The new office building at 1200 Intrepid Ave., in the Philadelphia Navy Yard Corporate Center is a sight to behold, described by some as gravity defying in that parts of the structure are designed to replicate the shape of a ship's hull, narrow at the bottom and wide at the top.
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Location: New Brunswick, N.J.
Type of Precast: Structural precast
Size: 632,000 square feet (278,000-square-foot parking garage)
2014 PCI Design Award Winner: Honorable Mention, Retail Structures
Images courtesy of Meltzer Mandl Architects and Severud Associates
Smart growth development is based on a precast parking garage
Transit-oriented development helps municipalities create attractive, vibrant, pedestrian-friendly neighborhoods where people can live, shop, work, and play without relying on automobiles. Residential housing options constructed within walking distance of an existing transit facility increases transit ridership while reducing traffic congestion and improving air quality.
In a recent and unconventional interpretation of this concept, the New Brunswick Development Corporation (Devco) has completed Gateway Transit Village, a mixed-use, transit-oriented design consisting of a 24-story building and a new pedestrian walkway directly adjacent to a NJ Transit/Amtrak station. Located in the heart of downtown New Brunswick across from the Rutgers University campus, the new $150 million, 632,000-square-foot structure is the tallest building in the city. A precast parking structure from High Concrete Group LLC forms its core.
Built as part of an ongoing revitalization effort, the new complex is intended to help bring renewed life to a site that is vital to the city, but that has been under-utilized for many years. With views of the Raritan River, the apartments and condos in the tower are targeted to attract people who already live and work in New Brunswick. Twenty percent of the units are set aside for moderate- and low-income owners.
The project is unconventional in several ways. "Gateway is the most urbanly dense transit village in New Jersey," notes David J. Stuart, project manager for New York City-based Meltzer Mandl Architects. "Everything that’s normally incorporated into a transit village has been combined into a single structure."
"Also, precast concrete parking garages are not typically designed to support taller and more complex structures above them; they are usually stand-alone buildings. To place a 14-story building on top of a garage is daring structural engineering," says Stuart.
Gateway Transit Village consists of a 10-story precast parking garage with 697 parking spaces, topped by a 14-story steel-frame and hollowcore residential tower containing 150 apartments and 42 condos. The structure is wrapped by 120,000 square feet of offices and a series of street-level commercial spaces for tenants, including the Barnes & Noble College Bookstore for Rutgers and offices for the New Brunswick Parking Authority and the Rutgers University Press.
Stuart notes that Gateway Transit Village doesn’t relate to its context as much as redefine it. "A typical approach would be to hide the parking garage, and disguise the precast," says Stuart. "At first we considered thin brick, to match other parts of the structure. But we decided that we wanted an exposed concrete aesthetic for the podium, to let concrete be concrete, and to show its inherent nature. Precast concrete can be quite elegant, minimalist. It was economical, fast, and gave us pleasing aesthetics."
The majority of the garage was cast in a standard High Concrete Group buff architectural mix and finished with a light sandblast. Simple reveals set up a rectangular pattern that brings scale to the horizontal spandrels and complements the openings between them on the way up. Spandrels at the top are finished with a small cornice.
The parking garage required 24-foot and 36-foot spacing between the support walls to optimize the parking spaces and 12’-wide precast double tees. The residential tower called for a different supporting grid, which had to have its column lines aligned with the garage support walls via 10-inch-thick hollowcore plank spanning up to 36 feet.
"This is a good use of precast," says J. Benji Alper, PE of engineering firm Severud Associates’ New York office. "While the precast garage is only 10 stories, the overall structure still stands at 24 stories tall, requiring the precast walls to resist the forces for the full lateral and gravity loads of the 24-story building." He discusses the approach in the Structure Magazine article,"Integration of Diverse Structural Systems and Design Delegation in a Mixed Use Space."
Alper notes that communication was critical in the project. "Immediately after the contract award, weekly meetings were conducted with the entire design team which included members from the precast manufacturer’s engineers, the structural engineer, the architect, the parking consultant, the owner, and the general contractor. Other trades, including the steel fabricator, the steel detailer, and the erector, also would often attend. The meetings were a key part of an iterative design process between Severud and High Concrete Group."
In the iterative design process, changes to the lateral walls in the garage would result in changed stiffness values at the base of the residential tower, redistributing loads within the steel tower structure. Connections between the steel tower and precast structure required a high level of detailing by the structural engineer of record to ensure complete coordination between steel and precast fabricators. The final design by the precaster relied on 24"-thick shear walls constructed with 10,000 psi precast concrete with up to 44 #11 reinforcing bars on each end.
The precast concrete structure provides clear spans required for unobstructed parking while also providing the city parking authority with a low-maintenance structure. The ease of erection of the precast system helped reduce the overall cost of the garage levels. The high strength, densely reinforced walls reduced field labor by concentrating the load in a lesser number of walls instead of requiring additional field connections to engage additional structural elements, thereby yielding a more economical design.