Prefabrication Process

To create the panels, Coreslab used large flat casting tables with smooth fiberglass surfaces and side rails around the perimeter. The cold-formed steel framing was prefabricated into the required panel sizes, and the Metal Stud Crete shear transfer strips were screwed to the faces of the studs.

The framing was then set into the forms and secured in place above the casting table so that concrete could be cast to the required thickness. In some panels, it was necessary to pour the concrete first and then set the frames onto the concrete.

While the precast concrete is very thin, the designers wanted to recess the entrances and windows thirty inches (760 millimeters) to make the walls look thick and massive and to create dramatic shadows, as in the original building (Fig. 5.8). Fabricating the deep returns required ingenuity to preserve the high-quality finish of the panels, and Coreslab chose to form the recesses in a two-step process.

 

Figure 5.8 - Deep returns were fabricated in the panels to create the image of thick traditional masonry walls

 

First, they poured the concrete for the panel returns in a downcast position. The panel returns were then rotated into a vertical position and set into place in the forms so the panel faces could also be downcast. As a result of tight quality control, no pour lines or joints are visible at the transition between the two surfaces. Altogether, 325 precast components were cast and assembled to create a total of 146 building panels.

The architectural precast concrete contains integrally colored concrete and light colored aggregate. With a light sandblasted finish, the panels look like fine honed limestone.

The very large panels enabled almost all joints between panels to be concealed by architectural elements; vertical joints occur at changes in wall plane and horizontal joints are behind belt courses and cornice moldings. The result is an almost monolithic appearance, as if the entire building had been sculpted from a single massif of limestone.

Paul Clark, Jr., vice president of Metal Stud Crete, says this technology has been used to produce over two million square feet (186,000 square meters) of precast concrete panels, ranging from one-story load-bearing tilt-up walls to curtain-wall cladding for highrise buildings.

Konoske credits the Metal Stud Crete system with allowing the period look to be achieved. And, given the project's technical requirements, this system was the only viable choice. "Metal studs and precast concrete is a nice marriage," Konoske says, citing strength, thin profile, and appearance.

The Research Center was completed on time and within budget. England says exterior walls accounted for just $1,500,000 of the project's $20,000,000 construction cost. Prefabrication began while the steel structure was being installed, and erection proceeded immediately after. The panels were installed in less than two months.

The technicians working in the labs and the scholars pouring over precious documents in the Huntington Library recognize the many benefits of the new structure. And thousands of visitors walk past the addition every day without recognizing that it is a new structure, so well does it harmonize with the traditional architecture of the institution's other building