ADC Telecommunications World Headquarters Structural Engineering
Eden Prairie, MinnesotaFor the new World Headquarters for the ADC Telecommunications Corporation, the architects at HGA sought a structural program that would identify with the technical, systems-oriented nature of the client's work by exposing the systems within the building to view.
Structural components would be left exposed as often as possible in order to illustrate the interrelationships between them as well as develop a sense of hierarchy and completion.
The structural engineers worked closely with the architects and model builders as various concepts were explored. The architects sought to create in the exposed structural framing a particular form which would clearly identify the work areas within the building. The team's solution was to create pairs of custom prefabricated truss girders at each column line. These trusses are unusual in that they extend past the columns on each side to support corridors and the exterior wall. Standard wide flange beams are employed as purlins between the trusses. In this manner, a regular and disciplined hierarchy of members was created: each particular size and shape is used for only one particular purpose, and the flow of forces is readily apparent even to the non-engineer.
The most interesting technical issues on this project related to the design and detailing of the custom prefabricated HSS trusses. There were over 700 individual trusses on the job, creating the opportunity for economies of scale. Direct welded connections were employed throughout, which yielded labor savings in the shop and eliminated unattractive gusset plates. A Warren truss geometry was selected, which required the least number of connections and opened up the truss for mechanical systems to pass through. The geometry of the trusses was such that gapped connections were possible everywhere.
The design of direct welded HSS trusses follows a somewhat different sequence of steps than trusses constructed out of wide flanges or using gusset plates at the connections. Because the capacity of the connections is dependent upon the wall thickness of the members being joined, the design of the connections becomes an integral part of member sizing. In addition, careful re-analysis of each truss must be performed to incorporate secondary moments that result from the connection designs.
The truss to column connection was perhaps the most unusual condition on the project. The connection would need to cantilever out to pick up the truss as near to the truss centerline as possible, provide for installation tolerances, and also permit in plane rotation of the trusses at the support. It was essential that the connection be field bolted, both for the erection schedule and project budget. The fabricator and engineer worked closely together to solve this complex problem.
The ADC World Headquarters project presented an exciting opportunity to the structural engineers to see their work integrated as a vital part of the architecture and experience of the building. It became necessary to think in new ways in order to achieve what was conceived by the architects, and to be flexible and willing to explore unusual ideas. The collaborative, multidisciplinary environment of HGA was the perfect catalyst for this innovative project.