At the heart of Los Angeles' Century City/Beverly Hills region, the 42-story, 147-unit luxury condominium tower known as “The Century” is designed to be an epicenter of upscale living on the Avenue of the Stars. The design includes 256 fluted concrete finished columns created with customized fiber-reinforced polymer (FRP) column forms produced by Molded Fiber Glass Construction Products (MFG-CP), Independence, Kan.
The 884,468 gross-square-foot Century Project began construction in June 2007 and is slated for completion in December 2008. The tower is supported by an interior moment frame system with a 7109-cubic-yard concrete mat foundation. Its exterior skin combines sculptured precast concrete and stone cladding. The 13-foot fluted columns will accent the floor-to-ceiling window balconies on the upper 26 of buildings' 42 floors.
Flute forming challenge
Architectural firm of record HKS Inc., Dallas, enlisted the project's concrete contractor Webcor Concrete, San Mateo, Calif., to secure a source for the column forms. Webcor contracted MFG-CP—who specializes in a complete range of custom and standard fiberglass-reinforced thermoset composite column forms—to custom build 15 FRP fluted round column forms, in addition to standard round column forms for use throughout the tower.
The goal was to create a unique fluted design, providing flexible stability for the 13-foot scale during the concrete pour and to deliver a smooth finish. To optimize production, delivery, assembly, and pour/peal time onsite, MFG-CP settled on a four-piece form design.
According to MFG-CP engineering manager Eric Brace, “We used the four-piece design versus the two-piece so it could be stripped in pieces during production to ensure a smoother finish and capture the meticulous luxury of the design.”
MFG-CP produced the fluted forms in quarter sections using a chopped strand mat sandwich construction of 24-ounce woven roving. The production used a spray up/open mold process with mold-release pretreatment that involved simultaneously depositing the chopped strand mat laid in place on the cavity mold with the catalyst resin poured over for an even flow of material.
FRP flute form results
Although created in quarter sections, the column forms were delivered as 15 full forms with four seams and 9/16-inch lip holes to accommodate ½-inch coil bolts during assembly. The forms also are corrosion resistant, making them reusable.
Upon assembly of the column form, standard rebar, and base, approximately 3 cubic yards of self-consolidating concrete were required for each pour in a standard monolithic pour sequence. Webcor's senior superintendent Ryan Isbell, “Construction to date is meeting the aggressive six-day cycle—one-floor every six days—as the fluted forms are an easy pour, taking approximately two to four minutes per column.”
According to HKS architect Patrick Treadway, “The tower's fluted concrete columns were more cost efficient than the originally conceived precast or stone options and provided a practical alternative for time, design, and efficiency.”