Fifth Parking Garage

11-STORY DOUBLE-HELIX MULTI-USE PARKING GARAGE

Des Moines, Iowa

Rising up to replace an outdated precast parking garage in Des Moines, Iowa, the Fifth Parking Garage houses street-level retail space and 11 levels of public parking. Two additional levels are reserved for amenity decks for a planned 42-story tower to be constructed next door in the rapidly growing city.

Ceco provided horizontal and column forming services for the beam-and-slab post-tensioned concrete garage, which contains 282,000 square feet of elevated structure utilizing 27 x 60-foot elevated bays. Because the garage has a unique double-helix design that expedites parking, Ceco provided schedule guidance during the budgeting phase to help keep the complex build on track.

The design is a two-bay-wide double helix with crossovers at every other floor and two speed ramps located at the ends of each bay. This means very few areas of the 120 x 223-foot garage are flat, which presented work continuity and elevation grading challenges for the Ceco team during construction.

Careful coordination was required to ensure all trades and concrete operations were in sync so that team members were ready to build upon the concrete that seemed to be poured below them as the double helix unfolded. Consequently, the team broke each level into three pours (north helix, south helix, center), with pours taking place in round-robin fashion as one helix level chased the other. When 80-percent of the first pour was complete on the north helix side of the floor, the second pour began on the south side. When 50-percent of the second pour was complete, the third pour began at the center.

Another design feature was floor-to-ceiling heights of up to 23 feet at the first level to accommodate retail space. The Ceco team used tall Titan shoring to support the loads on the lower level. For the parking levels, the team used Ceco’s 60-foot steel beamforms and 25-foot-long deck panels to mechanize and expedite the deck formwork operations. See the Ceco Structural BIM video for details.

Project Documents

Project Sheet