16 April 2003
Collaboration between designer, contractor and engineer - a different way of working
Cristobal Correa, associate in Buro Happold’s New York office, uses his experience of Buro Happold’s work with glass designer James Carpenter Design Associates and contractor Tripyramid to illustrate the power of a holistic approach as a strategy better able to deal with new technologies, achieve tight deadlines or simply produce a better result.
When a client purchases a singular work of art from renowned glass designer James Carpenter Design Associates (JCDA), the traditional route of design-engineer-construct doesn’t work. The demands on the structure, the originality of the materials and technologies and the tight link between form and function prevent the project roles from being performed in the conventional way. Instead, a holistic approach allows the team members to adapt their designs to the constraints that exist in all three fields.
This holistic approach was used in the procurement of a sculptural piece installed in the main lobby of the Cannon Performing Arts Center in Downtown Memphis in December 2002. Approximately 55 feet long, six feet wide and 10 feet high, the sculpture is made up of a series of repetitive elements (see figure 4). These self-stabilizing repetitive elements, measuring three feet by four feet, are made up of glass compression elements and stainless steel cables, with a fabric cladding.
The elements were brought together to make a curved beam configuration supported at its approximate quarter points to points in the building lobby ceiling. The lateral stability of the sculpture is provided by eight attachment points (four on each side). These are connected to two columns located on either side of the atrium at two different heights. The location and typical detailing for these attachment points had already been provided in order for the building base build to be completed without the sculpture being completely designed
JCDA’s original designs were based on their own concepts and extensive knowledge of engineering behavior and construction. Study models were constructed in order to appreciate the design qualities and to communicate with the client and the rest of the design team. Figure 1 shows the initial idea of a sculpture for Cannon PAC, based on a modular unit made up of a triangular metal frame, glass strut, tension cables and fabric in tension.
The designs were then refined in a series of team meetings between all consultants. These meetings allowed certain elements to be modified, added or eliminated, structural elements to be roughly sized, and critical areas to be identified. The overall structural behavior and level of analysis was discussed and the technologies needed for the creation of the structural elements and the installation of the sculpture were evaluated.
For Cannon PAC, these meetings established preliminary sizes for the element as well as a rough idea of the loads that would be placed on the supporting structure. Additional elements were added to increase the rigidity of the piece and reduce the complexity of the required analysis. The decision was made to keep the fabric as cladding only and to replace its tension function with rods which would be easier to detail and would provide a much higher degree of geometrical precision.
After these discussions JCDA provided preliminary drawings which were turned into structural models. These models provided a more reliable sizing of the elements and a better understanding of the required level of analysis. Another design meeting was called to discuss the final analysis, the areas where critical analysis was needed and to review construction strategies. For Cannon PAC the construction of the nodes was examined as tolerances for assembly had to be built in while maintaining an element of geometry that was simple and repetitive.
Final structural analysis was done based on the structural model shown in Figure 2. These calculations were documented in report form for distribution to the team. The contractor then took this information and began the task of detailing the components for the generated loads, coordinating with JCDA in order to evaluate fabrication processes and desired design aesthetics. The contractor developed detailed models that allowed the evaluation of stresses in the actual pieces in order to check the design and provide exact dimensions and geometries for the components. The contractor generated shop drawings shown in figure 3, which went back to JCDA and to engineer Buro Happold in order to provide a level of review and ensure that the design intent has been followed.
Installation strategies were then developed and reviewed with the entire design team. For Cannon PAC installation was done from a staging platform with assembly beginning near the pick points and working outward. Once the installation strategy had been agreed, installation proceeded with any site queries being referred to the engineer or to JCDA. Figure 5 shows the completed sculpture.
The Cannon Performing Arts Center is a successful example of the value of a collaborative approach, rather than the traditional way of working. All three trades working together during the entire life of the project from beginning to conclusion gives each member increased ownership of the project. The Cannon PAC team found this approach so effective that it has repeated the process on two more collaborations: a suspended sculpture in the atrium of Macalester College, Minnesota (figure 6) and a glass prismatic skylight suspended over the central staircase of a residence in Sarasota, Florida (figure 7).
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Buro Happold is a multi-disciplinary international practice of consulting engineers established in 1976 offering civil and structural engineering, mechanical and electrical engineering, quantity surveying, building services and environmental engineering, health and safety management, infrastructure and traffic engineering, ground engineering, façade engineering, fire engineering, computational fluid dynamics analysis, disability design consultancy, project management, urban design and a range of specialist CAD services.
