BERKELEY, CALIF. — A major California university is using a customized reinforcement system in an effort to preserve a historic 93-year-old vaulted ceiling. The elements include fiberglass-reinforced-plastic structure, steel mesh and polyurethane foam.
The work is a miniscule but important part of a much larger restoration project on the University of California's oldest campus, located in Berkeley.
Construction started in the spring of 1999 at the Hearst Memorial Mining Building and is scheduled for completion by the end of 2001.
Finding workable concepts demanded solutions from a project team representing the building owner, architect, structural engineer, contractor and a polymer molding architectural firm.
"The project team as a whole searched for and developed not only this technology for the strengthening method but the means and methods of getting it in place," said Rob Gayle, assistant director of project management with the university's capital projects division.
The installation has about 4,800 face tiles on the curved vault and architectural pendentives and 1,500 on the vertical walls, according to Julie Steier, project manager with William Kreysler & Associates in Penngrove, Calif.
"The strengthening method for the Guastavino tiles is probably the most unique example in technical terms, [and is] not being done anywhere else," Gayle said in an interview at his job site office. "It is taking a technology that has obvious capabilities and molding it literally to do something that it never has done before."
The solution "is applying basically cutting-edge technology in the service of preservation," Gayle said. "We're using late 20th-century technology in order to preserve late 19th-century technology."
The San Francisco firm of Rutherford & Chekene served as consulting engineers.
"We did not want to use conventional construction techniques to strengthen the ceiling because of the thin and brittle nature of the clay tile vaults," said Doug Robertson, who managed the project for R&C. "Instead, we wanted a more high-tech solution such as a polymer system."
The unreinforced masonry building is the campus's "most important building historically and architecturally," Brendan Kelly said during a tour through the construction site. Phoebe Apperson Hearst financed an international design competition for the university's new campus. The building, the first for that design, was built for $1 million as a memorial to her husband George Hearst, a successful mine operator, publisher and politician, who died in 1891.
Their son, the legendary William Randolph Hearst, was running for governor of New York when the university opened the building. At the time, one-fourth of the students at the university pursued degrees from the College of Mines.
Kelly, a project architect with NBBJ of San Francisco, calls the effort "a hat trick" involving seismic retrofit, laboratory-classroom-office improvements and "a restoration to the 1907 grandeur of the building."
The Hayward fault lies about 750 feet to the east of the building.
The entire project's budget approaches $70 million. Work on the herringbone-patterned Guastavino "is less than 1 percent of 1 percent of the total project," Kelly said.
On a historic basis, the vault construction process of Rafael Guastavino y Moreno and his son advanced a centuries-old building method called the boveda catalana, or Catalan vault. The Guastavinos brought their technique — laminating courses of tile with mortar — to New York from Spain in 1881 and earned many prominent commissions.
Their style exists in many religious, commercial, government, education and residential buildings in the East, but fewer examples are located in the earthquake-vulnerable West. San Francisco's stock exchange building and the Grace Cathedral are two sites in addition to the Hearst building.
In Berkeley, the barrel-vaulted ceiling surrounds three round skylights and is located atop a grand four-story-high entry hall. The setting emulates an abstracted mine shaft and honors George Hearst, one of the renowned gold-rush forty-niners.
Lights under the truss beams mimic a mine's illumination at night, and filtered natural light from the sides and above brightens the hall during the day. Changes in the lighting create a range of shaded patterns on the tiles.
Kelly said the project "is the first seismic retrofit of a Guastavino system."
Workers will remove part of the roof above the fragile Guastavino ceiling for access.
They will install a diaphragm including about 100 custom-made fiberglass I-beam ribs at 4-foot intervals and a layer of urethane foam both over the steel reinforcement mesh and at flexible points attaching each rib to the roof structure above.
Next, technicians using a low-vibration tool will drill a hole with a diameter of 0.125-0.188 of an inch through face tiles, backing tiles and wire mesh and into the urethane foam. Cost and technical considerations will determine how many holes are drilled.
The Kreysler firm lays up the ribs in open molds using Ashland fire-retardant vinyl ester resin reinforced with Vetrotex 1.5-ounce chopped strand mat, Knytex A260 unidirectional fabric and some Vetrotex 518-10 stitchmat, according to Serge Labesque, production manager.
"We are using standard roofing urethane foam with a higher density" of 5 pounds per cubic foot, said William Kreysler, the firm's president. "The adhesive properties are what we are after here. The load per square inch on the foam is very small, but the bond to the steel mesh is what is important. We did several tests and found the performance to be fine."
Ultraviolet degradation is not an issue for the indoor installation, Kreysler said.
"We kept telling Kreysler they could not have a rigid connection for the tile," Kelly said, "so they found this urethane connector." Workers will inject urethane elastomer matching the tile's color into each hole. A dot of makeup will conceal the hole in the face tile.
"We talked about using a metal pin, but the stresses between layers would fracture the brittle tile," Robertson said. A stress of 5,000 pounds might be exerted on a single pin. A urethane elastomer pin will stretch with the tile but retain the curvature of the arch, he said.
In a current undertaking, workers are installing 134 base isolators that will allow the building to move 28 inches horizontally in any direction. The isolators "give the building time to dissipate the energy when the earth moves very quickly and very violently," Kelly said. He likened the isolators to "a stack of rubber cards" functioning "like a slinky."
The isolation system exists, or is being installed, beneath 911-emergency-response telephone switching centers, hospitals and the Oakland, San Francisco and Los Angeles city halls. Base isolation was deemed a success where used in advance of the Kobe, Japan, earthquake.
The university is investing significantly in the foundation, "but it actually pays off everywhere in the building" since it reduces the amount of structural work required on the upper floors, Kelly said.