With more than 2.8 million residents and a constant influx of people, the need for housing in Chicago is never ending. To meet this growing need, new residential condominiums are being built at 2520 N. Lakeview on the northside of Chicago.
The 800,000-square-foot condo development is built on a standard flat slab. The square-column, concrete-framed building has two large cores, which are uniquely shaped and have floor-to-ceiling heights that vary throughout.
Choosing the formwork
To meet the demands of this particular building design, it is necessary to cycle the vertical formwork at the same speed as the horizontal formwork. Chicago-based Walsh Construction Co. wanted to pour the slab and floors monolithically and needed a forming system that could easily meet those challenges. Additionally, the formwork system had to be capable of carrying a concrete placing boom, provide support for heavy loads (such as rebar), and be able to keep the crew on a one-day cycle. For these reasons, Walsh chose Doka’s Super Climber self-climbing form system with working platform for high-rise cores. This system, Little Ferry, N.J.-based Doka’s newest member of its multiple climbing formwork systems, meets the tough requirements of extreme dynamic loadability with swift, smooth climbing. The manufacturer’s X-climb automatic climbing formwork is being used on the north core.
“The Super Climber was chosen because of its simple anchoring application and the ease of a component bracket base setup,” says Steve Likens, superintendent for Walsh Construction. “The high load-bearing, rigid super structure is engineered for a mounted concrete placing boom, and the impressive hydraulic climbing cylinders and pump provide us with a safe, fast, and efficient lift from floor to floor.”
Using two self-climbing core systems allows Walsh to cycle the cores as fast as the slabs. The formwork systems allowed for prefabrication of panels and platforms, which help limit the amount of onsite work. By using this formwork system, Walsh could meet its schedule and minimize the amount of man-hours on the project.
Meeting project demands
The 39-story structure needs approximately 2300 square feet of formwork. There are varying floor-to-floor heights with two double jumps. A total of five hydraulic cylinders are used to climb a fully decked Level +1 and Level 0. Custom beams support a concrete placing boom, and Framax stripping corners are incorporated into the Top 50 wall formwork for easy stripping relief. Formwork used included: one Super Climber system with Top 50, one X-Climb with Top 50, Frami lightweight formwork for columns, eight MF240 platforms, 54,000 square feet of Dokaflex handset system and 72,000 square feet of reshoring materials.
The self climbing core system also offers faster cycle times, allowing inside and outside forms to be hung from the gantry and the contractor to roll forms while erecting and stripping. All of the formwork for an entire story is raised independently of the crane. Minimum clearance is required for installation and minimum stripping needed for climbing. A placing boom with a working platform can be attached to the gantry to provide access. Forms, platforms, and the placing boom are all cycled at the same time with minimal climbing time and climbing can be completed in one smooth movement. Service loads remain on the platforms while they are raised.
“The system is great to work with and climbs in less than 20 minutes, meeting our demands,” says Matt Code, a carpenter foreman with Walsh Construction.
“The Super Climber system was used to climb the mounted placing boom,” says Nicholas Zaraza, project leader/engineer, Doka USA Ltd. “The rigidity of the superstructure in cooperation with the hydraulic cylinders provides the contractor with an elite formwork system capable of carrying high loads and providing safety.”
All operations can be carried out safely and quickly on the formwork’s large, fully enclosed workspace, because the climbing formwork system is anchored to the concrete at all times. The whole “site” is repositioned hydraulically with just one lift. This self-climbing core system is a safe and efficient way to construct high-rise cores, with room for all site equipment, and enclosed on all sides for safe, weather-shielded labor at any height. The live loads on the platform mean less storage space is needed on the ground. After pouring, the formwork for an entire next story is raised by powerful hydraulic cylinders from one casting section to the next.
Walsh has been extremely pleased with the formwork system. The project was delivered at a competitive price because the formwork lowered the man-hour cost. Also, the project will be completed on schedule thanks to the ability to cycle the formwork from floor to floor. Work on 2520 N. Lakeview began in August 2010 and is scheduled for completion by fall 2011.