Bettering Our Odds to Arm-Wrestle with Mother Nature : Earthquakes: New technologies may bring us structures that not only protect life, but limit the damage, too.

I think it was Chris Arnold, an architect from San Mateo, who first described earthquake engineering as “arm-wrestling with nature.” This is because engineers, architects and earth scientists are all involved in confronting and containing the destructive power of a major earthquake.

Not knowing the location and magnitude of the next earthquake is one of the quirks of the game. Not having a warning is another.

Conventional wisdom dictates that we should stand and resist these overwhelming forces with rigidity and great strength. We also know by sad experience, however, that earthquake forces are strong and that we cannot construct an earthquake-proof building at any price. The nuclear industry comes close to this ideal when it builds billion-dollar power plants. But neither the private nor commercial sectors can afford such costs. So we must reconsider how our structures can resist earthquake stress and what we can expect of them during an earthquake.

A realistic approach is to accept damage as inevitable, but to confine it to areas where it can be controlled and managed to advantage.

Structural engineers, building officials and others familiar with modern building codes know that this strategy is inherent in our current seismic design provisions. Recognizing the overwhelming stress that a major earthquake can place on a structure, the codes accept the idea that damage-free response is an unrealistic goal. Instead, life safety is their objective. Modern codes therefore do not promise an earthquake-proof building or bridge, only that it should not collapse and kill people.

Engineers know that to achieve this objective, their structures should behave in a ductile, not brittle, manner. Steel is an example of a ductile material; concrete is known to be brittle. During the last 20 years, researchers have developed methods to reinforce concrete so that it, too, will behave like steel. Bridges built since the mid-1970s include these new details, but older structures are not ductile and will suffer, perhaps catastrophically, when tested in a large earthquake.

Accordingly, there is an urgent need to upgrade these structures. The goal of any viable retrofit scheme must be to prevent collapse and to preserve life--and be cost-effective.

Arm-wrestling with nature is more than just a game. It is life itself. So long as we choose to live in large metropolitan areas along or above active fault systems, we live with the hazard daily. As noted earlier, some of the rules of the game are known, but others are not. Each time we play, we learn something and, as a result, have the opportunity to improve the state-of-the-art.

Perhaps now is the time to re-examine the philosophy of our design codes. Is life safety alone good enough? Do we have a right to expect more from our structures? Does the technology exist to do it better? If not, why not? These are reasonable questions.

Yes, earthquake loads on structures can exceed the strength of common engineering materials, but in this high-tech age, is there not another alternative? One promising development is the recent advent of earthquake protective systems that substantially reduce the seismic forces in a conventional structure and thereby eliminate the need for greater strength.

Damage-free performance is attainable for a wide class of structures. An example of such a system is the seismic isolation of the new Los Angeles County/USC hospital. Another is the active control system now being tested in a building in Tokyo. This concept gives a building the “intelligence” to react to external loads in such a way as to “save” itself, as we all do when we trip going up the stairs. Active control is a product of research conducted in the United States, but it is being implemented first in Japan because of a reluctance in this country to embrace new and radically different structural systems.

Acceptance of seismic isolation design also is slow in the United States. Yet both of these protective systems offer more than just life safety; essentially, they offer elastic performance within reach and at modest cost.

Both offer the ability to radically better the odds when we are forced, once more, to arm wrestle with Mother Nature. Lessons learned during the Oct. 17 earthquake are both painful and costly. But if we do not learn from this and improve our game plan, we have nobody to blame but ourselves.