The Employers Mutual Casualty Company (EMC) 8th Street four-story office building in downtown Des Moines includes below-ground parking, conference rooms, and a wellness center. A skywalk concourse will connect the new building with an existing EMC building. Concrete contractor, Neumann BrothersEFCO, which supplied the formwork.
Starting off the project, Neumann used plate girder forms for all of the large footings and the tower crane slab. Once this was complete, Neumann turned to lighter-weight forming system to handle the foundation walls.
Twelve-foot-tall round column forms with diameters of 24 inches and 30 inches were used in the basement. The two-piece column form with high-strength connection bolts only on 2-foot centers and a split washer provided a labor-saving benefit for setting and stripping the entire form with one pick of the crane. Tight precision face sheet joints minimized offsets and grout leakage while delivering a quality concrete finish.
Neumann used EFCO's guided rail system (GRS) and light wall formwork to build the elevator shaft for this new building. The GRS is designed for safety and efficiency, which starts during assembly and continues through installation and all the way up the structure. The GRS gangs are assembled on the ground installing work decks and preparing the form rollback systems. The built-in rails of each gang remain attached to shoes installed on previous pours, allowing a crane to lift the setup while continuously attached to the wall. Gangs can be lifted and set for the next pour in minutes.
The GRS was installed on the core after the first 13-foot-tall pour was complete. The integrated roll-back assembly on the GRS frame allows the formwork to move back 30 inches providing easy access to formwork and clearance for rebar installation. The CAM Rollers provide smooth operation, and the formwork can be pushed back and forth by operators alone. The system also includes a ratchet for mechanically retracting the roll-back in windy conditions or large formwork gangs. Using the roll-back feature on the GRS, the iron workers were able to complete their work where they positioned rebar, block outs, embeds, ties, and anchors for the forms. Developing this plan in advance, the Neumann and EFCO engineering teams made this project a success.
The contractor used a shoring system to form the 19,000-square-foot first floor deck. The waffle slab design for the first floor has variable slab depths of 2 feet, 2 feet 6 inches, and 3 feet along with several elevation changes. Neumann used modular deck shoring towers with long and short jacks to account for the change in elevation and sloping floor support. The shore towers supported contractor-supplied steel tubs to form the pan deck design.
The project is expected to be completed in early 2017.