Stability Engineering provided structural design, construction documents, and construction oversight for the adaptive re-use of two 8-story office buildings in downtown Atlanta to become multi-use commercial and residential spaces. The two buildings served as the headquarters of the Southern Railway and Norfolk Southern Railroad Company from 1912 to 2004. The original base levels of the two buildings were constructed in 1912, with subsequent vertical additions in 1928 to achieve the current height. Structural items for the adaptive re-use and restoration included an extensive evaluation of the existing concrete frame structure for repairs and seismic upgrades, replacement of removed columns at upper floor levels to allow for the removal of spanning hanger beams at the roof, creating new floor openings in the building for mechanical chases and connecting of stairwells and elevator shafts, as well as extensive concrete repairs and infilling of old floor and roof penetrations. Building improvements also included coordination with veneer and building envelope specialists for repairs to the facade and parapet walls at the roof level.
Additional structural design items for the project include the streetscape improvements along Ted Turner Drive, which involved repair and reinforcing of the existing walkway and parking bridges connecting the building to the street over the lower level alley, as well as new steel bridges and cantilevered sidewalk extensions. Design challenges presented with this project included working with and around a variety of existing conditions, which required significant reinforcing of several structural conditions. The project also required working around the pre-existing Nelson Street Bridge, which runs between the two buildings and below the connector “skybridge.” The skybridge connection between the two buildings required re-supporting on one side onto new full-height steel columns with slip connections to allow for differential movement between the two buildings. Additional structural coordination with the surrounding site included accommodation of underground trenching for utilities in proximity to the existing building foundations, as well as a new small building structure to house a GA Power substation and coordination of the placement of streetlights with the City of Atlanta along the Ted Turner Streetscape and sidewalk extensions.