With a height of 297 m, the new headquarters of digital television provider Comcast is the new record-holder in Philadelphia, the largest city in the US state of Pennsylvania. The 51st to 54th floors of this 57-storey building are reserved for the management. From here, senior managers can enjoy a breathtaking view over the city and also a separate 20 m high all-glass self-supporting staircase linking the management floors.
All-glass stairs are no novelty for seele. However, extending over four storeys and nearly 300 m above the ground was a new challenge! Deformations of the structural floors, which are unavoidable due to the movement of the building, mean that structural connections between the floors and the stair are impossible. The solution was to build a structurally independent staircase. Two steel columns in the stairwell, rigidly fixed at the base but with sliding connections at the floors above, form the primary structure. The steps are suspended between the glass stringers, which are bolted to the steel columns via T-shaped glass fins. The landings do not transmit any loads to the floors; instead, there is a sliding joint that isolates the stairs from the movements of the building. At no other point does this apparently lightweight construction make contact with the adjoining building components. As the staircase does not have to accommodate the movements of the building, it can be supported entirely on the 51st floor.
And it was not only the structural engineers who made use of a few tricks. The special circumstances of this project had to be considered during erection as well. Only a standard passenger lift was available for transporting the individual components to the top of the building! All the elements therefore had to fit into this lift car. seele sedak GmbH & Co. KG in Gersthofen/Germany fabricated all the glass components – steps, stringers and glass fins – and their fixings plus the erection scaffold, and delivered everything to Philadelphia.
Four large-format video screens are incorporated between the columns, which are encased in sheet metal and clad with glass. The screens merge with the all-glass construction of the stairs to form one architectural entity without obstructing the magnificent view across the skyline of Philadelphia.