First of Kind in U.S. : UCSD Readies Quake Testing Lab

Sometime next year, the slow, deliberate destruction of a reinforced concrete masonry building will begin at UC San Diego in the first earthquake research test of its kind in the United States.

The results could bring improvements in design and construction methods for many buildings, especially in the Western United States, and thereby reduce substantially the numbers of estimated casualties and property damage from a major quake. A large temblor might kill upwards of 20,000 people in Southern California, depending on the time of day and location of the quake, according to federal government predictions.

The key element is a new testing lab under construction at UCSD, which will feature an 18-foot-thick, 50-foot-high concrete wall known as a strong-back, or reaction wall. Scientists will be able to construct a full-scale building up to five stories tall and 50 feet wide next to the wall and, by positioning hydraulic rams between the wall and building, create earthquake-type forces.

Until now, the only reaction walls to test full-size buildings have been built at a national science center in Japan, where a joint U.S.-Japan earthquake research program already has tested full-scale buildings of steel and of reinforced concrete.

“This will be the first lab in the U.S. where we will be able to verify computer simulations developed to determine whether a building is designed adequately for earthquakes,” Gilbert A. Hegemier, a UCSD engineering professor who has spearheaded efforts to build the facility, said. The lab is being funded jointly by UCSD and the National Science Foundation, and will be available to researchers nationwide.

“No one knows for certain that the (computer) simulations are accurate,” Hegemier said, although both he and Frieder Seible, an assistant professor working on the project, stressed that the lack of confirming data does not mean all present buildings are therefore unsafe.

“We’re not saying that the tests will show designs are wrong, but rather that there are probably ways to make buildings safer,” Seible said.

James Noland, a Colorado engineer coordinating the masonry portion of the U.S.-Japan project, added: “You can never predict 100% with simulations.”

Noland participated in a federally-sponsored workshop last year which reported that carefulness in design has generally compensated for the limits to simulations.

“That . . . has usually been successful,” the workshop concluded. “Many more buildings in the U.S. have survived strong shaking than have been destroyed.

“But the process is not reliable enough to ensure public safety to the degree expected, nor is it the most economical approach to hazard mitigation.”

Earthquake research on building design in the United States has traditionally been carried out through testing individual components of a structure, such as the walls, or floors, or the intersection of a beam and a column, using machine application of various forces. In addition, scale models of buildings--from one-third to one-fifth actual size--are subjected to earthquake-type movements by placement on computer-controlled shaking tables, the largest of which, at UC Berkeley, measures 20 feet by 20 feet.

“A shake table comes closest to actually simulating an earthquake,” Hegemier said. “But because you have to use a scale model, there can be difficulties.” Although steel can be scaled down with good accuracy, there is much more of a problem with brittle materials, such as concrete or brick, he said.

Because reinforced concrete masonry usually includes steel reinforcing bars running through the hollow centers of concrete block, researchers often encounter problems in scaling down materials in terms of chemical composition. Concrete consists of sand and gravel bonded together with cement, and there is difficulty in accurately making so-called “microconcrete,” using scale rocks and sand.

Also, researchers are not certain that materials and components, when tested separately and then combined for performance only through mathematical models, will behave as predicted when subjected as a single mass to an earthquake.

The strong wall facility has an advantage over a full-scale shaking table in being much less expensive. The UCSD facility will cost about $2 million to construct and another several million to equip. By comparison, a shaking table large enough to accommodate a full-scale five-story building would cost upwards of $200 million, according to John B. Scalzi, an engineer with the National Science Foundation.

Despite the relative low cost of a strong wall lab--and desire for it by researchers--the idea for the UCSD facility did not develop in detail until early last year.

At a February 1984 conference in Pasadena, American researchers decided that the concrete masonry portion of the U.S.-Japan project should be tested in the U.S. This is because masonry is not a uniform material, but one that depends on workmanship and the available components. Those qualities differ greatly between the two countries, and results could be applied more widely in the U.S. if the full-scale test could be done here, the participants reasoned.

At first, the UCSD lab was envisioned only as a facility for pounding and shaking large-scale components, funded with a $1-million grant from the Powell Foundation in Los Angeles. But with the need for a full-scale strong wall to do masonry testing, scientists decided to try and tap the National Science Foundation for additional funds.

“It was at UCSD’s initiative, but we extended the facility (by providing $835,000) to be more acceptable for nationwide research,” Scalzi of NSF said.

The total cost of the building is being kept down by constructing it as a package with a new magnetic research recording lab. If built separately, the cost might double.

“This is a good deal for everyone,” UCSD’s Hegemier said. “If built from scratch, this lab might cost $10 million or more. From the university’s standpoint, we have much more than we initially planned.” Furthermore, UCSD has only recently established a structural engineering studies program, and the new lab will be a visible jewel in attracting students and professors.

The earthquake lab will resemble a large movie theater from the outside, with 120-foot-long sides and a 64-foot clearance from floor to ceiling. Inside, the floor itself will be raised eight feet from the foundation, so that forklifts can be driven under it to position hydraulic rams for testing large-scale bridges and other components that need to be anchored to the floor before they are pushed and pulled.

The strong wall will be at one end of the building, in essence functioning as a floor raised perpendicularly. Rams will be connected from the wall to a full-scale building. The wall, because of its massiveness, will remain immobile despite the pushing exerted between it and the building. As a result, measurements made of the building’s reactions to various forces will not be skewered by movements in the strong wall.

The testing of the first building will take place over a year’s time. The hydraulic rams will be programmed to exert certain forces based on data developed from previous component testing and from actual earthquakes. Depending on how the building reacts to the strain, subsequent simulations will be revised. Cracks or damage to the structure may be repaired and reinforced, and tested again to see if improvements will better withstand earthquake-type forces.

“This testing is analogous to turning on a radio to see if it works,” Hegemier said. “You don’t have to check every single station on the dial. In the same way, you want to know if the building works . . . but you don’t need to test every conceivable type of quake.”

Already, results from the earlier steel structure and reinforced concrete tests in Japan indicate that improvements are needed both in some design areas as well as in workmanship.

“Some parts of the (Uniform Building Code) will need to be strengthened, no doubt about this,” said Vitelmo Bertero, UC Berkeley engineering professor overseeing the U.S. portion of those tests.

“We found that there has to be better application of the code, that you must have good construction, good quality control . . . and design beyond the minimums of the code; for example, in deciding how you anchor a reinforcement from a beam to a column.”

Bertero said that much of the code is based on analysis expressed in mathematical equations, which have not been verified in all cases by the experimental full-scale testing.

“We have shown that if you are careful in applying the code and careful in recognizing where building weaknesses are (in responding to earthquakes), then you have a building that is safe.

“But the data shows that you don’t have a lot of room for error.”

Researchers are particularly interested in the results from the concrete masonry testing at UCSD. Such buildings are economical and convenient to construct and are energy efficient. Reinforced concrete masonry buildings account for 90% of all warehouses and supermarkets in California, Hegemier said. They should not be confused with buildings made of unreinforced masonry, such as hollow tile, which were common for years in California, but suffered severe damage in the 1932 Long Beach quake and have been avoided since.

“Masonry is harder to understand than steel or reinforced concrete, so I hope for a lot of information,” Berkeley’s Bertero said.

By indicating where design needs to be improved or is adequate, the tests will allow greater economy to be built into structures by permitting use of less materials. Materials suppliers such as cement and steelmakers are supporting much of the research.

All the researchers emphasize the need for getting the information into the hands of structural engineers as soon as practical. Ultimately, the data must be incorporated into building codes.

“You cannot rush research,” Bertero cautioned. But he is hoping to get the results of the steel and reinforced concrete data disseminated soon. He is scheduled to speak next month on the tests results to the American Concrete Institute and already has authored several monographs on the Japan-based projects.

For Seible, the bottom line is, “For a little bit more money, we can make buildings a lot safer.”