-owned organization established in 1897. The company is known for being receptive to new construction techniques and as an innovator in concrete construction processes.
Using a placing boom with a long reach means the boom can remain in the same location on a high-rise job, without crane moves, or the need to add extra delivery line. In addition, Putzmeister placing booms do not require a counterweight.
On the Lancaster project, the back end of a Putzmeister 32-Meter concrete boom pump is being used as a trailer pump to push the concrete supplied by Prairie Group of Bridgeview, Ill. From ground level up to the 15th floor, the pump will accommodate both a 10,000-psi mix, required for the center of the building, and a 7,000-psi mix for the exterior and perimeter columns. A 5,000-psi mix will be used from the 15th floor to the top.
Although the 37-year-old Hoyle has worked on his share of high-rise jobs, this is the largest he has supervised. “Because of the effective setup, we’re getting about 115 yards an hour, which is 40 yards more than expected,” he said. “Of course, the faster you place the concrete, the faster you can get to the next step.”
Having started placing concrete on the lowest levels in April, the aggressive three-day construction cycle for each floor begins with the boom placing concrete for the deck for three hours on the morning of the first day. A special accelerator in the concrete allows the 13,700-square-foot area to harden in about three hours.
As the concrete cures, the crew cleans up, re-primes pumps and then starts pouring vertical interior columns and exterior columns by afternoon. A total of 430 yards are placed per level. In addition, 60 percent of the floor frame for the next level is assembled the same day. For the most part, carpenters, laborers, cement finishers and ironworkers must complete their assigned tasks within the following two days.
“The two-day-work, one-day-pour process is ready to repeat itself once a floor is finished and the placing boom and pedestal are raised,” Hoyle said. “To get to the next level, we basically disconnect the riser line, jack up the core system with the boom, pedestal and base attached, reconnect the riser line and we’re ready to pump again. It’s that simple. Since we don’t have to break from a tower, we’re saving about three guys doing four to five hours of extra work.”
McHugh Construction buys most of its construction equipment for added control in scheduling jobs. “All the placing equipment is working exceptionally well, especially the clamp-down piece,” said Pete Spear, McHugh’s equipment superintendent. “It saves a tremendous amount of labor because it’s really fast. We discovered a few helpful tricks along the way so now there’s no fooling around when it’s time to elevate the system to the next floor.”
“The clamp-down base is small, lightweight and has a flexible design so we plan to use it over again in other high-rise projects.”
Although the Lancaster project involves use of the clamp-down base at zero elevation without a tower, it also can be paired with a tower. McHugh has the flexibility of attaching it to an 80-foot freestanding tower for climbing, or a 20-foot tower within the form-frame system to accommodate future needs.
Construction of the Lancaster building began in the summer of 2003 when unit sales reached 65 percent of the planned 207 condominium units. Destined for a fall 2004 completion, the project will consume more than 18,500 yards of concrete, including an adjoining post-tensioned, four-story parking garage and multi-strand connecting bridge to the residential tower.
Construction within the Lakeshore East development is designed to bring a more orderly layout to the neighborhood. The development will encompass 9.7 million square feet and include 14 high-rise condominium towers along with two office superstructures surrounded by a six-acre park. Plans are to complete the development by 2010.
General Contractor: James McHugh Construction, Chicago
Concrete Supplier: The Prairie Group, Bridgeview, Ill.
Equipment: Putzmeister MXR 34/38 separate placing boom with Putzmeister clamp-down mounting base and Putzmeister 32-Meter concrete boom pump