Urbandale, Iowa, just west of Des Moines, will soon be the home of Citigroup's new 180,000-square-foot credit card processing center. Concrete Strategies provided design, engineering, and construction services for the project, one of several the firm has completed for Citigroup.
Ground was broken Aug. 1, with the last concrete panel tilted into position Sept. 7. By the 38th day, Concrete Strategies had completed the floor, formed and cast all of the wall panels, and tilted them into position. Each of the 30-foot-wide panels was 13 inches thick with a 2.5-inch concrete exterior face, a 2.5-inch polystyrene foam insulation core, and an 8-inch-thick structural concrete interior. The tallest panel was 44 feet and the heaviest, with rigging, weighed 169,000 pounds. A 300-ton crane lifted the panels into position.
Usually, panels are lifted only once as they are moved into position. But the design of the building's entrance calls for three panels to interlock in a triangular fashion. This meant lifting the panels twice; once using face-lifting techniques to move them into a vertical position, and then switching the rigging to the top of the panels to perform an “edge lift,” or “plumb set,” that allowed the panels to move straight down into position—a highly skilled crane operation for the crew.
Historically, many buildings in the Des Moines area have been constructed using precast concrete panels, however tilt-up construction was selected for this facility because of the speed, design freedom, energy efficiency, and cost competitiveness. “This system worked perfectly in terms of cost and construction. Precast companies were not able to meet the project delivery schedule and were not able cast 30-foot-wide panels,” said Jeff Elder, Concrete Strategies' general foreman.
The 13-inch-thick integrally insulated panels are held together with structural-grade, non-thermal bridging fiber composite connectors which sandwich the 2½-inch THERMOMASS Insulation System between a 2½-inch exterior concrete wythe and an 8-inch interior structural concrete wythe. The design maximizes the energy efficiencies of the walls and creates a thermal storage capacity on the inside of the concrete building shell.
To give the building a corporate look with a brick veneer, Scott Systems' Brick Snap was selected. Gaskets used to hold the brick in position when the concrete was being placed are still visible in the photos shown here. This fast-track project is expected to be completed in late November. The project owner is R&R Realty Group of West Des Moines, which is leasing the facility to Citigroup, the nation's largest financial services company.
- Owner: R&R Realty Group, Des Moines, Iowa
- Design Architect: Forum Studio, St. Louis
- Structural Engineer: Alper Audi, St. Louis
- General Contractor: Clayco, St. Louis
- Tilt-up Contractor: Concrete Strategies, St. Louis
- Ready-Mix Supplier: Concrete Supply of Iowa, Des Moines
- Concrete Testing: GSI, Des Moines