Channel Center Parking Garage
The Channel Center Parking Structure in Boston will have a dramatic exterior design when it is completed later this year, in keeping with its urban setting near office buildings and residences. The design features a total-precast concrete structural system serving as the palette onto which several aesthetic treatments, including brick, sheer metal mesh, and curtain wall inlaid with colored glass, will be laid.
The nine-story, 300,000-square-foot structure includes parking for 967 cars, as well as parking for 100 bicycles and 10 electric-vehicle charging stations. Those new spaces provide a significant benefit to alleviate the area’s congestion. But fitting this large facility into the urban landscape required more attention to aesthetics than may be typical, says Cheryl Tougias, principal at the architectural firm of Spalding Tougias.
“This is a large building, and we needed a structural design that was economical but that could also form the base for the various aesthetic treatments we wanted to use,” she explains. “The precaster joined the process early on a design-assist basis to ensure we could create a plan that could be fabricated and erected quickly and that could address all of the design goals.”
The structural system consists of precast concrete double tees, girders, columns, k-walls, shear walls, wall columns, spandrels, stairs, slabs, and wall panels. The K-walls serve to support loads along the perimeter of the structure, allowing more open interiors that enhance layouts and provide visual openness that improves security.
The wall panels offer structural support backing for full-size brick that was laid in large vertical swaths along the facade facing the street. It also was used with precast concrete panels facing the elevator and stair core and at the entry points. “We used the brick to provide a more human scale to the building,” she says. Dovetail joints were provided in the precast panels’ faces to ensure a secure connection to the bricks.
Interspersed with these brick faces will be sheets of perforated metal mesh, creating a light scrim that rises from the base to the top of the building and contrasts with the solid, durable precast concrete. The panels behind this material were cast with embeds to connect to metal brackets that hold the metal sheets. The panels also include embeds for color-changing LED lights that will wash the metal screens and project uplighting onto them.
The lighting will produce vivid effects as the colors and shadow lines interact. This is emphasized further by the use of colored glass inserted into curtain-wall segments. “The lighting adds life to the building throughout the day,” she explains.
“Precast concrete provided a good, solid container for the variety of aesthetic designs and a contrast with them,” she says. “We thought the finish on the concrete looked very expressive, so we didn’t use a pigment or texture on it. We wanted it to express itself as concrete.”
The structure, which will be completed by the end of 2013, has been moving smoothly through its erection, which began in April and lasted into July. The 300-ton crawler crane was placed on crane mats due to the poor soil conditions. It was configured to meet the distance and capacity challenges for the high structure.
The crane erected the structural two bays at a time to its full height. Maintaining plumbness between bays posed a challenge, especially with the jump columns and jump wall columns. Welding and grouting operations had to be coordinated immediately behind the erection to maintain stability. A key challenge came in aligning the pile and grade-beam foundation system with the connections to the precast columns, but that moved forward without a hitch.
“The ability to provide essentially single-source responsibility for the structure was a key benefit,” she says. “There really needed to be little interface with other trades, which has sped up construction. We are very happy with the precast and with the economy and the speed it has provided to the project.”
Timeline: Contract Award – Blakeslee August 1, 2012
Start Precast Erection – April 24, 2013
Complete Precast Erection – July 25, 2013
Structural Precast Elements:
• 392 Double Tees
• 18 Girders
• 34 Columns
• 20 K-Walls
• 10 Shear Walls
• 28 Wall Columns
• 140 Spandrels
• 18 Stairs
• 5 Solid Slabs
• 89 Wall Panels