This five-level precast concrete parking garage is part of an innovative new health center at the University of Pennsylvania. The underground structure supports half of the 17-story, 1.5-million ft² steel patient center, which will house 500 private patient rooms, 47 operating rooms, and a 61-room emergency department.
Constructed 67 ft underground, the parking garage includes 689 parking spaces to serve the patient pavilion, two stair towers, a series of elevator shafts, and two precast concrete cisterns, as well as provisions for fuel tanks, a network, locksmith, materials management, and IT.
The designer chose precast concrete for the project in part due to the speed of erection it would afford the larger initiative. However, digging 67 ft underground to build a parking deck that would eventually support half of the 1.5 million ft² structure created several challenges.
The first was proving the precast concrete design could support the weight of the structure. The designers were confident it would work, and in-depth study proved them to be correct. The design solution was to emulate a cast-in-place concrete design with precast concrete elements so that the structural performance is equivalent to that of a conventionally designed, cast-in-place, monolithic concrete structure.
Six Million Pounds
The new garage was designed and detailed to meet the requirements of the applicable building code as if it were to be constructed of monolithic cast-in-place reinforced concrete. However, the structure was divided into structural elements of sizes and shapes that could be plant fabricated, transported, and safely and efficiently erected on site. This method is consistent with American Concrete Institute (ACI) 550.1R-09, Guide to Emulating Cast-in-Place Detailing for Seismic Design of Precast Concrete Structures, and is judged by ACI to be applicable to any structural system where monolithic structural concrete would also be appropriate.
The above-grade patient tower is supported primarily on below-grade precast concrete framing. To support the massive pavilion, many of the typical columns had to be designed for loads in excess of 6 million pounds. Typical precast concrete columns were 33 in. by 66 in. using 9000-psi concrete.
The pavilion’s lateral force–resisting system is primarily composed of steel-braced frames around the stair and elevator core. At the transition from above-grade steel framing to below-grade precast concrete framing, the steel-braced frames distribute loading to precast concrete shear walls beneath. Lateral loads from the pavilion are also distributed into the below-grade floor diaphragms to the below-grade columns and perimeter walls.
This innovative use of precast concrete significantly accelerated the construction schedule and allowed work on the massive steel patient pavilion to begin sooner than would have been possible with cast-in-place concrete construction.