Uc san diego experiment is first of its kind in u. S. : new test lab to measure quake impact on buildings

LA JOLLA — Sometime next year, the slow, deliberate destruction of a reinforced concrete masonry building will begin at the University of California, 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 West, and thereby reduce

substantially the casualties and property damage from a major quake. A large temblor might kill more than 20,000 people in Southern California, according to federal government predictions.

The key element in the new testing lab under construction at the university is 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 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,” said Gilbert A. Hegemier, an engineering professor who has spearheaded efforts to build the facility. 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. 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 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. Earthquake research on building design in the United States has traditionally been carried out by

testing individual components of a structure, such as the walls or floors, or the intersection of a beam and a column. 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 one, 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. Concrete consists of sand and gravel bonded together with cement, and there is difficulty in

accurately making so-called “microconcrete,” using rocks and sand to scale. Effects of Combinations Also, researchers are not certain that materials and components, when tested separately

and then combined for performance only through mathematical models, behave as predicted when subjected as a single mass to an earthquake. A strong-wall facility of the kind UCSD is building

is much less expensive than a full-scale shaking table would be. The facility will cost about $2 million to construct and several million more to equip. By comparison, a shaking table large

enough to accommodate a full-scale five-story building would cost upwards of $200 million, John B. Scalzi, an engineer with the National Science Foundation, said. 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 fork lifts can be driven under it to position hydraulic rams for testing. 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. One-Year Test Period 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 design and workmanship. Need for Revisions “Some parts of the (Uniform Building Code) will need to be strengthened, no doubt about this,” said Vitelmo Bertero, a UC

Berkeley engineering professor overseeing the U.S. portion of those tests. Researchers are particularly interested in the results of 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. MORE TO READ