Chicago high-rise with self-climbing formwork

Concrete Construction, July, 2003

Number 55 East Erie, the latest high-rise residential development in downtown Chicago, is being built with the aid of Doka automatic self-climbing systems with wall formwork elements suspended from the platform. This makes it possible to concrete the entire core, slabs, and facade walls in a single pour, saving valuable time and manpower.

Prime contractor Walsh Construction is currently progressing at a rate of one floor every 4 days on the new, main 56-story, luxury residential tower. The building has a footprint of 25,000 square feet. A 12-story parking garage rises from street level with the main tower beginning at level 14.

Lower level construction

Walsh Construction used two self-climbing systems to form the garage's two cores and then moved on to the main tower's two central cores. Between the garage and the main tower, two transfer levels (12 and 13) have been constructed with extra-heavy concrete beams to distribute the weight of the tower. Because the parking garage is on the floors below, there are wide-open areas with no columns. The transfer beams on the 13th floor are 16 feet high and deep, and they were poured in two stages of 8 feet each. The first pour was designed to support the concrete weight of the second lift, and all shoring and re-shoring were released from any loads before pouring the second lift. This method, according to Martin Horlesberger, Conesco Doka's Midwest regional manager, let Walsh rent less shoring than would be expected, and reshoring wasn't required all the way down to ground level.

Climbing systems

The contractor is using two self-climbing systems on the main tower. One system of 10 Doka SKE100 climbers supports a concrete placing boom, while the other system has six climbers. The self-climbing systems are lifted by automatic climbers together with wall formwork suspended from the platform, allowing the shaft to be lifted in a single operation.

The climbing system has also enabled the contractor to concrete not only the central cores and slabs, but also the facade walls, in one pour. This entire method has cut down on material costs by eliminating the need for couplers connecting slab reinforcement to the core and facade.

The exterior columns are poured from the slab up because there are 10 balconies to be poured together with the slabs. The exterior of the tower is crane-lifted because it changes at two transitions (the tower narrows slightly at level 34 and has no balconies from level 48 on up).

Walsh used two floors of shoring and three floors of re-shoring for each slab. Each slab is 8 inches thick, and Walsh estimates that 500 cubic yards of concrete is poured per floor, with an extra 40 cubic yards per floor for the two cores. All formwork for the main tower slabs was set and stripped by hand.

The typical cycle on the tower consists of stripping the formwork, lifting it to next level, laying rebar, setting up formwork, and then pouring concrete. The self-climbing system keeps pace with the slabs and columns, and also supplies the concrete placing boom.

As the tower progresses, the concrete strength needed for each pour slightly decreases. For the 12-story garage, Walsh used 12,000-psi concrete, decreasing to 10,000 psi by the 14th level of the main tower; by the time the building tops out, the strength will be 8000 psi.

The main tower will house luxury residential units, with six units on levels 14 to 33, five on levels 34 to 48, two on levels 49 to 55, and, on level 56, just one penthouse suite covering the entire floor space.

For more information on Conesco Doka forming systems, call 800-631-1978, www.conesco.com or circle 8.