Owner: Emerson College, Los Angeles
Owner’s Rep: Silverman Associates, Newton, Mass.
Architect: Morphosis, Culver City, Calif.
*Structural Engineer: John A. Martin & Associates, Inc., Los Angeles
General Contractor: Hathaway Dinwiddie Construction Co., Los Angeles
Fabricator: Schroeder Iron Corp., Fontana, Calif. (AISC member / AISC certified fabricator)
Detailer: Schroeder Iron Corp., Fontana, Calif. (AISC member / AISC certified fabricator)
Erector: Bragg Crane & Rigging, Co., Long Beach, Calif. (AISC member / AISC certified erector)
Consultant: KSA Design Studio, Marina Del Rey, Calif.
Consultant: Waveguide Consulting Inc., Los Angeles
*Firm that entered the project in the IDEAS2 contest
Emerson College Los Angeles is the West Coast home of Boston-based Emerson College. Located in Hollywood, this $85 million building is a small scale university campus containing below-grade parking, classrooms, performance space, offices, and student housing. An iconic structure located on Sunset Boulevard, the facility supports the revitalization of a struggling neighborhood while serving as a conduit for Emerson students to intern within the nearby entertainment industry during a work/study semester in Los Angeles. The complicated forms and interconnecting spaces required creative structural problem solving to maintain efficiency of material and constructability while upholding the architect’s vision.
The nearly square footprint of the building is based three stories below-grade and rises in that shape up to the 3rd level. Above that level, the square shape of the building is broken into two separate pieces: the Eastern tower -- a slender rectangular floor plate housing residential units, and the Western tower – a combination of academic space and administrative offices in an irregularly shaped slab adjoined with residential units. The two towers continue to climb, with the Western tower’s shape continually changing, until the 6th level when the West tower reduces to a near-mirror image of the East tower. The towers terminate at the 11th level roof where they are connected by a helistop spanning over the academic structure below.
Mild reinforced concrete slabs are the gravity framing system for the parking, administrative, and office spaces. The residential towers are framed using post-tensioned concrete slabs, and the academic form is supported by steel beams, steel columns, and concrete over metal deck. Interconnectivity of the multiple systems was addressed by careful detailing and consideration of the construction sequence.
The amorphous shape of the academic building presented further structural challenges because of the two intertwining forms and varying floor-to-floor heights between residential and academic program areas. The academic building features a hanging boardroom, simultaneously reinforcing the architect’s desired massing and providing a column-free entry pavilion at the 2nd level. To support the academic forms, multiple cantilever elements were outfitted with steel cantilever trusses, one supported by the concrete elevator core walls and the other supported off of steel columns terminating at concrete transfer girders. Discontinuous special concentric braced frames and discontinuous steel moment frames were used to transfer lateral forces from the roof of the academic building down to the supporting concrete transfer diaphragm at Level 3.
The primary lateral resisting system below the third level is special reinforced concrete shearwalls. The residential towers are laterally supported in the short direction by concrete shearwalls, while the long direction is supported by special concrete moment frames which terminate at the bases of the towers. The use of moment frames that were nearly the entire length of the floor kept the forces in the beams low and allowed a shallow structure to minimize floor height. Below the 3rd level of the Western tower the supporting columns slope, creating a horizontal gravity thrust that needed to be accounted for in the lateral system. The use of multiple (and sometimes discontinuous) lateral systems required close coordination with the building department to provide a clear picture of load paths and strength demands, facilitating understanding and eventually acceptance of the design.
The helistop that connects the East and West towers of Emerson College is supported by 11 120-ft-long, 5-ft-deep castellated beams. The castellated beams start with a standard wide-flange beam which is pattern cut in half longitudinally. The two halves are then separated, staggered, and welded together to form a castellated beam. The castellated beam weighs the same as the original beam, but is 30 percent to 50 percent stronger and 50 percent deeper, thus adding structural load capacity and stiffness without adding weight.
The connection of the two towers, at both the roof and bridges at Levels 5 and 6, created structural challenges accommodating the differential deflection of the separated elements. To minimize the movement of the towers, which tended toward deflection amplified by torsional effects, the helistop was ultimately used as a diaphragm to control the torsional deflection of the residential towers. This allowed separation joints between elements to be minimized, as well as provided reduced deflection criteria for the sensitive curtainwalls and scrims cladding the towers’ exteriors.
A singular and complicated design like Emerson College can only be created and explained using 3D models. Multiple building information modeling (BIM) platforms were used by the design teams but were combined to coordinate the structure with the architecture.
In developing the structural model for the academic form, multiple iterations of geometry refinement were coordinated with the architect’s model. The thickness of the exterior assembly was determined by the factory-assembled panel system, including tolerance and connection details, and the structural shape was set using a 3D shell created by offsetting the architect’s exterior shape. Through close collaboration, both the aesthetic and functional intentions of the architecture were used to aid in shaping the appropriate structural systems and geometry.
Numerous subcontractor models, in addition to the structural, architectural, and mechanical models, were combined for multi-discipline BIM coordination and conflict identification, solving problems before they appeared in the field. During construction, 3D models (along with traditional 2D drawings) were submitted by the structural steel contractor to more clearly explain the unique geometry and details required at the academic form. The appropriate use of design and coordination programs contributed to the successful delivery of Emerson College Los Angeles on-time and on-budget.