The glittering new $189million Edward P Evans Hall at the School of Management in Yale University opened in January 2014. The 242,000sq ft. structural system with exposed exterior columns was developed by Buro Happold. The new facility boasts a curved, four-storey glass façade with slim interior vertical elements and intricate connections formed using structural steel, thus achieving the demanding architectural vision of providing unobstructed views both the inside and outside. Evans Hall will double the size of the School of Management and house diverse classroom spaces arranged around a central outdoor courtyard. It includes an academic centre, study areas, a 350 seat auditorium and parking for 150 vehicles.
An opening for Steel
“ Foster + Partners envisaged a four storey, curved glass façade to serve as a prominent feature in the courtyard, with the façade supported only at the top and bottom. The design team decided to hang the façades weight entirely from the roof, with the bottom support used only for bracing
The building is comprised of five stories above grade and two stories below grade. Buro Happold used a steel construction for the above grade structure and reinforced concrete flat slab construction with drop panels spanning to cast-in-place columns for the below grade floors. The engineering team used 1,900 tons of steel for the above-grade portion because it was considered the best material with which to achieve an architectural design allowing for large, column free areas and clear unobstructed facades. During the early project phases, both cast-in-place and pre-cast concrete were explored as options, however only steel could deliver such an open design and still provide the necessary structural support.
Foster + Partners envisaged a four storey, curved glass façade to serve as a prominent feature in the courtyard, with the façade supported only at the top and bottom. This made an atrium within the building as it bypasses intermediate floors. To realise this long term vertical span without needing large structural members that would interrupt the view, the design team decided to hang the facades weight entirely from the roof, with the bottom support used only for bracing. Buro Happold designed custom steel sleeve connections to integrate the facades vertical element with the second floors structural steel. This allowed seamless integration and vertical movement between the second floor and the façade, even though separate contractors were employed.
Halfway up the façade a mezzanine extends but does not connect. This created a cantilever situation ranging from 10ft to 17ft that had to fit within the thin floor profile. To achieve this, W27 cantilever beams were designed for strength and 2 inch diameter deflection control hanger rods were added at the end of the cantilevers. As the rods were designed for deflection control only, they did not require fire-proofing which lessoned the structures impact on the architectural design. The auditorium, located beneath a proposed space for entertainment had strict acoustical criteria in terms of vibration and noise transfer for the structure supporting the space. Buro Happold designed deep plate girders for the 50ft span and made provision in the design of the plate girders to accommodate penetrations for the building systems, as the steel members took up all of the available ceiling space. The criteria for limiting noise transfer into the auditorium from the space above was met via a 7inch thick normal weight concrete-on-steel deck slab.
The architecturally exposed structural steel (AESS), while part of the desired aesthetic, presented several challenges. These columns would be exposed to view from both inside and outside of the building and the architects wanted them to feature a thin elegant profile. They also had to be designed to incorporate thermal effects, since the roof hung façade was supported on the exterior columns, their design had to be coordinated with the façade contractor. The exterior HSS columns ranged up to 64ft tall and are unbraced, yet had to support a significant portion of the floor, this created undesirable fire issues. To resolve this, Buro Happold performed detailed fire engineering studies proving that these HSS18X1/2 could do a better job withstanding fire than the local building codes had anticipated.
Right from the beginning of the project it was clear that the buildings success depended on the team working together to solve its geometrical complexities. The design team leveraged Revit modelling at the start of construction documents to allow real time 3D coordination of all trades. While this proved helpful, it became apparent that more advanced BIM was required on several fronts.
The architects vision left very little room in the ceiling void for both the MEP and the structural systems. Further complicating matters, a zoning decision had reduced the buildings plan area while not allowing an increase in height. An additional floor had to be added, reducing available space in the ceiling cavity. The only way to ensure successful construction was to deliver design team coordinated models to the contractor; these models would need to be “clash-free” prior to handover. Structurally, this involved detailed modelling of complex steel geometries and connections as well as MEP system penetrations throughout the building. According to Erleen Hatfield, Regional Discipline Leader, Structural Engineering North America at Buro Happold “the University’s clash free requirement really challenged our design team to create a coordinated design and then demonstrate this. Using sophisticated technologies such as BIM, our engineers successfully managed this complex project and completed it to everyone’s satisfaction”.
Nigel Dancey of Foster + Partners tells us a little about the new hall at Yale School of Management
IGS: The atrium plays a significant role in bringing and bouncing light around the interior of the building. How early was it decided to include an atrium and can you tell us how the complex geometry of the building is designed to distribute the natural daylight?
The design of the atrium evolved over time. We tested the design for daylight performance throughout the year, and we were able to achieve a high level of transparency by shading the glass where necessary and by using high performance, low-iron glazing in the public spaces. The atrium’s complex geometry and sun-shading balance the need for daylight, views and transparency. We were delighted that Yale engaged the artist Adrian Schiess to work with us on this part of the building. He has created a wonderful mural that uses natural light to bring a dynamic quality to the space – the installation appears to change colour as the viewer moves around it
IGS: On a high performance project of this type, how much more difficult would it have been without BIM? And would the project have kept to the timescale and within budget if such a system was not used?
We used BIM to coordinate design and construction – employing its technical capabilities was particularly helpful in integrating the radiant flooring and displacement ventilation systems with the structure within very challenging floor-to-floor dimensions.
IGS: They say you learn something new every day, what valuable lesson did you learn from working on this project?
Sometimes the hardest thing to achieve in architecture is a sense of simplicity. I think our building for Yale is a good demonstration – using very simple design elements, such as scale and transparency, it has been possible to create an impressive, dynamic and highly functional space.
IGS: Was the project designed from the outset with any particular LEED (or other) certification in mind?
The university was keen to target LEED ‘gold’ from the outset, but their primary concern was an overall reduction in carbon footprint. Every decision as the design evolved was taken with carbon reduction and a holistic approach to environmental issues in mind – this was a natural way of ensuring a sustainable approach that would fit the unique needs of the project, rather than having a prescriptive environmental agenda drive the design.
IGS: IGS is a glass magazine so I have to put this question to you, why did you use structural steel as opposed to structural glass? Imagine if those concrete columns were made of 100% glass, how sexy would that have been? We have the technology you know…
The courtyard curtain wall is in tremendous tension – it is not attached to the ground, but is hanging in the air. It was designed and constructed by Gartner in Germany and Permasteelisa North America. Alternative solutions would have required cables anchored in the ground, which we did not want. The horizontals accentuate the curve of the façade and – visually and structurally – they are a necessary part of the design.