No Small Contribution

The Vagelos Education Center at Columbia University Medical Center

New York, New York

Creating An Innovative Learning Environment

The Vagelos Education Center at Columbia University Medical Center is a 100,000 square-foot, 15-story, state-of-the-art medical education facility, whose multifaceted goals include the linking of students and teachers, of interdisciplinary study and interactive learning, and of function and experience, all while providing an identity and focal point for Columbia University’s Washington Heights campus. CUMGEB aspires to be an iconic facility for the university and neighborhood, helping to attract the world’s top medical students.

The design team included Diller Scofidio + Renfro (DS+R) in collaboration with executive architect Gensler. Leslie E. Robertson Associates (LERA) provided structural engineering services. F.J. Sciame Construction served as the project’s construction manager.

The project’s main feature is a southern facing “Study Cascade” that contains interconnected study and social spaces to encourage collaboration between students. The study cascade is envisioned as a vertical campus of stacked “neighborhoods”, which are two to three-story, near atrium-like clusters of diversified social spaces. The southern campus-facing façade is a highly articulated all-glass system that is crucial to the building’s expression. The northern half of the building is organized for classrooms and administrative space, in addition to a mid-tower mechanical space to accommodate the needs of the building’s Anatomy Labs.

Responding To Building Design Challenges

The Vagelos Center’s main structural design challenge was to find vertical load paths through the Study Cascade while respecting the varied spatial planning of the stacked neighborhoods. To minimize the structure’s impact on these spaces, the cascade floors are supported by a pair of inclined composite concrete columns that are architecturally exposed and cast with high strength (10 ksi), self-consolidating concrete. These two exposed columns slope from the foundation level up to the 8th floor in order to direct loads around a column-free auditorium at the base of the Cascade. The thrusts that result from the changes in direction of the sloping columns are resisted by in-floor trusses constructed with post-tensioning and high-strength rebar.

An additional structural challenge was to provide long, open floor spans with minimal structural depth that could simultaneously accommodate the tight deflection performance requirements of the all-glass façade. The cascade structure has no perimeter columns, which results in a unique sequence of cantilevered concrete flat slabs. To meet the slab performance requirements, the cantilevered slabs are reinforced with a bonded post-tensioning system. Void formers, manufactured by Cobiax USA, are placed between bands of post-tensioning to create long-span, beam-like framing with flat formwork and to reduce the structure’s self-weight. The cantilevered slabs utilize high-strength concrete (8 ksi) and taper in thicknesses from 24 inches at supports to 8 inches at the cantilever tips.

The curtain wall of the cascade is arranged in multi-story planes that do not align in plan between neighborhoods and are not parallel with the slab’s edges, creating detailing challenges for both the structure and façade. Through a design-assist phase, expected deflections from slab curvature were coordinated at each glass mullion with the curtain wall contractor, Gartner, and together the project team decided on an acceptable long-term deflection limit of 1¼ inches for cantilevers up to 26 feet. The bonded post-tensioned slabs were tuned to meet these performance requirements and were detailed to accommodate a range of façade attachment methods.

Although the project is relatively small in area, The Vagelos Education Center is a complex building with broad aspirations. The design and construction challenges of Center are similar to those often found in much taller buildings and longer-span structures. The goals of the project were achieved through the successful use of proven construction technologies, extensive analysis and coordination, and strong integration of architecture and structure.

The Role of Cobiax Voided Concrete System

To accomplish the design’s long cantilevers, the floors are formed of bonded post-tensioned concrete slabs. A Cobiax slab void former system is used to reduce the self-weight of the slabs in addition to other benefits.

The biaxial voided slab technology allows large spans, efficiently formed as flat plates without beams, while using significantly less concrete than if solid.

Plastic voids in the shape of spheres or flattened spheres are contained in steel cages and put into the concrete structure to create longer spans and reduce vertical loads. Multiple void sizes can be provided for a wide range of flat slab depths depending on span requirements.

The CobiaxUSA system provides a number of other benefits:

• The ability to create large spans and cantilevers without beams significantly improves design flexibility for the architect

• Less depth of structure also means lower floor to floor heights or more head rooms

• The biaxial load transfer reduces deflections

• Reduced vertical loads reduce column and foundation sizes and the need for earthquake reinforcement

• A flat plate design minimizes costly and time-consuming vertical formwork

• An environmentally sound solution: the system incorporates recycled materials and reduces the need for direct building materials, as well as building volume

All slabs above the ground floor contain Cobiax void formers. Specific challenges were to assure proper concrete coverage and coordination with slab embedded items including MEP sleeves and box-outs. Specific attention was paid to the Cobiax void hold-down system to prevent buoyancy.

Void formers were originally conceived only for the 2 to 3rd-floor auditorium ramp which consists of a 25” thick slab. During design development, the void forming scope was expanded to lessen structure self-weight and to provide some cost savings. Cobiax specifically was utilized for its flexibility in accommodating different geometries and slab thicknesses with a standard unit.

Project Recognition:

Helped project attain LEED Gold Certification

Roger H. Corbetta Award, Concrete Industry Board (CIB)