Center 128 Parking Garage
The large glass curtain wall surrounding the elevator and stair core in one corner of the seven-story Center 128 parking structure provides a signature look for the facility both during the day and night. It also created some challenges that the precaster had to solve aesthetically and structurally to make the design a success.
The parking structure was built in tandem with the Center 128 office complex, a series of four buildings containing approximately 740,000 square feet of LEED-certified office space. The total-precast concrete parking structure contains 300,000 square feet of space for 1,047 cars, which will support the first of the office buildings planned for the site.
The challenges with the glass-enclosed stair and elevator tower arose due to the openness desired by the designers, explains Peter Bertolini, project manager at Blakeslee Prestress, the precaster. Some of the stair units required the internal columns to cantilever off support columns to provide the open look. “It required significant design and coordination for that element to meet what was required because of the desire to have nothing protruding into the area to obstruct the look.”
The precast concrete beams had to be threaded between columns with long arms protruding to support the stairs. Haunches and connections to the stair towers were concealed to ensure the aesthetic design was not obstructed inside the tower. “Other than that aspect, the structure had a fairly straightforward design.”
The parking structure features a total-precast concrete structural system, consisting of double tees, girders, columns, shear walls, lite walls, spandrels, stairs, slabs, and wall panels. The structure’s long columns had to be cast in segments and spliced together at the site, as their length precluded transporting them as one unit, Bertolini notes. Spandrels feature a combination of white and gray cement with reveals used to add interest and hide joints.
Once the precast concrete structure was erected and the stairway was completed, crews took field measurements before crafting the curtain wall to ensure tolerances were precise. That approach also was taken for copper cladding that serves as a feature element around the curtain wall. The cladding wraps around the outside and into the interior core. The goal was to provide a rich, tactile material at the points where users would be closest to the exterior walls.
The site presented only one challenge, in power lines that had to be moved out of the way. The erection started at the farthest point away from the lines, maximizing the time available for the power company to make the adjustment.
The parking structure is scheduled to be completed in February 2015 with the office buildings to follow. The parking will serve the first office building and will be expanded horizontally as demand for office space allows for construction on the next building to begin. As demand grows, a third and fourth office building will be built, with a second, smaller parking structure constructed in a similar fashion to serve those buildings. The first building is fully leased and will be ready for occupancy late in 2015.
Structural Precast Elements:
• 402 Double Tees
• 34 Girders
• 54 Columns
• 32 Shear Walls
• 40 Lite Walls
• 144 Spandrels
• 21 Stairs
• 31 Slabs
• 38 Wall Panels