Precast Concrete Panels Used to Support Structural Concrete
The new Academy Museum of Motion Pictures in Los Angeles was created to celebrate the art and science of movies—past, present, and future. And what better way to do that than to create a structure that looks like it could have rolled off the set of a Star Wars movie?
The project involved the exterior restoration and interior gut renovation of a 230,000-ft² historic landmark structure, with the addition of a 60,000-ft² spherical glass and concrete structure to house the 1000-seat David Geffen theater. The 150-ft diameter precast concrete sphere appears to float above ground, offering a whimsical counterbalance to the more sedate renovated historic structure.
The sphere was originally conceived as a cast-in-place concrete shell, but as the design evolved, it became clear that cast-in-place was not the right solution. “Spherical formwork would have been prohibitively expensive for carpenters to fabricate and assemble on-site,” says Daniel Hammerman, architect for Renzo Piano Building Workshop. “Precast concrete allowed for better and more cost-effective finish quality and tighter tolerances and geometry control to ensure a perfect sphere.”
Because the sphere features a consistent radius, the project required only 30 base molds, which could be reused many times with only minor adjustments of edge forms and blockouts. The use of precast concrete also allowed the large, column-free space, providing unobstructed sightlines for the theater in the round, as well as providing the physical mass necessary for acoustic isolation of the high-performance theater.
Initially, designers were concerned that precast concrete would not be able to deliver the desired variation in the finish. “Precast concrete tends to prize a consistent, uniform look of factory-made cladding panels,” says Hammerman. However, the precast concrete producer generated multiple samples and mock-ups to ultimately define the best technique to achieve the intended finish appearance. The final design used a standard gray cement and a single aggregate to produce all of the panels.
Rather than using a typical sandblasted finish, which erases all the flaws but also the character, they opted for an “as-cast” finish to impart a luminous surface quality. “The gentle sheen on the soffit panels above the plaza brings fantastic daylight and reflections underneath the mass of the sphere, helping create a wonderfully welcoming public plaza,” Hammerman says.