Project Overview
As the new centerpiece of the Albert B. Chandler Hospital at the University of Kentucky in Lexington, Pavilion A celebrates the art and science of medicine, providing the very best care within a healing environment that conveys the unique spirit of the state.
The new 1.2 million ft
2
(111,000 m
2
) facility serves as the front door to the hospital campus, unifying the complex and creating a new focal point as visitors arrive, says Thomas Gormley, principal at GBBN Architects. "As the new hospital nexus, it needed a dramatic appearance that blended with the existing buildings on the college campus."
"The university realized that they were embarking on a facility that would set the stage for healthcare at the University for many years, not just to fulfill an immediate need," Gormley says. The owner made sure the University HealthCare's guiding principles, which focus on patients, staff, students, and technology, were used as a basis for all design and construction decisions.
One of the biggest challenges for the design team was finding a way to build an attractive, durable structure that could be enclosed quickly so trades could begin working on the complicated interiors and still maintain the tight schedule. "The exterior skin of the hospital was a large part of the construction's critical path," he says.
Precast Solution
The team reviewed a variety of skin options, looking for one that would provide the most efficient thermally performing exterior skin and accommodate an accelerated construction schedule, says Mark Pedron, vice president of operations at Gate Precast. They ultimately chose a high-performance precast concrete design after seeing how insulated precast concrete panels could meet the exterior-design objectives, offering edge-to-edge continuous insulation and a blend of five types of textures and colors to mimic the handset-brick and stone used on adjoining buildings.
The team visited several precast concrete installations to evaluate options and validate that the system could achieve the project's exterior-design objectives. "The architect wanted a building that had continuous insulation with no cold spots created by building material techniques, not allowing any bearings or connectors to interfere with the consistency of the insulation layer," Pedron says. "Additionally, the exterior precast concrete cladding offered a quality of construction that could be better controlled and still take a significant amount of time off the project schedule."
The precast concrete panels consist of a 3 in. (75 mm) front wythe of concrete with another 5/8 in. (16 mm) layer of thin brick, a 2 in. (50 mm) center of polyisocyanurate insulation with ship-lapped edges, and an interior 4 in. (100 mm) structural wythe. The resulting panels are 6 ft 8 in. (2.03 m) tall and 36 ft (11 m) long. A vapor barrier was laid over the insulation prior to casting the interior structural wythe of concrete on top to add further performance attributes to the skin.
Prestressing was also used to strengthen the panels, Pedron says. "Due to the large sizes of the panels and the thinness of the wythes, prestressing added sufficient strength to ensure the forces created by stripping the panels from the molds would not crack the panels."
To shorten erection time as much as possible, the project schedule was broken into two shifts. "We were able to set precast components during the second shift, which allowed the other trades to use the cranes during the day," Pedron says. This allowed concurrent work, which helped cut time from the construction schedule and allowed the erection crew to enclose the structure in significantly less time than by other conventional construction methods and materials.
"If they had tried to use hand-laid brick, it would've taken forever to get it completed, and the site-at the front of the hospital-would have been disrupted for a long time with materials and scaffolding," says Bill Sparks, chief engineer at Gate. He estimates the precast concrete panels allowed the building to be enclosed two to three times faster than would have been possible with laid-up brick, without the site congestion. |